Characterising Anticipatory Postural Adjustments in Turning: A Comparison Between Healthy Older Adults and People with Parkinson’s Disease

Characterising Anticipatory Postural Adjustments in Turning: A Comparison Between Healthy Older Adults and People with Parkinson’s Disease | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Characterising Anticipatory Postural Adjustments in Turning: A Comparison Between Healthy Older Adults and People with Parkinson’s Disease Yuri Russo, Phaedra Leveridge, Jiaxi Ye, Zijing Wang, Alice Nieuwboer, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6172807/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 22 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 10 You are reading this latest preprint version Abstract Anticipatory postural adjustments (APAs) are crucial for maintaining postural stability during voluntary movements such as gait initiation. While APAs have been extensively studied in forward stepping, little is known about their characteristics during turning initiation. This study aimed to identify the characteristics of (i) APAs and subsequent first steps during turning in healthy older adults (HOA) and (ii) compare them to people with Parkinson’s (pwPD). Thirty-six pwPD (tested on medication) and 24 HOA performed self-paced uncontrived 360˚ turns which were embedded in a complex walking task. APAs and first step characteristics were recorded using motion capture and force plate data. For pwPD, APAs in turning were found to be primarily mediolateral, and of significantly reduced amplitude (median = .0065, 95% CI[.0053; .0089]) in comparison to HOA (median = .0110, 95% CI[.0073; .0181]). Unlike HOA there was no significant association between APAs and step characteristics. These findings suggest that APAs during turning are significantly impaired in pwPD, even when tested ON medication, and that this impairment may contribute to the turning difficulties often experienced by this population. Overall, these results have potential implications for clinical assessments and rehabilitation interventions, emphasising the need to tailor strategies to address turning challenges pwPD face in their daily life. Biological sciences/Neuroscience/Diseases of the nervous system/Parkinsons disease Physical sciences/Engineering/Biomedical engineering turn biomechanics APA step posture Figures Figure 1 Figure 2 Introduction Voluntary stepping movements are often preceded by Anticipatory Postural Adjustments (APAs). These preparatory adjustments rely on specific motor programmes generated by the central nervous system before the intended movement [ 1 , 2 ] to promote postural stability during the initiated step [ 3 , 4 ]. APAs are modulated according to environmental demands and conditions (e.g. time constraints, emotional state, base of support [ 5 , 6 ]). In forward gait initiation, APAs shift the centre of mass forwards and towards the standing limb i.e. unloading the stepping leg and preparing the body to accelerate forward [ 4 ]. APAs can be divided into two phases: imbalance and unloading [ 7 ]. The first promotes unloading of the stepping leg while accelerating the centre of mass forward, and the second represents the weight-shift associated with preparation for mono-pedal stance and heel-off. APAs preceding gait initiation are shown to be stable in healthy people [ 8 ] and are not significantly influenced by healthy ageing [ 9 , 10 ]. However, APAs are often studied in clinical contexts as they significantly influence first-step characteristics and walking performance [ 5 , 11 ]. Established evidence show that APAs are impaired in clinical populations [ 5 , 12 , 13 ], particularly in people with Parkinson’s (pwPD), where defective APAs contribute to difficulties with gait initiation [ 14 ]. In pwPD, falls often occur during attempted postural transitions such as gait initiation and turning [ 15 ]), when effective APAs are critical to successful and safe step initiation. Despite their potential clinical relevance [ 16 ], however, our current understanding of APAs primarily stems from studies on forward step/gait initiation, while non-linear postural transitions (e.g., lateral stepping, initiation of turning) have received little attention [ 17 , 18 ]. This is surprising given that many tasks in daily life involve turning while stepping [ 19 ] and that pwPD find it difficult to attempt turning tasks, even in early stages of the disease [ 20 ]. In addition, turning behaviour has been shown to be more abnormal in PwPD with freezing of gait [ 21 ]. Compared to forward gait initiation, turning is more complex as it requires simultaneous translation and re-orientation of several body segments, as well as posing challenges of postural control. It is therefore more difficult to study given the limitations of conventional biomechanical/clinical laboratories which are often optimised for gait analysis. By using VSimulators laboratory (VSimulators Exeter), we were able to largely overcome these limitations by designing a complex walking task that broadly resembles common real-world demands without sacrificing the use of gold-standard technology (i.e. motion capture and force plates). Our research aimed to: i) characterise APAs and properties of the first step during turning in healthy older adults; ii) compare these to pwPD; iii) explore whether there are asymmetries in APAs in pwPD when turning towards their most versus least affected side. We hypothesised that: i) APAs in turning would manifest primarily in the mediolateral direction, with small APAs in the anteroposterior direction; ii) similarly to that observed during forward gait initiation, pwPD would show longer and smaller APAs compared to healthy older adults; iii) we did not have a specific hypothesis regarding potential asymmetries in APAs between the most and least affected sides in PwPD. Methods Study Design This cross-sectional study characterised APAs and first-step characteristics in turning and compared these outcomes between healthy older adults and pwPD. All participants were tested at the VSimulators laboratory (VSimulators Exeter), University of Exeter, between March 2022 and October 2022. All participants with PD were tested while in their ON-medication state (~ 60 minutes after taking their regular dopaminergic medication). If necessary, participants were allowed to re-administer their medication to ensure they remained in their ON state throughout the testing. Participants Thirty-six pwPD and twenty-four older healthy adults were recruited through the Parkinson’s UK research network and the local community. Participants were eligible if they: i) were over 55 years old; ii) were able to walk unsupported for at least one minute. An additional inclusion criterion for the PD group was an existing diagnosis of idiopathic PD (UK Brain Bank Criteria). Exclusion criteria for all participants were: i) moderate cognitive impairment (Montreal Cognitive Assessment, MOCA, score < 21 [ 22 ]); ii) impaired normal or corrected-to-normal vision (Snellen Visual Acuity < 12/18); and iii) any injury or disorder (other than PD) that might affect balance or walking. pwPD were asked to answer the first question of the New Freezing of Gait Questionnaire (NFOG-Q, [ 23 ]) to self-identify whether they experience freezing. All participants provided written informed consent prior to participating in the study. The study was approved by the local institutional review board of the University of Exeter (21-12-08-B- 02, Department of Public Health & Sport Sciences). Procedure After providing written informed consent, participants with PD were assessed by a trained examiner (YR or WY) using the Mini-BESTest [ 24 ] and the Motor Section (Part III) of the MDS-UPDRS which consists of 23 items evaluating bradykinesia, rigidity, tremor, posture and gait [ 25 ]. They then underwent a walking test, designed to capture full body motion during turning and other elements of gait. The walking task was arranged in a square pattern with an external width/length of 3.6m x 3.6m. At regular intervals on each side of the square, a visual target of 15cm diameter was taped to the floor (see Fig. 1 ). The target was black and yellow and had a high visual contrast with the floor (light grey). Following an initial standing period, participants were instructed to walk forward and stop on the visual target. They were asked to pause for a few seconds, before performing a full 360˚ turn towards a self-selected direction (i.e. clockwise or counterclockwise) at a self-selected speed. On completing the turn, participants were asked to stop for a couple of seconds before walking through two cones (positioned ~ .2m and ~ 1 m from the outer lateral perimeter of the walkway and ~ 1.4m from the outer perimeter in the direction of the walking, to guide the navigation of the space), perform a 90˚turn, and continue walking until reaching the next visual target. To have uncontrived turning and avoid influencing participants’ natural behaviour, no feedback or additional instructions were given during the walking task. All participants completed the task in both clockwise and counterclockwise directions. Each participant completed at least six 360˚ turns in each direction. Before testing, an experimenter (YR or WY) provided the task instructions both verbally and through demonstration. Participants were then asked to familiarise with the environment and the task by going through the testing protocol a few times. Instruments Kinematic data were collected using a motion capture system with 19 cameras (100 Hz, Prime x 13, Optitrack, USA). Participants were fitted with 6 retro-reflective markers positioned on 3 anatomical landmarks of each foot (heel, lateral malleolus and head of the first metatarsus). Kinetic data were collected using 9 force plates (1.2 m x 1.2 m each, 1000 Hz, AMTI, USA), arranged in a square pattern, covering an area of ~ 13 m 2 . The experimental task was designed to maximise participants’ navigation of the space, while ensuring that all walking occurred on the force plates array (3x3). A video camera (25 Hz, HDR-CX405, Sony) was used to record the trials to allow the identification of turns affected by freezing of gait [ 26 ]. Data Analysis and Outcome Variables Video, kinematic and kinetic data relating to all turns were visually inspected and analysed semi-automatically. Data were processed using customised scripts and functions written in Matlab (R2023a, MathWorks, Natick, MA, USA). Kinematic and kinetic data were low pass filtered using a fourth order Butterworth filter with a cut-off frequency of 15 Hz ( 27 ). The filtered kinematic data were used to identify the time windows of the turns based on the physical position of the turn target within the motion capture reference system. This followed a two-step approach: the time between the stop and the beginning of the APA (defined as in 8 ) was estimated. If this time was shorter than 3 seconds, the trial was excluded from further analysis to avoid CoP waveforms being affected by the short transition (i.e. absence of quiet stance). If the time was longer than 3 seconds, the turn was deemed suitable for the analysis. A second time window was then extracted, from the moment the participant fully stopped with both feet on the visual target to the completion of the first step of the turn. Although this approach led to the exclusion of a significant number of turns (59%), it represents a conservative method to ensure data quality. Additionally, allowing participants to choose their initial turn direction and perform the task at a self-selected pace enhanced the generalisability of the findings to real-world scenarios. Moments and force components were used to calculate the CoP coordinates. The CoP trajectories were extracted based on the time windows described above. The reference system used to represent the CoP trajectory during the time window was rotated following the orientation of the base of support (BoS) and then adjusted depending on the leading limb and the turning direction, allowing for the comparison of the CoP waveforms (see 8 ). To reliably allow the identification of the onset of APAs, a threshold value was set for each turn window as three standard deviations above the baseline value during a 1-second quiet standing period (taken from the time window immediately preceding the turn, see above). The following landmarks were identified on the CoP trajectories for each time window [ 8 ]: i) APA Start: the initial point when the CoP trajectory exceeded the threshold value. ii) APA Peak: the first postero-lateral peak following the APA Start. iii) APA End: the time at which the CoP trajectory shifted from the mediolateral to the anteroposterior direction. APAs features and first step characteristics were extracted as described in Table 1 . Figure 2 provides a graphical summary of the CoP trajectory during the APAs, with key landmarks highlighted. Table 1 summarizes the outcome variables extracted in the study and provides a brief description of how each was estimated. AP = Anteroposterior; ML = Mediolateral; Total = linear distance calculated as \(\:\sqrt{{AP}^{2}+{ML}^{2}}\) ; BOS = Base of Support. Variable Description APA1 Duration Time between APA Peak and APA Start. APA1 Amplitude (AP, ML and Total) Spatial difference in CoP coordinates between