Assessing the Impact of Backpack Design on Hikers Lumbar Extension and Centre of Pressure 

Assessing the Impact of Backpack Design on Hikers Lumbar Extension and Centre of Pressure | 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 Research Article Assessing the Impact of Backpack Design on Hikers Lumbar Extension and Centre of Pressure Timothy Grigg, Natalia Kabaliuk, Sibi Walter This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4740002/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Heavy backpacks are carried by hikers for prolonged walking periods. Backpack designs impact a hiker’s biomechanics. Methods: We assessed the impact of different backpacks on lumbar extension (LE) and centre of pressure (COP) among hikers. Regular hikers (n=8; age = 23.4±1.9, years; weight = 85.1±7.9, kgs; height = 185.3±3.8, cm) who met the eligibility criteria attended testing sessions to test a traditional backpack (TBP) and a balance backpack (BBP), against a no backpack control (NBP) on three different gradient conditions (flat, 0°; incline, 12°; decline, -12°). Walking tests (1.1m/s) were performed on a force plate-embedded treadmill with a surrounding marker-based motion capture system. Multiple separate two-way ANOVA tests assessed the backpack effect on LE and COP. Results: Dunnett’s multiple comparison Post Hoc test revealed significant variance (p < 0.05) for TBP and an insignificant variance for BBP for LE values. A consistent degree of forward trunk lean across all conditions was observed, with a pronounced LE observed when using the TBP. Insignificant variance in the hiker’s COP between the NBP and BBP across all gradients was observed. Conclusions: This suggests that hikers using a BBP might find their walking posture quite like their normal gait kinematics in comparison to using a TBP. Hiking Gait Posture Backpack Figures Figure 1 Background Long distance nature-based walking is a popular recreational physical activity [ 1 ]. In 2021, 1.14 million New Zealanders went on at least one hike [ 2 ], establishing itself as a popular outdoor activity. Hiking involves prolonged walking periods across varying terrain, exploring wilderness, and reaching remote destinations. Depending on the difficulty level, hiking expeditions can last several days with heavy loads of equipment carried on uphill and downhill slopes [ 3 ]. Carrying a heavy backpack for long walking periods may affect a hiker’s walking mechanics, and potentially lead to musculoskeletal strain. The weight of a typical backpack load reaches between 10–20% of a hiker’s body weight, therefore it is recommended that hikers use backpacks with supportive frame around the hip and sternum. Lumbar and cervical spine loading is influenced by a backpack’s design and weight distribution pattern [ 6 ]. Contemporary backpacks have indicated design considerations to improve the users’ postural biomechanics. Balance backpacks (BBP) are a uniquely designed carriage system that allows the user to balance loads posteriorly and anteriorly and have been reported to have less impact on a users' forward lean during gait [ 7 ]. Traditional backpacks (TBP) mainly have posterior loading during carriage, whereas a BBP concept aims to reduce the posterior loading impact and balances the load [ 8 ]. The loading differences between TBP and BBP suggests possible postural differences in the sagittal plane kinematics and kinetics. Efficient backpack carriage relies on strategic load placement [ 9 ]. The BBP may encourage lower energy expenditure, delaying fatigue onset [ 10 ]. Altering a TBP’s design to match the user’s anthropometry may reduce a user’s fatigue [ 11 ]. Studies investigating the relationship between gait and backpack carriage have identified certain influential biomechanical variables such as kinematics and kinetics [ 15 – 21 ], muscle activity [ 22 – 25 ], spatiotemporal parameters [ 26 , 27 ] and comfort [ 28 – 30 ]. Studies have assessed the biomechanical gait changes during military backpack [ 32 , 33 ] and school backpack carriage [ 34 ]. However, these findings may not apply to hikers because of the differences in backpack design, carrying loads, and participant characteristics. Changes to posture due to fatigue has been reported to affect sports performance [ 35 ]. Prolonged backpack carriage also affects the user’s postural stability [ 36 ]. Heavy posterior loading causes a higher lumbar forward lean [ 8 , 27 , 37 ] with significant changes observed when backpack loads reach 10% body weight (BW) among female hikers [ 19 ]. A decrease in maximum lumbar extension (LE), or a greater forward trunk lean occurs to compensate for the heavy posterior loading to maintain balance. Sagittal plane kinematic adjustments align the trunk optimally over the hip joint and minimises hip flexion leading to improved gait efficiency [ 15 ]. This is a learned adaptation among regular hikers who often carry heavy loads in uneven terrain [ 38 ]. This trunk angle adaptation has been observed in the stance phase of army men who often carry heavy loads during training drills [ 32 ]. Posterior loading shifts the line of gravity before the base of support, leading to trunk flexion as the head tilts forward to restore stability [ 28 ]. As a consequence, to maintain a forward field of view the neck must be hyperextended to look ahead and not at the ground [ 8 ]. Increased LE to maintain balance can lead to higher muscle activity in the semispinalis