APA Peak and APA Start. APA1 Velocity APA1 Amplitude Total divided by APA1 Duration. APA2 Duration Time between APA Peak and Foot Off Time. APA2 Amplitude (AP, ML and Total) Spatial difference in CoP coordinates between Foot Off and APA Peak. APA2 Velocity APA2 Amplitude Total divided by APA2 Duration Weight Shift Duration Time between APA Peak and APA End Weight Shift Amplitude (Total) Spatial difference in CoP coordinates between APA End and APA Peak Weight Shift Velocity Weight Shift Amplitude divided by Weight Shift Duration Foot Off Time First foot motion capture marker of the stepping foot (i.e. toe or heel) to exceed the threshold value. Time to Foot Off Percentage ratio of the weight shift phase duration to the total time until Foot Off. Foot Contact Last foot motion capture marker of the step leg (i.e. either toe or heel) to return under the threshold value Step Length Linear distance between the ankle marker positions of the stepping leg, calculated between Foot Off and Foot Contact. Step Velocity Step Length divided by Step Duration (Foot Contact – Foot Off). BOS Linear distance between the ankle markers. Spatiotemporal parameters of APAs (i.e. duration, amplitude and velocity) were measured for both APA1 (imbalance), APA2 (unloading) and total weight-shift along the mediolateral and anteroposterior components. The linear distance covered by the CoP during a given phase was calculated as the square root of the sum of the anteroposterior and mediolateral components. As the APAs amplitude APA1, APA2 and weight-shift are influenced by the BoS [ 5 ] these variables were normalised for the participants’ BoS. Additionally, CoP trajectories related to the weight-shift were time normalised (500 points) to allow waveform correlation analysis. The spatiotemporal characteristics of the first step were also extracted. During the analysis of the CoP trajectories, signals were visually inspected to identify possible features of APAs in turning that are not typical to APAs in gait initiation. Video recordings of the trial were used to identify the overall frequencies of turning strategies adopted by participants (i.e. which limb was leading in the context of the turn direction), regardless of whether they stopped or experienced freezing. Additionally, the recordings were used to identify turns that had to be discarded from the analysis due to experimenter’s interventions (e.g. supporting people to prevent falls) or freezing of gait. Specifically, freezing of gait was assessed through the annotation of video recordings by a panel (YR, WY, ZW) [ 26 ]. Turns that involved or were preceded by freezing (< 3 seconds) were excluded from the analysis, as were participants with fewer than three valid turns. Three randomly selected turns per participant were included in the final analysis. Statistical Analysis APAs, step characteristics and balance scores were summarised using the median and interquartile range. Nonparametric tests were used, where appropriate, due to the small sample size. Effect sizes were quantified using the r coefficient (see 28 ). Two-tailed Mann-Whitney U tests were conducted to compare APAs, step characteristics and balance scores, between the two groups, while two-tailed Wilcoxon signed-rank tests were used to compare APAs and first step characteristics in the PD group when turning was initiated with the most affected side versus the least affected side. Spearman’s rank correlation coefficients were calculated to describe the relationships between APAs (total displacement features) and first step characteristics in turning, and between people’s balance and adopted turning strategies. Time normalised weight-shift waveforms for each group were compared using the coefficients of multiple correlation (CMC, 29 ) to investigate intra-group variability. Statistical analysis was carried out using SPSS (v.28, IBM Corp, Armonk, NY, USA). A customised function written in Matlab was used to perform the CMC analysis. For all analyses, the level of significance was set to α = 0.05. Results Participants A total of 22 pwPD and 17 healthy older adults were included in the final analysis. Five participants (3 pwPD) were excluded due to technical issues during data collection, and sixteen (11 pwPD) were excluded because they did not have at least three trials suitable for APA analysis. Of 22 pwPD included, 7 self-identified as experiencing freezing of gait based on the first item of the NFOG-Q. Two of these experienced freezing during the testing session. Participant characteristics are summarized in Table 2 . Table 2 summarises the participants characteristics. pwPD = people with Parkinson’s; UPDRS – III = Unified Parkinson’s Disease Rating Scale-Part III; H&Y = Hoehn and Yahr Stage; SD = standard deviation; IQR = interquartile range; FOG = freezing of gait; NFOG = new freezing of gait questionnaire. Characteristics Healthy Older Adults People with PD Sex Female, n (%) 9F (53%) 10F (46%) Age years, mean ± SD 73.41 ± 8.02 68.96 ± 8.62 Height metres, mean ± SD 1.69 ± .12 1.70 ± .09 Body Mass kilograms, mean ± SD 74.84 ± 16.49 75.20 ± 16.94 MiniBEST score, median ± IQR 27.0 ± 3.0 22.0 ± 4.5 UPDRS-III score, mean ± SD - 31.68 ± 13.74 H&Y stage, median ± IQR - 2 ± 1 FOG pwPD and FOG, n (%) - 7 (32%) NFOG score, mean ± SD (only for pwPD and FOG) - 22.7 ± 4.46 (7 People) Characteristics of APAs in turning Descriptive data of the APAs and first step characteristics for the healthy older adults’ group are reported in Table 3 . The variability of APAs in turning was high as shown by the reported coefficients of variation and the CMC analysis (see Table 3 ). However, no features unique to APAs in turning were identified during visual inspections of CoP trajectories before turning. We observed that step length and velocity positively correlated with APA1 (p = .002, r = .627 and p < .001, r = 534, respectively), APA2 (p < .001, r = .529 and p = .006, r = .414, respectively), and weight-shift (p < .001, r = .574 and p = .002, r = .490, respectively). Table 3 summarises the study's main results. Data is reported as median ± interquartile range. BOS = base of support; m = metres; s = seconds; ms = milliseconds; cm = centimetres; CMC = coefficients of multiple correlation. Significant differences are highlighted in bold. Please note that APA1, APA2 and weight shift amplitudes reported in the table are normalised for the BOS. Outcome Variable Healthy Controls People with PD P value MiniBest 27.0 ± 3.0 22.0 ± 4.5 < .001 BOS (cm) 23.0 ± 6.0 24.0 ± 5.0 .769 APA1 Duration (ms) 127 ± 122 130 ± 61 .664 APA1 Amplitude AP (cm) 0.5 ± 1 0.5 ± .0 .232 APA1 Amplitude ML (cm) 0.7 ± 2.0 0.6 ± 1.0 .190 APA1 Amplitude Total (cm) 5.0 ± 10.0 5.0 ± 5.0 .181 APA1 Velocity (m/s) 0.10 ± .09 0.05 ± .05 < .001 APA2 Duration (ms) 73 ± 27 64 ± 56 .267 APA2 Amplitude AP (cm) 0.9 ± 2.0 0.6 ± 1.0 .008 APA2 Amplitude ML (cm) 0.4 ± .0 0.2 ± .0 .017 APA2 Amplitude Total (cm) 5.0 ± 5.0 2.5 ± 3.0 .002 APA2 Velocity (m/s) 0.27 ± .49 0.19 ± .30 .457 Weight Shift Duration (ms) 321 ± 216 328 ± 122 .944 Weight Shift Amplitude (cm) 44.0 ± 12.0 37.5 ± 9.0 .017 Weight Shift Velocity (m/s) 0.32 ± .15 0.27 ± .10 .077 Time to Foot Off (%) 25 ± 10 21 ± 15 .424 Step Length (cm) 16.0 ± 17.0 7.5 ± 6.0 .021 Step Velocity (m/s) 3.01 ± 2.64 1.51 ± 1.14 .039 CMC Coefficient 0.22 0.18 - Healthy older adults showed a clear preference for initiating a turn towards the right (~ 84% of turns). Furthermore, as participants could self-select both the turn direction and the initiating leg, we identified two possible strategies: i) enlarge the BoS by initiating the turn with the leg in the same direction of turn (here called ipsilateral initiation); ii) reducing the BoS by initiating the turn with the leg opposite of the direction of the turn (here called contralateral initiation). No associations were found between balance scores and the adopted turning strategies (p > .05). Frequencies of the different turning strategies are reported in Table 4 . Table 4 a summarises the frequency of turns for the Parkinson's group and the healthy control group, categorized by turning direction and stepping leg. Ipsilateral (CCW/L and CW/R) and contralateral (CCW/R and CW/L) initiations are here presented in detail. CCW = Counterclockwise turn; CW = Clockwise turn; L = Left stepping foot; R = Right stepping foot. CCW CW L R CCW/L CCW/R CCW R/L CW/L CW/R CW R/L Total Turns PwPD 68 252 140 181 40 28 100 152 320 Percentage 21.25 78.75 43.75 56.56 12.50 8.75 41.18 31.25 47.50 60.32 HC 39 207 118 128 27 12 91 116 246 Percentage 15.85 84.15 47.97 52.03 10.98 4.88 30.77 36.99 47.15 56.04 Table 4 b summarises the turning strategies of people with PD based on their most/least affected side (according to the UPDRS-III scores). R = Right; L = Left; M = Most Affected Side; L = Least Affected Side. Most Affected Side Participant Turn Direction M Turn Direction L Step M Step L Turn M / Step M Turn M/ Step L Turn L / Step M Turn L/ Step L Total Turns L PFOG07 5 3 7 1 5 0 2 1 8 L PFOG08 0 10 2 8 0 0 2 8 10 L PFOG16 11 1 10 2 10 1 0 1 12 R PFOG17 13 0 10 3 10 3 0 0 13 L PFOG18 5 4 1 8 0 5 1 3 9 L PFOG20 0 9 2 7 0 0 2 7 9 L PFOG22 0 15 2 13 0 0 2 13 15 L PNFOG04 7 9 4 12 1 6 3 6 16 R PNFOG05 14 9 15 9 12 1 1 8 23 L PNFOG06 1 16 8 9 1 0 7 9 17 R PNFOG07 6 6 3 9 1 5 2 4 12 R PNFOG08 12 1 5 8 5 7 0 1 13 R PNFOG09 8 5 9 4 6 2 3 2 13 L PNFOG10 8 9 6 11 4 4 2 7 17 L PNFOG11 0 14 0 14 0 0 0 14 14 R PNFOG13 11 2 8 5 8 3 0 2 13 L PNFOG14 0 16 15 1 0 0 15 1 16 R PNFOG17 17 0 8 9 8 9 0 0 17 L PNFOG20 5 10 2 13 0 5 2 8 15 R PNFOG21 12 3 7 8 6 6 1 2 15 Percentage 48.73646 51.26354 44.60432 55.39568 27.89855 20.65217 16.30435 35.14493 13.85 Table 4 HERE (Because of the layout Table 4 is at the end of the document) Comparisons between HC and PD Differences between pwPD and healthy older adults were observed for both APAs and first step characteristics. Specifically, compared to healthy older people, pwPD showed smaller APA2 values for anteroposterior, mediolateral and total displacement (p = .008 r = .42; p = .017 r = .38; p = .002, r = .50, respectively) as well as reduced total weight-shifts (p = .017, r = .39). PwPD showed slower APA1 (p < .001, r = .94) but similar velocities of APA2 (p = .457, r = .12) and weight-shift (p = .077, r = .29) in comparison to healthy older people. Step length was shorter in pwPD compared to healthy older people (p = .021, r = .37); further steps were slower in PwPD (p = .039, r = .33). PwPD showed similar variability in APAs compared to healthy controls (see Table 3 ). In pwPD, we observed a lack of significant correlations between step length and velocity with APA1 (p > .05, r = .211 and p > .05, r = .173, respectively) and APA2 (p > .05, r = .213 and p > .05, r = .218, respectively). Correlations were statistically similar between HC and pwPD for weight-shift (p < .001, r = .500 and p<, r = .554, respectively). No other notable differences were observed. Similarly to healthy older adults, pwPD showed a clear preference for initiating a turn towards the right (~ 79% of turns; see Table 4 ). A significant association was found between balance scores and the frequency of contralateral initiation of turns (p = .016, r = .533). Comparison of APAs between turns towards most/least affected side People with PD were overall more likely to initiate a turn using strategies that increased their BoS (ipsilateral initiation: ~63% of turns) compared to strategies that reduced it (contralateral initiation: ~37% of turns, see Table 4 ). However, pwPD with poorer balance (miniBEST < 20) used contralateral initiations less often (13% of turns) than pwPD who had better balance (miniBEST ≥ 20, 38% of turns). There were no clear preferences in turning direction dictated by the most/least affected side. Since most participants had a clear preference for a specific turning direction, only 8 participants with PD were included in the comparison of APAs and step characteristics between the most and least affected side. No significant differences were observed in either APAs or step characteristics between turns towards the most versus least affected side. Discussion The current study characterised APAs prior to turning in healthy older adults and pwPD. Our findings show that APAs in turning share several features with those preceding forward gait initiation [ 4 , 7 , 8 ], albeit with preparatory adjustments primarily occurring along the mediolateral direction. Additionally, our results highlight key differences between healthy older adults and pwPD in both APA features (i.e. amplitude but not duration) and first-step characteristics (i.e. step length and velocity). Interestingly, significant associations between APA features and step execution were found only in healthy older adults, suggesting that PD may disrupt the relation between task preparation and execution during turning. APAs in turning: features in uncontrived tasks APAs prior to voluntary turning follow a similar fundamental pattern to those observed in forward gait initiation [ 4 , 7 ], reflecting the postural preparation required to displace the body during bipedal movements. Before turning, the CoP shifts backward and laterally under the stepping foot, transferring body weight onto the standing limb. This shift ensures a safe foot-off by reducing the distance between the centre of mass and the medial margin of the BoS. However, compared to forward gait initiation [ 7 , 8 ], and in line with our hypothesis, our data show that APA1 amplitude tends to be smaller and shorter during turning, aligning more closely with APA1 reported in lateral stepping [ 18 ]. We attribute this difference to the fact that, while turning on the spot does not require the anterior acceleration needed in forward gait initiation, it still demands a small and precise forward shift to avoid instability. APA2 and weight-shift characteristics did not show distinguishable differences from forward gait initiation, likely because these components are primarily related to the effective transfer of body weight onto the standing leg. However, we observed greater variability in these components during turning, as indicated by higher coefficients of variation and a much lower CMC. For example, in forward gait initiation, weight shift typically exhibits very low inter-personal variability (CMC = 0.90) [ 8 ], while in the current study, we found substantial variability (CMC = 0.22). Although some of this difference could be attributed to the more controlled nature of the task performed in Russo & Vannozzi's study and the higher number of trials, we believe that the increased variability observed in this study is more likely produced by the greater complexity of turning. In fact, turning involves movements along the transverse plane and allows for more strategies (i.e., turn direction and stepping leg) compared to forward gait initiation, which is limited to selecting the stepping leg. APAs in turning: effects of Parkinson’s Disease In line with our initial hypothesis, individuals with PD demonstrated impoverished APAs compared to healthy older adults. Specifically, pwPD exhibited reduced APA2 amplitude and smaller weight-shift components, as well as slower execution of APA1. These findings are consistent with previous research on forward gait initiation, where impaired APAs in PD were linked to difficulties in task execution and balance control [ 5 , 10 ]. The smaller APAs amplitudes observed in pwPD (APA2 and weight-shift) and the slower APA1 suggest a reduced capacity to adequately prepare for the dynamic demands of turning, potentially increasing the risk of falls during everyday tasks involving changes in body orientation due to altered weight shifts [ 30 ]. Furthermore, this may be indicative of deficits in both motor and postural control, suggesting an altered ability to precisely adjust the spatiotemporal characteristics of APAs to align with the motor program for the turning step, which may further compromise stability during turning. Taken together these results may explain why pwPD were overall more likely to adopt strategies that increased their BoS when initiating turning (~ 63% of turns), compared to strategies that reduced it (~ 37%). This preference for stability-enhancing strategies may reflect an adaptive response to their postural control impairments, as expanding the BoS may provide greater stability during dynamic movements such as turning. Interestingly, while pwPD exhibited shorter and slower steps during turning initiation, no significant differences were found between the two groups for foot-off percentage or the duration of any of the APA components. Although this lack of difference may be partly confounded by our inclusion criteria (e.g., balance abilities) and the relatively small sample size (when taking into account the overall variability observed), we speculate that the temporal components of APAs in turning might be less impaired in the early stages of PD, especially during uncontrived turning, where preparatory mechanisms may be more preserved compared to spatial ones. Turning Side and APA Characteristics Our analysis of turns towards the most versus least affected side in pwPD did not reveal significant differences in APAs or step characteristics. Furthermore, pwPD overall preferred to use turning strategies that prioritised the increase of the BoS rather than showing a preference based on most/least affected side, which may indicate that, different to forward gait initiation, severity asymmetries only in turning play a minor role during turning [ 31 ]. Although we admittedly only had a relatively small sample size (8 pwPD), these findings corroborate results recently published by Seuthe and co-workers [ 31 ] who identified asymmetries in gait but not turning in people with mild-to-moderate PD. A possible explanation is that asymmetry may be apparent in relatively simple task (e.g. gait initiation), but it may be masked/no longer apparent in more complex tasks where other aspects (e.g. turning strategy) may play a more pivotal role. Turning requires a fine coordination between body segments, and compared to forward gait, it poses greater challenges for sensory integration [ 32 ] and it requires greater cognitive demands [ 33 ]. Furthermore, these factors are likely to be further exacerbated in less prescribed/contrived adaptive gait tasks, such as that used in the current study. Therefore, while this more naturalistic behaviour could serve to mask subtle differences, the current data suggests that these differences are not of a sufficient magnitude to be clinically important. Potential implications for Rehabilitation and Clinical Practice Research indicates that turning is more vulnerable to balance and functional impairments than forward walking due to its complex demands [ 34 ]. In fact, during turning, pwPD are more likely to experience freezing of gait or falls [ 15 , 21 ]. Impairments in APAs are considered a major contributor to difficulties with gait initiation in pwPD [ 14 ], and dysfunctional APAs have been proposed as a possible cause of freezing of gait [ 35 ]. However, it is often challenging to observe differences in APAs during gait initiation in participants who are ON-medication, as dopamine tends to improve APAs [ 5 ] especially in people with moderate PD and without FOG [ 16 ], potentially masking PD-related impairments in balance control. However, despite our relatively small sample consisting of individuals with mild-to-moderate PD tested ON medication, we were able to detect significant differences both in the preparatory phase of turning and in the first step. Although more work is necessary to improve the generalisability of our results, the sensitivity of turn initiation in detecting subtle changes in postural control makes it a promising candidate for its inclusion in clinical assessments. While turning is generally associated with a narrower BoS in pwPD [ 36 ], we did not observe differences in self-selected BOS prior to turns in this uncontrived task. However, our results highlighted a significant association between balance ability and the adopted turning strategy in pwPD, with higher balance scores linked to more frequent use of contralateral turn initiation, implying a reduced BoS. Interestingly, this relationship was not observed in healthy older adults. Reducing the BoS when initiating a turn may represent a more challenging strategy as there is potential instability at the end of the first step, due to momentum in the direction of the turn that could push the centre of mass beyond the margins of the BoS. We believe that for individuals with good balance, contralateral initiation does not pose a significant threat. As such, we would not expect to observe any relationship between balance ability and turn-initiation strategy in healthy older adults. In contrast, pwPD, who demonstrated poorer overall balance, may adopt the ipsilateral initiation strategy as an active avoidance mechanism to reduce postural instability during turning. Overall, pwPD with poorer balance (miniBEST < 20) initiated turns using a contralateral strategy 13% of times, while those with better balance (miniBEST ≥ 20) did so 38% of times. This suggests that people still tend to adopt a strategy, when under no specific time-pressure, that poses a non-negligible risk to balance. These findings are reminiscent of observations of behavioural risk-taking in older adults [ 37 , 38 ], and the use of cross-stepping in nursing homes residents [ 39 ]. In these studies, participants either selected higher risks tasks [ 37 , 38 ] or unnecessarily opted for strategies (i.e. cross-stepping) which narrow the BoS, thus posing an increased challenge for the balance system. In the context of this study, cross-stepping may be viewed as an extreme example of contralateral turn initiation. As such, this type of behaviour could be maladaptive and enhance fall risk. Furthermore, as BoS reduction during turning is thought to be a key factor in falls [ 36 ], this suggests a possible rehabilitation strategy: encouraging pwPD who have high instability to avoid transitioning directly from walking to turning, but instead to break the task into two distinct steps. Recent evidence suggests that especially pwPD who experience freezing could benefit by incorporating pauses/breaks between tasks or during a freeze to regain control over their balance [ 40 ]. Limitations and future directions This study has three main limitations. i) Uncontrived turning task resulting in a significant loss of data suitable for APA analysis (e.g., absence of pauses or lack of turns in a given direction among pwPD). However, we believe this is also a key strength of the study, as it provides valuable insights into turning initiation in a naturalistic context, making the findings more applicable to real-life situations. ii) Small sample size for comparing turns between the most and least affected sides in PD. The small sample size limited our ability to fully assess side-specific impairments in turning initiation. Future research with larger samples is needed to better understand how such asymmetries impact turning initiation in pwPD. Additionally, although participants were assessed in their ON-medication state, the specific effects of medication on APAs characteristics during turning were not explored, which represents an important area for future investigation. iii) Exclusion of participants with poor balance. Since individuals with poor balance, who are typically in the later stages of PD, were excluded from this study, the generalisability of these findings is limited. Including participants with more advanced balance impairments in future research would provide a more comprehensive understanding of turning difficulties across the full spectrum of PD severity. Conclusion In summary, APAs prior to turning share several similarities with APAs prior to gait initiation. When compared to healthy older adults, people with PD exhibit significant impairments in APAs execution during turning, including reduced amplitude and slower execution, which may contribute to the high incidence of falls during turning in this population. Our findings underscore the need for targeted interventions to address these specific motor deficits and suggest that strategies promoting weight-shifting and a stable base of support may aid in mitigating fall risk. Future research should continue to explore the interplay between motor asymmetry, medication effects, and turning performance to further refine clinical approaches to balance rehabilitation in PD. Declarations Competing interests The authors declare no competing interests. Funding This work was funded by Parkinson’s UK (G-2007) and was supported by the National Institute for Health and Care Research Exeter Biomedical Research Centre. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. Author Contribution Conception and design - YR & WY Acquisition of data - YR, PL, JY, ZW and WY Data curation, formal analysis and visualisation - YR Writing original draft - YR & WYWriting review & editing - All the authorsFinal approval of the completed article - All the authorsFunding acquisition - WY, AN, MW, MN, EK, SL Acknowledgement We thank the participants, the people who accompanied them in the laboratory, the members of Parkinson’s UK branches who have supported our recruitment as well as our Project Advisory Group for their contributions to study conception, design, interpretation of results and dissemination. Data Availability The data that support the findings of this study are available from the corresponding author upon reasonable request. Video recordings cannot be made available in line with privacy regulations. References Jacobs, J. V. & Horak, F. B. External postural perturbations induce multiple anticipatory postural adjustments when subjects cannot pre-select their stepping foot. Exp Brain Res 179 , 29–42 (2007). Hiraoka, K., Matuo, Y., Iwata, A., Onishi, T. & Abe, K. The effects of external cues on ankle control during gait initiation in Parkinson’s disease. Parkinsonism Relat Disord 12 , 97–102 (2006). Rosin, R., Topka, H. & Dichgans, J. Gait initiation in Parkinson’s disease. Movement Disorders 12 , 682–690 (1997). Crenna, P. & Frigo, C. A MOTOR PROGRAMME FOR THE INITIATION OF FORWARD-ORIENTED MOVEMENTS IN HUMANS . Journal of Physiology vol. 437 (1991). Rocchi, L. et al. Step initiation in Parkinson’s disease: Influence of initial stance conditions. 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L., Schieppati, M., Crisafulli, O. & Do, M. C. The neuro-mechanical processes that underlie goal-directed medio-lateral APA during gait initiation. Front Hum Neurosci 10 , (2016). Rum, L., Russo, Y., Vannozzi, G. & Macaluso, A. “Posture first”: Interaction between posture and locomotion in people with low back pain during unexpectedly cued modification of gait initiation motor command. Hum Mov Sci 89 , (2023). Tajali, S. et al. Effects of external perturbations on anticipatory and compensatory postural adjustments in patients with multiple sclerosis and a fall history. Int J MS Care 20 , 164–172 (2018). Burleigh-Jacobs, A., Horak, F. B., Nutt, J. G. & Obeso, J. A. Step initiation in Parkinson’s disease: Influence of levodopa and external sensory triggers. Movement Disorders 12 , 206–215 (1997). Bloem, B. R., Hausdorff, J. M., Visser, J. E. & Giladi, N. Falls and freezing of Gait in Parkinson’s disease: A review of two interconnected, episodic phenomena. 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How to Annotate Freezing of Gait from Video: A Standardized Method Using Open-Source Software. J Parkinsons Dis 9 , 821–824 (2019). Russo, Y., Berchicci, M., Di Russo, F. & Vannozzi, G. How do different movement references influence ERP related to gait initiation? A comparative methods’ assessment. J Neurosci Methods 311 , 95–101 (2019). Rosenthal, R. Parametric measures of effect size. in The handbook of research synthesis (eds. Cooper, H. & Hedges, L.) 231–244 (Russel Sage Foundation, 1994). Kadaba, M. P. et al. Repeatability of kinematic, kinetic, and electromyographic data in normal adult gait. Journal of Orthopaedic Research 7 , 849–860 (1989). Weaver, T. B., Robinovitch, S. N., Laing, A. C. & Yang, Y. Falls and Parkinson’s Disease: Evidence from Video Recordings of Actual Fall Events. J Am Geriatr Soc 64 , 96–101 (2016). Seuthe, J. et al. Gait asymmetry and symptom laterality in Parkinson’s disease: two of a kind? J Neurol 271 , 4373–4382 (2024). Bohnen, N. I., Kanel, P., van Emde Boas, M., Roytman, S. & Kerber, K. A. Vestibular Sensory Conflict During Postural Control, Freezing of Gait, and Falls in Parkinson’s Disease. Movement Disorders 37 , 2257–2262 (2022). Belluscio, V., Stuart, S., Bergamini, E., Vannozzi, G. & Mancini, M. The Association between Prefrontal Cortex Activity and Turning Behavior in People with and without Freezing of Gait. Neuroscience 416 , 168–176 (2019). Earhart, G. M. Dynamic control of posture across locomotor tasks. Movement Disorders vol. 28 1501–1508 Preprint at https://doi.org/10.1002/mds.25592 (2013). Nutt, J. G. et al. Freezing of Gait: Moving Forward on a Mysterious Clinical Phenomenon . Lancet Neurol vol. 10 www.thelancet.com/neurology (2011). Mellone, S., Mancini, M., King, L. A., Horak, F. B. & Chiari, L. The quality of turning in Parkinson’s disease: A compensatory strategy to prevent postural instability? J Neuroeng Rehabil 13 , (2016). Kluft, N., Bruijn, S. M., Weijer, R. H. A., Van Dieën, J. H. & Pijnappels, M. On the validity and consistency of misjudgment of stepping ability in young and older adults. PLoS One 12 , (2017). Butler, A. A., Lord, S. R., Taylor, J. L. & Fitzpatrick, R. C. Ability Versus Hazard: Risk-Taking and Falls in Older People. Journals of Gerontology - Series A Biological Sciences and Medical Sciences 70 , 628–634 (2015). Robinovitch, S. N. et al. Video capture of the circumstances of falls in elderly people residing in long-term care: An observational study. The Lancet 381 , 47–54 (2013). Russo, Y. et al. Russo, Y., et al. "Can A Single-Session Of Weight-Shift Training Support People With Parkinson’s Step From A Freeze? in Movement Disorders 107–108 (2023). Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6172807","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":427182842,"identity":"c7d5356f-963c-4e18-a8d8-b494b3bfd283","order_by":0,"name":"Yuri Russo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIiWNgGAWjYBADOWQOM1FajIGYsYEkLYkNRGsxOMD7TPLHH5v0fonk4w8+7mGQ52/gMTbAr4XdTJq3LS13Zs+xxMYZzxgMZxzgMU7Ar4WNTZqx4XDuhuM9hs08BxgYNzDwGB8gpAXosMPp9of5Pzb/OcBgT5QWCR62wwkG7D2MzQwHGBJBWvA6TPIwG7M10C+GM84cM5zZc0AiecZhtmK83uc73sZ4Exhi8vwzkh98+HHAxra/vXmzBD4tCodR+RKEI1K+gYCCUTAKRsEoGAUMAOj/RGNZNkp0AAAAAElFTkSuQmCC","orcid":"","institution":"University of Exeter","correspondingAuthor":true,"prefix":"","firstName":"Yuri","middleName":"","lastName":"Russo","suffix":""},{"id":427182843,"identity":"d43df04c-5c1d-4921-8af0-112b6540c1da","order_by":1,"name":"Phaedra Leveridge","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"Phaedra","middleName":"","lastName":"Leveridge","suffix":""},{"id":427182844,"identity":"0416d52b-f658-4a78-9646-d4e26c1fc1f6","order_by":2,"name":"Jiaxi Ye","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"Jiaxi","middleName":"","lastName":"Ye","suffix":""},{"id":427182845,"identity":"4d080f2e-9617-401d-9979-323bbe532b74","order_by":3,"name":"Zijing Wang","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"Zijing","middleName":"","lastName":"Wang","suffix":""},{"id":427182846,"identity":"e7f41b31-fb59-4e6e-89d2-27fe526396e1","order_by":4,"name":"Alice Nieuwboer","email":"","orcid":"","institution":"Katholieke Universiteit Leuven","correspondingAuthor":false,"prefix":"","firstName":"Alice","middleName":"","lastName":"Nieuwboer","suffix":""},{"id":427182847,"identity":"fbf2123e-8dfa-4820-acbc-8d83676f9b06","order_by":5,"name":"Sarah E Lamb","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"Sarah","middleName":"E","lastName":"Lamb","suffix":""},{"id":427182848,"identity":"ddc255bf-acbb-4029-a94d-e5604173a267","order_by":6,"name":"Elmar Kal","email":"","orcid":"","institution":"Brunel University of London","correspondingAuthor":false,"prefix":"","firstName":"Elmar","middleName":"","lastName":"Kal","suffix":""},{"id":427182849,"identity":"82e2c299-f1b2-40d7-b1d7-875dfad36f80","order_by":7,"name":"Meriel Norris","email":"","orcid":"","institution":"Brunel University of London","correspondingAuthor":false,"prefix":"","firstName":"Meriel","middleName":"","lastName":"Norris","suffix":""},{"id":427182850,"identity":"f54220dd-1cab-4121-ad4a-b04b2f3c646c","order_by":8,"name":"Mark Wilson","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"Mark","middleName":"","lastName":"Wilson","suffix":""},{"id":427182851,"identity":"78e13c32-b2ff-4253-90c5-239a03c0f2d8","order_by":9,"name":"William R Young","email":"","orcid":"","institution":"University of Exeter","correspondingAuthor":false,"prefix":"","firstName":"William","middleName":"R","lastName":"Young","suffix":""}],"badges":[],"createdAt":"2025-03-06 18:08:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6172807/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6172807/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-33425-5","type":"published","date":"2025-12-22T15:57:46+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":78323359,"identity":"f4eca8a6-0c5b-4d5a-b30b-8e0d917fd174","added_by":"auto","created_at":"2025-03-12 05:40:48","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":298522,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eGraphical representation of the walking task. Each grey square represents the position of a force plate. The blue circles indicate the locations of the cones, while the black and yellow circle marks the target where participants stopped and performed a 360˚ turn. The green circular arrows represent the points where participants executed the turns. The black lines illustrate the relative positions of the targets within the instrumented floor, as well as the dimensions of the instrumented floor.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6172807/v1/7d68de9082b7e66b2ff5b51b.png"},{"id":78323362,"identity":"ddc07f1a-2b20-4fbb-9ca1-bf11d33dcf97","added_by":"auto","created_at":"2025-03-12 05:40:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":284143,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eillustrates the CoP trajectory during the initiation of a counter-clockwise turn from a randomly selected healthy participant. The CoP trajectory is shown during a left-foot-initiated turn (stepping leg). The light-yellow shapes represent the feet as identified by motion capture markers, while the dark blue line represents the CoP trajectory over time. Black circles highlight the landmarks used to identify and segment the APA phases.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6172807/v1/23d88e04c951aa9496727a55.png"},{"id":99172320,"identity":"986af8fb-0514-4c7a-a746-cb314334fc7e","added_by":"auto","created_at":"2025-12-29 16:07:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1957613,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6172807/v1/68215e16-90d6-4fd1-924e-3a55d239b503.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterising Anticipatory Postural Adjustments in Turning: A Comparison Between Healthy Older Adults and People with Parkinson’s Disease","fulltext":[{"header":"Introduction","content":"\u003cp\u003eVoluntary stepping movements are often preceded by Anticipatory Postural Adjustments (APAs). These preparatory adjustments rely on specific motor programmes generated by the central nervous system before the intended movement [\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e] to promote postural stability during the initiated step [\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e]. APAs are modulated according to environmental demands and conditions (e.g. time constraints, emotional state, base of support [\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e]). In forward gait initiation, APAs shift the centre of mass forwards and towards the standing limb i.e. unloading the stepping leg and preparing the body to accelerate forward [\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e]. APAs can be divided into two phases: imbalance and unloading [\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e]. The first promotes unloading of the stepping leg while accelerating the centre of mass forward, and the second represents the weight-shift associated with preparation for mono-pedal stance and heel-off.\u003c/p\u003e \u003cp\u003eAPAs preceding gait initiation are shown to be stable in healthy people [\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e] and are not significantly influenced by healthy ageing [\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e]. However, APAs are often studied in clinical contexts as they significantly influence first-step characteristics and walking performance [\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e]. Established evidence show that APAs are impaired in clinical populations [\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e], particularly in people with Parkinson\u0026rsquo;s (pwPD), where defective APAs contribute to difficulties with gait initiation [\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e]. In pwPD, falls often occur during attempted postural transitions such as gait initiation and turning [\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e]), when effective APAs are critical to successful and safe step initiation. Despite their potential clinical relevance [\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e], however, our current understanding of APAs primarily stems from studies on forward step/gait initiation, while non-linear postural transitions (e.g., lateral stepping, initiation of turning) have received little attention [\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e]. This is surprising given that many tasks in daily life involve turning while stepping [\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e] and that pwPD find it difficult to attempt turning tasks, even in early stages of the disease [\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e]. In addition, turning behaviour has been shown to be more abnormal in PwPD with freezing of gait [\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e].\u003c/p\u003e \u003cp\u003eCompared to forward gait initiation, turning is more complex as it requires simultaneous translation and re-orientation of several body segments, as well as posing challenges of postural control. It is therefore more difficult to study given the limitations of conventional biomechanical/clinical laboratories which are often optimised for gait analysis. By using VSimulators laboratory (VSimulators Exeter), we were able to largely overcome these limitations by designing a complex walking task that broadly resembles common real-world demands without sacrificing the use of gold-standard technology (i.e. motion capture and force plates).\u003c/p\u003e \u003cp\u003eOur research aimed to: i) characterise APAs and properties of the first step during turning in healthy older adults; ii) compare these to pwPD; iii) explore whether there are asymmetries in APAs in pwPD when turning towards their most versus least affected side. We hypothesised that: i) APAs in turning would manifest primarily in the mediolateral direction, with small APAs in the anteroposterior direction; ii) similarly to that observed during forward gait initiation, pwPD would show longer and smaller APAs compared to healthy older adults; iii) we did not have a specific hypothesis regarding potential asymmetries in APAs between the most and least affected sides in PwPD.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design\u003c/h2\u003e \u003cp\u003eThis cross-sectional study characterised APAs and first-step characteristics in turning and compared these outcomes between healthy older adults and pwPD. All participants were tested at the VSimulators laboratory (VSimulators Exeter), University of Exeter, between March 2022 and October 2022. All participants with PD were tested while in their ON-medication state (~\u0026thinsp;60 minutes after taking their regular dopaminergic medication). If necessary, participants were allowed to re-administer their medication to ensure they remained in their ON state throughout the testing.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eParticipants\u003c/h3\u003e\n\u003cp\u003eThirty-six pwPD and twenty-four older healthy adults were recruited through the Parkinson\u0026rsquo;s UK research network and the local community. Participants were eligible if they: i) were over 55 years old; ii) were able to walk unsupported for at least one minute. An additional inclusion criterion for the PD group was an existing diagnosis of idiopathic PD (UK Brain Bank Criteria). Exclusion criteria for all participants were: i) moderate cognitive impairment (Montreal Cognitive Assessment, MOCA, score\u0026thinsp;\u0026lt;\u0026thinsp;21 [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e]); ii) impaired normal or corrected-to-normal vision (Snellen Visual Acuity\u0026thinsp;\u0026lt;\u0026thinsp;12/18); and iii) any injury or disorder (other than PD) that might affect balance or walking. pwPD were asked to answer the first question of the New Freezing of Gait Questionnaire (NFOG-Q, [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e]) to self-identify whether they experience freezing. All participants provided written informed consent prior to participating in the study. The study was approved by the local institutional review board of the University of Exeter (21-12-08-B- 02, Department of Public Health \u0026amp; Sport Sciences).\u003c/p\u003e\n\u003ch3\u003eProcedure\u003c/h3\u003e\n\u003cp\u003eAfter providing written informed consent, participants with PD were assessed by a trained examiner (YR or WY) using the Mini-BESTest [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e] and the Motor Section (Part III) of the MDS-UPDRS which consists of 23 items evaluating bradykinesia, rigidity, tremor, posture and gait [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e]. They then underwent a walking test, designed to capture full body motion during turning and other elements of gait. The walking task was arranged in a square pattern with an external width/length of 3.6m x 3.6m. At regular intervals on each side of the square, a visual target of 15cm diameter was taped to the floor (see Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The target was black and yellow and had a high visual contrast with the floor (light grey). Following an initial standing period, participants were instructed to walk forward and stop on the visual target. They were asked to pause for a few seconds, before performing a full 360˚ turn towards a self-selected direction (i.e. clockwise or counterclockwise) at a self-selected speed. On completing the turn, participants were asked to stop for a couple of seconds before walking through two cones (positioned\u0026thinsp;~\u0026thinsp;.2m and ~\u0026thinsp;1 m from the outer lateral perimeter of the walkway and ~\u0026thinsp;1.4m from the outer perimeter in the direction of the walking, to guide the navigation of the space), perform a 90˚turn, and continue walking until reaching the next visual target. To have uncontrived turning and avoid influencing participants\u0026rsquo; natural behaviour, no feedback or additional instructions were given during the walking task. All participants completed the task in both clockwise and counterclockwise directions. Each participant completed at least six 360˚ turns in each direction. Before testing, an experimenter (YR or WY) provided the task instructions both verbally and through demonstration. Participants were then asked to familiarise with the environment and the task by going through the testing protocol a few times.\u003c/p\u003e\n\u003ch3\u003eInstruments\u003c/h3\u003e\n\u003cp\u003eKinematic data were collected using a motion capture system with 19 cameras (100 Hz, Prime\u003csup\u003ex\u003c/sup\u003e 13, Optitrack, USA). Participants were fitted with 6 retro-reflective markers positioned on 3 anatomical landmarks of each foot (heel, lateral malleolus and head of the first metatarsus). Kinetic data were collected using 9 force plates (1.2 m x 1.2 m each, 1000 Hz, AMTI, USA), arranged in a square pattern, covering an area of ~\u0026thinsp;13 m\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. The experimental task was designed to maximise participants\u0026rsquo; navigation of the space, while ensuring that all walking occurred on the force plates array (3x3). A video camera (25 Hz, HDR-CX405, Sony) was used to record the trials to allow the identification of turns affected by freezing of gait [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e].\u003c/p\u003e\n\u003ch3\u003eData Analysis and Outcome Variables\u003c/h3\u003e\n\u003cp\u003eVideo, kinematic and kinetic data relating to all turns were visually inspected and analysed semi-automatically. Data were processed using customised scripts and functions written in Matlab (R2023a, MathWorks, Natick, MA, USA). Kinematic and kinetic data were low pass filtered using a fourth order Butterworth filter with a cut-off frequency of 15 Hz (\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e). The filtered kinematic data were used to identify the time windows of the turns based on the physical position of the turn target within the motion capture reference system. This followed a two-step approach:\u003c/p\u003e\n\u003col style=\"list-style-type: lower-roman;\"\u003e\n \u003cli\u003ethe time between the stop and the beginning of the APA (defined as in \u003csup\u003e8\u003c/sup\u003e) was estimated. If this time was shorter than 3 seconds, the trial was excluded from further analysis to avoid CoP waveforms being affected by the short transition (i.e. absence of quiet stance).\u003c/li\u003e\n \u003cli\u003e\u0026nbsp;If the time was longer than 3 seconds, the turn was deemed suitable for the analysis. A second time window was then extracted, from the moment the participant fully stopped with both feet on the visual target to the completion of the first step of the turn.\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eAlthough this approach led to the exclusion of a significant number of turns (59%), it represents a conservative method to ensure data quality. Additionally, allowing participants to choose their initial turn direction and perform the task at a self-selected pace enhanced the generalisability of the findings to real-world scenarios.\u003c/p\u003e\n\u003cp\u003eMoments and force components were used to calculate the CoP coordinates. The CoP trajectories were extracted based on the time windows described above. The reference system used to represent the CoP trajectory during the time window was rotated following the orientation of the base of support (BoS) and then adjusted depending on the leading limb and the turning direction, allowing for the comparison of the CoP waveforms (see \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e). To reliably allow the identification of the onset of APAs, a threshold value was set for each turn window as three standard deviations above the baseline value during a 1-second quiet standing period (taken from the time window immediately preceding the turn, see above).\u003c/p\u003e\n\u003cp\u003eThe following landmarks were identified on the CoP trajectories for each time window [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e]: i) APA Start: the initial point when the CoP trajectory exceeded the threshold value. ii) APA Peak: the first postero-lateral peak following the APA Start. iii) APA End: the time at which the CoP trajectory shifted from the mediolateral to the anteroposterior direction. APAs features and first step characteristics were extracted as described in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e provides a graphical summary of the CoP trajectory during the APAs, with key landmarks highlighted.\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003esummarizes the outcome variables extracted in the study and provides a brief description of how each was estimated. AP\u0026thinsp;=\u0026thinsp;Anteroposterior; ML\u0026thinsp;=\u0026thinsp;Mediolateral; Total\u0026thinsp;=\u0026thinsp;linear distance calculated as \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\sqrt{{AP}^{2}+{ML}^{2}}\\)\u003c/span\u003e\u003c/span\u003e ; BOS\u0026thinsp;=\u0026thinsp;Base of Support.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDescription\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA1 Duration\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTime between APA Peak and APA Start.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA1 Amplitude\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(AP, ML and Total)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpatial difference in CoP coordinates between APA Peak and APA Start.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA1 Velocity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAPA1 Amplitude Total divided by APA1 Duration.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA2 Duration\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTime between APA Peak and Foot Off Time.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA2 Amplitude\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(AP, ML and Total)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpatial difference in CoP coordinates between Foot Off and APA Peak.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAPA2 Velocity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAPA2 Amplitude Total divided by APA2 Duration\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight Shift Duration\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTime between APA Peak and APA End\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight Shift Amplitude\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(Total)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpatial difference in CoP coordinates between APA End and APA Peak\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeight Shift Velocity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWeight Shift Amplitude divided by Weight Shift Duration\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eFoot Off Time\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFirst foot motion capture marker of the stepping foot (i.e. toe or heel) to exceed the threshold value.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime to Foot Off\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePercentage ratio of the weight shift phase duration to the total time until Foot Off.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eFoot Contact\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLast foot motion capture marker of the step leg (i.e. either toe or heel) to return under the threshold value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eStep Length\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLinear distance between the ankle marker positions of the stepping leg, calculated between Foot Off and Foot Contact.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eStep Velocity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStep Length divided by Step Duration (Foot Contact \u0026ndash; Foot Off).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eBOS\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLinear distance between the ankle markers.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eSpatiotemporal parameters of APAs (i.e. duration, amplitude and velocity) were measured for both APA1 (imbalance), APA2 (unloading) and total weight-shift along the mediolateral and anteroposterior components. The linear distance covered by the CoP during a given phase was calculated as the square root of the sum of the anteroposterior and mediolateral components. As the APAs amplitude APA1, APA2 and weight-shift are influenced by the BoS [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e] these variables were normalised for the participants\u0026rsquo; BoS.\u003c/p\u003e\n\u003cp\u003eAdditionally, CoP trajectories related to the weight-shift were time normalised (500 points) to allow waveform correlation analysis. The spatiotemporal characteristics of the first step were also extracted. During the analysis of the CoP trajectories, signals were visually inspected to identify possible features of APAs in turning that are not typical to APAs in gait initiation.\u003c/p\u003e\n\u003cp\u003eVideo recordings of the trial were used to identify the overall frequencies of turning strategies adopted by participants (i.e. which limb was leading in the context of the turn direction), regardless of whether they stopped or experienced freezing. Additionally, the recordings were used to identify turns that had to be discarded from the analysis due to experimenter\u0026rsquo;s interventions (e.g. supporting people to prevent falls) or freezing of gait. Specifically, freezing of gait was assessed through the annotation of video recordings by a panel (YR, WY, ZW) [\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e]. Turns that involved or were preceded by freezing (\u0026lt;\u0026thinsp;3 seconds) were excluded from the analysis, as were participants with fewer than three valid turns. Three randomly selected turns per participant were included in the final analysis.\u003c/p\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical Analysis\u003c/h2\u003e\n \u003cp\u003eAPAs, step characteristics and balance scores were summarised using the median and interquartile range. Nonparametric tests were used, where appropriate, due to the small sample size. Effect sizes were quantified using the r coefficient (see \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e).\u003c/p\u003e\n \u003cp\u003eTwo-tailed Mann-Whitney U tests were conducted to compare APAs, step characteristics and balance scores, between the two groups, while two-tailed Wilcoxon signed-rank tests were used to compare APAs and first step characteristics in the PD group when turning was initiated with the most affected side versus the least affected side. Spearman\u0026rsquo;s rank correlation coefficients were calculated to describe the relationships between APAs (total displacement features) and first step characteristics in turning, and between people\u0026rsquo;s balance and adopted turning strategies.\u003c/p\u003e\n \u003cp\u003eTime normalised weight-shift waveforms for each group were compared using the coefficients of multiple correlation (CMC, \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e) to investigate intra-group variability.\u003c/p\u003e\n \u003cp\u003eStatistical analysis was carried out using SPSS (v.28, IBM Corp, Armonk, NY, USA). A customised function written in Matlab was used to perform the CMC analysis. For all analyses, the level of significance was set to \u0026alpha;\u0026thinsp;=\u0026thinsp;0.05.\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003eA total of 22 pwPD and 17 healthy older adults were included in the final analysis. Five participants (3 pwPD) were excluded due to technical issues during data collection, and sixteen (11 pwPD) were excluded because they did not have at least three trials suitable for APA analysis. Of 22 pwPD included, 7 self-identified as experiencing freezing of gait based on the first item of the NFOG-Q. Two of these experienced freezing during the testing session. Participant characteristics are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003esummarises the participants characteristics. pwPD\u0026thinsp;=\u0026thinsp;people with Parkinson\u0026rsquo;s; UPDRS \u0026ndash; III\u0026thinsp;=\u0026thinsp;Unified Parkinson\u0026rsquo;s Disease Rating Scale-Part III; H\u0026amp;Y\u0026thinsp;=\u0026thinsp;Hoehn and Yahr Stage; SD\u0026thinsp;=\u0026thinsp;standard deviation; IQR\u0026thinsp;=\u0026thinsp;interquartile range; FOG\u0026thinsp;=\u0026thinsp;freezing of gait; NFOG\u0026thinsp;=\u0026thinsp;new freezing of gait questionnaire.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHealthy Older Adults\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePeople with PD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003cp\u003eFemale, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9F (53%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10F (46%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003cp\u003eyears, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73.41\u0026thinsp;\u0026plusmn;\u0026thinsp;8.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68.96\u0026thinsp;\u0026plusmn;\u0026thinsp;8.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight\u003c/p\u003e \u003cp\u003emetres, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.69\u0026thinsp;\u0026plusmn;\u0026thinsp;.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody Mass\u003c/p\u003e \u003cp\u003ekilograms, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e74.84\u0026thinsp;\u0026plusmn;\u0026thinsp;16.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75.20\u0026thinsp;\u0026plusmn;\u0026thinsp;16.94\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMiniBEST\u003c/p\u003e \u003cp\u003escore, median\u0026thinsp;\u0026plusmn;\u0026thinsp;IQR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUPDRS-III\u003c/p\u003e \u003cp\u003escore, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.68\u0026thinsp;\u0026plusmn;\u0026thinsp;13.74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u0026amp;Y\u003c/p\u003e \u003cp\u003estage, median\u0026thinsp;\u0026plusmn;\u0026thinsp;IQR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFOG\u003c/p\u003e \u003cp\u003epwPD and FOG, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (32%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNFOG\u003c/p\u003e \u003cp\u003escore, mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003e(only for pwPD and FOG)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.46\u003c/p\u003e \u003cp\u003e(7 People)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eCharacteristics of APAs in turning\u003c/h2\u003e \u003cp\u003eDescriptive data of the APAs and first step characteristics for the healthy older adults\u0026rsquo; group are reported in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The variability of APAs in turning was high as shown by the reported coefficients of variation and the CMC analysis (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). However, no features unique to APAs in turning were identified during visual inspections of CoP trajectories before turning. We observed that step length and velocity positively correlated with APA1 (p\u0026thinsp;=\u0026thinsp;.002, r\u0026thinsp;=\u0026thinsp;.627 and p\u0026thinsp;\u0026lt;\u0026thinsp;.001, r\u0026thinsp;=\u0026thinsp;534, respectively), APA2 (p\u0026thinsp;\u0026lt;\u0026thinsp;.001, r\u0026thinsp;=\u0026thinsp;.529 and p\u0026thinsp;=\u0026thinsp;.006, r\u0026thinsp;=\u0026thinsp;.414, respectively), and weight-shift (p\u0026thinsp;\u0026lt;\u0026thinsp;.001, r\u0026thinsp;=\u0026thinsp;.574 and p\u0026thinsp;=\u0026thinsp;.002, r\u0026thinsp;=\u0026thinsp;.490, respectively).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003esummarises the study's main results. Data is reported as median\u0026thinsp;\u0026plusmn;\u0026thinsp;interquartile range. BOS\u0026thinsp;=\u0026thinsp;base of support; m\u0026thinsp;=\u0026thinsp;metres; s\u0026thinsp;=\u0026thinsp;seconds; ms\u0026thinsp;=\u0026thinsp;milliseconds; cm\u0026thinsp;=\u0026thinsp;centimetres; CMC\u0026thinsp;=\u0026thinsp;coefficients of multiple correlation. Significant differences are highlighted in bold. Please note that APA1, APA2 and weight shift amplitudes reported in the table are normalised for the BOS.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOutcome Variable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHealthy Controls\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePeople with PD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMiniBest\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOS (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.769\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA1 Duration (ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e127\u0026thinsp;\u0026plusmn;\u0026thinsp;122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e130\u0026thinsp;\u0026plusmn;\u0026thinsp;61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.664\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA1 Amplitude AP (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.232\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA1 Amplitude ML (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.190\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA1 Amplitude Total (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.181\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA1 Velocity (m/s)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.10\u0026thinsp;\u0026plusmn;\u0026thinsp;.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA2 Duration (ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73\u0026thinsp;\u0026plusmn;\u0026thinsp;27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e64\u0026thinsp;\u0026plusmn;\u0026thinsp;56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.267\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA2 Amplitude AP (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.008\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA2 Amplitude ML (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4\u0026thinsp;\u0026plusmn;\u0026thinsp;.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.017\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA2 Amplitude Total (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.002\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAPA2 Velocity (m/s)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.27\u0026thinsp;\u0026plusmn;\u0026thinsp;.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.19\u0026thinsp;\u0026plusmn;\u0026thinsp;.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.457\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWeight Shift Duration (ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e321\u0026thinsp;\u0026plusmn;\u0026thinsp;216\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e328\u0026thinsp;\u0026plusmn;\u0026thinsp;122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.944\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWeight Shift Amplitude (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.0\u0026thinsp;\u0026plusmn;\u0026thinsp;12.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37.5\u0026thinsp;\u0026plusmn;\u0026thinsp;9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.017\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWeight Shift Velocity (m/s)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.27\u0026thinsp;\u0026plusmn;\u0026thinsp;.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.077\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTime to Foot Off (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21\u0026thinsp;\u0026plusmn;\u0026thinsp;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.424\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStep Length (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.0\u0026thinsp;\u0026plusmn;\u0026thinsp;17.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.021\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStep Velocity (m/s)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.01\u0026thinsp;\u0026plusmn;\u0026thinsp;2.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.51\u0026thinsp;\u0026plusmn;\u0026thinsp;1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e.039\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCMC Coefficient\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eHealthy older adults showed a clear preference for initiating a turn towards the right (~\u0026thinsp;84% of turns). Furthermore, as participants could self-select both the turn direction and the initiating leg, we identified two possible strategies: i) enlarge the BoS by initiating the turn with the leg in the same direction of turn (here called ipsilateral initiation); ii) reducing the BoS by initiating the turn with the leg opposite of the direction of the turn (here called contralateral initiation). No associations were found between balance scores and the adopted turning strategies (p\u0026thinsp;\u0026gt;\u0026thinsp;.05). Frequencies of the different turning strategies are reported in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ea summarises the frequency of turns for the Parkinson's group and the healthy control group, categorized by turning direction and stepping leg. Ipsilateral (CCW/L and CW/R) and contralateral (CCW/R and CW/L) initiations are here presented in detail. CCW\u0026thinsp;=\u0026thinsp;Counterclockwise turn; CW\u0026thinsp;=\u0026thinsp;Clockwise turn; L\u0026thinsp;=\u0026thinsp;Left stepping foot; R\u0026thinsp;=\u0026thinsp;Right stepping foot.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"12\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCCW\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCW\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCCW/L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCCW/R\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eCCW R/L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eCW/L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eCW/R\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eCW R/L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eTotal Turns\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePwPD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e252\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e152\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e320\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePercentage\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e78.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e56.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e41.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e31.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e47.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e60.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e207\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e118\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e116\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e246\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePercentage\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e84.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e47.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e52.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e30.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e36.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e47.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e56.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eb summarises the turning strategies of people with PD based on their most/least affected side (according to the UPDRS-III scores). R\u0026thinsp;=\u0026thinsp;Right; L\u0026thinsp;=\u0026thinsp;Left; M\u0026thinsp;=\u0026thinsp;Most Affected Side; L\u0026thinsp;=\u0026thinsp;Least Affected Side.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMost Affected Side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eParticipant\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTurn Direction M\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTurn Direction L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStep M\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStep L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eTurn M / Step M\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eTurn M/ Step L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eTurn L / Step M\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eTurn L/ Step L\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eTotal Turns\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePFOG22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePNFOG21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003ePercentage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e48.73646\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e51.26354\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e44.60432\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e55.39568\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e27.89855\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20.65217\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e16.30435\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e35.14493\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e13.85\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003eHERE\u003c/b\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e(Because of the layout Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e is at the end of the document)\u003c/h2\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003eComparisons between HC and PD\u003c/h2\u003e \u003cp\u003eDifferences between pwPD and healthy older adults were observed for both APAs and first step characteristics. Specifically, compared to healthy older people, pwPD showed smaller APA2 values for anteroposterior, mediolateral and total displacement (p\u0026thinsp;=\u0026thinsp;.008 r\u0026thinsp;=\u0026thinsp;.42; p\u0026thinsp;=\u0026thinsp;.017 r\u0026thinsp;=\u0026thinsp;.38; p\u0026thinsp;=\u0026thinsp;.002, r\u0026thinsp;=\u0026thinsp;.50, respectively) as well as reduced total weight-shifts (p\u0026thinsp;=\u0026thinsp;.017, r\u0026thinsp;=\u0026thinsp;.39). PwPD showed slower APA1 (p\u0026thinsp;\u0026lt;\u0026thinsp;.001, r\u0026thinsp;=\u0026thinsp;.94) but similar velocities of APA2 (p\u0026thinsp;=\u0026thinsp;.457, r\u0026thinsp;=\u0026thinsp;.12) and weight-shift (p\u0026thinsp;=\u0026thinsp;.077, r\u0026thinsp;=\u0026thinsp;.29) in comparison to healthy older people. Step length was shorter in pwPD compared to healthy older people (p\u0026thinsp;=\u0026thinsp;.021, r\u0026thinsp;=\u0026thinsp;.37); further steps were slower in PwPD (p\u0026thinsp;=\u0026thinsp;.039, r\u0026thinsp;=\u0026thinsp;.33). PwPD showed similar variability in APAs compared to healthy controls (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In pwPD, we observed a lack of significant correlations between step length and velocity with APA1 (p\u0026thinsp;\u0026gt;\u0026thinsp;.05, r\u0026thinsp;=\u0026thinsp;.211 and p\u0026thinsp;\u0026gt;\u0026thinsp;.05, r\u0026thinsp;=\u0026thinsp;.173, respectively) and APA2 (p\u0026thinsp;\u0026gt;\u0026thinsp;.05, r\u0026thinsp;=\u0026thinsp;.213 and p\u0026thinsp;\u0026gt;\u0026thinsp;.05, r\u0026thinsp;=\u0026thinsp;.218, respectively). Correlations were statistically similar between HC and pwPD for weight-shift (p\u0026thinsp;\u0026lt;\u0026thinsp;.001, r\u0026thinsp;=\u0026thinsp;.500 and p\u0026lt;, r\u0026thinsp;=\u0026thinsp;.554, respectively). No other notable differences were observed.\u003c/p\u003e \u003cp\u003eSimilarly to healthy older adults, pwPD showed a clear preference for initiating a turn towards the right (~\u0026thinsp;79% of turns; see Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e). A significant association was found between balance scores and the frequency of contralateral initiation of turns (p\u0026thinsp;=\u0026thinsp;.016, r\u0026thinsp;=\u0026thinsp;.533).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eComparison of APAs between turns towards most/least affected side\u003c/h2\u003e \u003cp\u003ePeople with PD were overall more likely to initiate a turn using strategies that increased their BoS (ipsilateral initiation: ~63% of turns) compared to strategies that reduced it (contralateral initiation: ~37% of turns, see Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e). However, pwPD with poorer balance (miniBEST\u0026thinsp;\u0026lt;\u0026thinsp;20) used contralateral initiations less often (13% of turns) than pwPD who had better balance (miniBEST\u0026thinsp;\u0026ge;\u0026thinsp;20, 38% of turns). There were no clear preferences in turning direction dictated by the most/least affected side.\u003c/p\u003e \u003cp\u003eSince most participants had a clear preference for a specific turning direction, only 8 participants with PD were included in the comparison of APAs and step characteristics between the most and least affected side. No significant differences were observed in either APAs or step characteristics between turns towards the most versus least affected side.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe current study characterised APAs prior to turning in healthy older adults and pwPD. Our findings show that APAs in turning share several features with those preceding forward gait initiation [\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e], albeit with preparatory adjustments primarily occurring along the mediolateral direction. Additionally, our results highlight key differences between healthy older adults and pwPD in both APA features (i.e. amplitude but not duration) and first-step characteristics (i.e. step length and velocity). Interestingly, significant associations between APA features and step execution were found only in healthy older adults, suggesting that PD may disrupt the relation between task preparation and execution during turning.\u003c/p\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eAPAs in turning: features in uncontrived tasks\u003c/h2\u003e \u003cp\u003eAPAs prior to voluntary turning follow a similar fundamental pattern to those observed in forward gait initiation [\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e], reflecting the postural preparation required to displace the body during bipedal movements. Before turning, the CoP shifts backward and laterally under the stepping foot, transferring body weight onto the standing limb. This shift ensures a safe foot-off by reducing the distance between the centre of mass and the medial margin of the BoS. However, compared to forward gait initiation [\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e], and in line with our hypothesis, our data show that APA1 amplitude tends to be smaller and shorter during turning, aligning more closely with APA1 reported in lateral stepping [\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e]. We attribute this difference to the fact that, while turning on the spot does not require the anterior acceleration needed in forward gait initiation, it still demands a small and precise forward shift to avoid instability.\u003c/p\u003e \u003cp\u003eAPA2 and weight-shift characteristics did not show distinguishable differences from forward gait initiation, likely because these components are primarily related to the effective transfer of body weight onto the standing leg. However, we observed greater variability in these components during turning, as indicated by higher coefficients of variation and a much lower CMC. For example, in forward gait initiation, weight shift typically exhibits very low inter-personal variability (CMC\u0026thinsp;=\u0026thinsp;0.90) [\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e], while in the current study, we found substantial variability (CMC\u0026thinsp;=\u0026thinsp;0.22). Although some of this difference could be attributed to the more controlled nature of the task performed in Russo \u0026amp; Vannozzi's study and the higher number of trials, we believe that the increased variability observed in this study is more likely produced by the greater complexity of turning. In fact, turning involves movements along the transverse plane and allows for more strategies (i.e., turn direction and stepping leg) compared to forward gait initiation, which is limited to selecting the stepping leg.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eAPAs in turning: effects of Parkinson\u0026rsquo;s Disease\u003c/h2\u003e \u003cp\u003eIn line with our initial hypothesis, individuals with PD demonstrated impoverished APAs compared to healthy older adults. Specifically, pwPD exhibited reduced APA2 amplitude and smaller weight-shift components, as well as slower execution of APA1. These findings are consistent with previous research on forward gait initiation, where impaired APAs in PD were linked to difficulties in task execution and balance control [\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e]. The smaller APAs amplitudes observed in pwPD (APA2 and weight-shift) and the slower APA1 suggest a reduced capacity to adequately prepare for the dynamic demands of turning, potentially increasing the risk of falls during everyday tasks involving changes in body orientation due to altered weight shifts [\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e]. Furthermore, this may be indicative of deficits in both motor and postural control, suggesting an altered ability to precisely adjust the spatiotemporal characteristics of APAs to align with the motor program for the turning step, which may further compromise stability during turning. Taken together these results may explain why pwPD were overall more likely to adopt strategies that increased their BoS when initiating turning (~\u0026thinsp;63% of turns), compared to strategies that reduced it (~\u0026thinsp;37%). This preference for stability-enhancing strategies may reflect an adaptive response to their postural control impairments, as expanding the BoS may provide greater stability during dynamic movements such as turning.\u003c/p\u003e \u003cp\u003eInterestingly, while pwPD exhibited shorter and slower steps during turning initiation, no significant differences were found between the two groups for foot-off percentage or the duration of any of the APA components. Although this lack of difference may be partly confounded by our inclusion criteria (e.g., balance abilities) and the relatively small sample size (when taking into account the overall variability observed), we speculate that the temporal components of APAs in turning might be less impaired in the early stages of PD, especially during uncontrived turning, where preparatory mechanisms may be more preserved compared to spatial ones.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eTurning Side and APA Characteristics\u003c/h2\u003e \u003cp\u003eOur analysis of turns towards the most versus least affected side in pwPD did not reveal significant differences in APAs or step characteristics. Furthermore, pwPD overall preferred to use turning strategies that prioritised the increase of the BoS rather than showing a preference based on most/least affected side, which may indicate that, different to forward gait initiation, severity asymmetries only in turning play a minor role during turning [\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e]. Although we admittedly only had a relatively small sample size (8 pwPD), these findings corroborate results recently published by Seuthe and co-workers [\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e] who identified asymmetries in gait but not turning in people with mild-to-moderate PD. A possible explanation is that asymmetry may be apparent in relatively simple task (e.g. gait initiation), but it may be masked/no longer apparent in more complex tasks where other aspects (e.g. turning strategy) may play a more pivotal role. Turning requires a fine coordination between body segments, and compared to forward gait, it poses greater challenges for sensory integration [\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e] and it requires greater cognitive demands [\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e]. Furthermore, these factors are likely to be further exacerbated in less prescribed/contrived adaptive gait tasks, such as that used in the current study. Therefore, while this more naturalistic behaviour could serve to mask subtle differences, the current data suggests that these differences are not of a sufficient magnitude to be clinically important.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003ePotential implications for Rehabilitation and Clinical Practice\u003c/h2\u003e \u003cp\u003eResearch indicates that turning is more vulnerable to balance and functional impairments than forward walking due to its complex demands [\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e]. In fact, during turning, pwPD are more likely to experience freezing of gait or falls [\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e]. Impairments in APAs are considered a major contributor to difficulties with gait initiation in pwPD [\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e], and dysfunctional APAs have been proposed as a possible cause of freezing of gait [\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e]. However, it is often challenging to observe differences in APAs during gait initiation in participants who are ON-medication, as dopamine tends to improve APAs [\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e] especially in people with moderate PD and without FOG [\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e], potentially masking PD-related impairments in balance control. However, despite our relatively small sample consisting of individuals with mild-to-moderate PD tested ON medication, we were able to detect significant differences both in the preparatory phase of turning and in the first step. Although more work is necessary to improve the generalisability of our results, the sensitivity of turn initiation in detecting subtle changes in postural control makes it a promising candidate for its inclusion in clinical assessments.\u003c/p\u003e \u003cp\u003eWhile turning is generally associated with a narrower BoS in pwPD [\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e], we did not observe differences in self-selected BOS prior to turns in this uncontrived task. However, our results highlighted a significant association between balance ability and the adopted turning strategy in pwPD, with higher balance scores linked to more frequent use of contralateral turn initiation, implying a reduced BoS. Interestingly, this relationship was not observed in healthy older adults. Reducing the BoS when initiating a turn may represent a more challenging strategy as there is potential instability at the end of the first step, due to momentum in the direction of the turn that could push the centre of mass beyond the margins of the BoS. We believe that for individuals with good balance, contralateral initiation does not pose a significant threat. As such, we would not expect to observe any relationship between balance ability and turn-initiation strategy in healthy older adults. In contrast, pwPD, who demonstrated poorer overall balance, may adopt the ipsilateral initiation strategy as an active avoidance mechanism to reduce postural instability during turning.\u003c/p\u003e \u003cp\u003eOverall, pwPD with poorer balance (miniBEST\u0026thinsp;\u0026lt;\u0026thinsp;20) initiated turns using a contralateral strategy 13% of times, while those with better balance (miniBEST\u0026thinsp;\u0026ge;\u0026thinsp;20) did so 38% of times. This suggests that people still tend to adopt a strategy, when under no specific time-pressure, that poses a non-negligible risk to balance. These findings are reminiscent of observations of behavioural risk-taking in older adults [\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e], and the use of cross-stepping in nursing homes residents [\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e ]. In these studies, participants either selected higher risks tasks [\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e] or unnecessarily opted for strategies (i.e. cross-stepping) which narrow the BoS, thus posing an increased challenge for the balance system. In the context of this study, cross-stepping may be viewed as an extreme example of contralateral turn initiation. As such, this type of behaviour could be maladaptive and enhance fall risk.\u003c/p\u003e \u003cp\u003eFurthermore, as BoS reduction during turning is thought to be a key factor in falls [\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e], this suggests a possible rehabilitation strategy: encouraging pwPD who have high instability to avoid transitioning directly from walking to turning, but instead to break the task into two distinct steps. Recent evidence suggests that especially pwPD who experience freezing could benefit by incorporating pauses/breaks between tasks or during a freeze to regain control over their balance [\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eLimitations and future directions\u003c/h2\u003e \u003cp\u003eThis study has three main limitations. i) Uncontrived turning task resulting in a significant loss of data suitable for APA analysis (e.g., absence of pauses or lack of turns in a given direction among pwPD). However, we believe this is also a key strength of the study, as it provides valuable insights into turning initiation in a naturalistic context, making the findings more applicable to real-life situations. ii) Small sample size for comparing turns between the most and least affected sides in PD. The small sample size limited our ability to fully assess side-specific impairments in turning initiation. Future research with larger samples is needed to better understand how such asymmetries impact turning initiation in pwPD. Additionally, although participants were assessed in their ON-medication state, the specific effects of medication on APAs characteristics during turning were not explored, which represents an important area for future investigation. iii) Exclusion of participants with poor balance. Since individuals with poor balance, who are typically in the later stages of PD, were excluded from this study, the generalisability of these findings is limited. Including participants with more advanced balance impairments in future research would provide a more comprehensive understanding of turning difficulties across the full spectrum of PD severity.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, APAs prior to turning share several similarities with APAs prior to gait initiation. When compared to healthy older adults, people with PD exhibit significant impairments in APAs execution during turning, including reduced amplitude and slower execution, which may contribute to the high incidence of falls during turning in this population. Our findings underscore the need for targeted interventions to address these specific motor deficits and suggest that strategies promoting weight-shifting and a stable base of support may aid in mitigating fall risk. Future research should continue to explore the interplay between motor asymmetry, medication effects, and turning performance to further refine clinical approaches to balance rehabilitation in PD.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003e This work was funded by Parkinson\u0026rsquo;s UK (G-2007) and was supported by the National Institute for Health and Care Research Exeter Biomedical Research Centre. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConception and design - YR \u0026amp; WY Acquisition of data - YR, PL, JY, ZW and WY Data curation, formal analysis and visualisation - YR Writing original draft - YR \u0026amp; WYWriting review \u0026amp; editing - All the authorsFinal approval of the completed article - All the authorsFunding acquisition - WY, AN, MW, MN, EK, SL\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003e We thank the participants, the people who accompanied them in the laboratory, the members of Parkinson\u0026rsquo;s UK branches who have supported our recruitment as well as our Project Advisory Group for their contributions to study conception, design, interpretation of results and dissemination.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request. Video recordings cannot be made available in line with privacy regulations.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJacobs, J. V. \u0026amp; Horak, F. B. External postural perturbations induce multiple anticipatory postural adjustments when subjects cannot pre-select their stepping foot. \u003cem\u003eExp Brain Res\u003c/em\u003e \u003cstrong\u003e179\u003c/strong\u003e, 29\u0026ndash;42 (2007).\u003c/li\u003e\n\u003cli\u003eHiraoka, K., Matuo, Y., Iwata, A., Onishi, T. \u0026amp; Abe, K. The effects of external cues on ankle control during gait initiation in Parkinson\u0026rsquo;s disease. \u003cem\u003eParkinsonism Relat Disord\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 97\u0026ndash;102 (2006).\u003c/li\u003e\n\u003cli\u003eRosin, R., Topka, H. \u0026amp; Dichgans, J. 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N. \u003cem\u003eet al.\u003c/em\u003e Video capture of the circumstances of falls in elderly people residing in long-term care: An observational study. \u003cem\u003eThe Lancet\u003c/em\u003e \u003cstrong\u003e381\u003c/strong\u003e, 47\u0026ndash;54 (2013).\u003c/li\u003e\n\u003cli\u003eRusso, Y. \u003cem\u003eet al.\u003c/em\u003e Russo, Y., et al. \u0026quot;Can A Single-Session Of Weight-Shift Training Support People With Parkinson\u0026rsquo;s Step From A Freeze? in \u003cem\u003eMovement Disorders\u003c/em\u003e 107\u0026ndash;108 (2023).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"turn, biomechanics, APA, step, posture","lastPublishedDoi":"10.21203/rs.3.rs-6172807/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6172807/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAnticipatory postural adjustments (APAs) are crucial for maintaining postural stability during voluntary movements such as gait initiation. While APAs have been extensively studied in forward stepping, little is known about their characteristics during turning initiation. This study aimed to identify the characteristics of (i) APAs and subsequent first steps during turning in healthy older adults (HOA) and (ii) compare them to people with Parkinson\u0026rsquo;s (pwPD). Thirty-six pwPD (tested on medication) and 24 HOA performed self-paced uncontrived 360˚ turns which were embedded in a complex walking task. APAs and first step characteristics were recorded using motion capture and force plate data. For pwPD, APAs in turning were found to be primarily mediolateral, and of significantly reduced amplitude (median\u0026thinsp;=\u0026thinsp;.0065, 95% CI[.0053; .0089]) in comparison to HOA (median\u0026thinsp;=\u0026thinsp;.0110, 95% CI[.0073; .0181]). Unlike HOA there was no significant association between APAs and step characteristics. These findings suggest that APAs during turning are significantly impaired in pwPD, even when tested ON medication, and that this impairment may contribute to the turning difficulties often experienced by this population. Overall, these results have potential implications for clinical assessments and rehabilitation interventions, emphasising the need to tailor strategies to address turning challenges pwPD face in their daily life.\u003c/p\u003e","manuscriptTitle":"Characterising Anticipatory Postural Adjustments in Turning: A Comparison Between Healthy Older Adults and People with Parkinson’s Disease","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-12 05:40:38","doi":"10.21203/rs.3.rs-6172807/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-25T07:09:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-17T02:26:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-10T15:23:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"192313554862238808800943332970044121874","date":"2025-05-13T14:14:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"147565388945959726881201377824946390922","date":"2025-03-20T00:49:15+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-19T20:47:15+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-19T19:58:02+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-03-11T11:07:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-10T09:20:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-03-06T17:53:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4038ce14-3380-44dc-b2c2-e71bb26606f5","owner":[],"postedDate":"March 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":45520680,"name":"Biological sciences/Neuroscience/Diseases of the nervous system/Parkinsons disease"},{"id":45520681,"name":"Physical sciences/Engineering/Biomedical engineering"}],"tags":[],"updatedAt":"2025-12-29T16:01:11+00:00","versionOfRecord":{"articleIdentity":"rs-6172807","link":"https://doi.org/10.1038/s41598-025-33425-5","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-12-22 15:57:46","publishedOnDateReadable":"December 22nd, 2025"},"versionCreatedAt":"2025-03-12 05:40:38","video":"","vorDoi":"10.1038/s41598-025-33425-5","vorDoiUrl":"https://doi.org/10.1038/s41598-025-33425-5","workflowStages":[]},"version":"v1","identity":"rs-6172807","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6172807","identity":"rs-6172807","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}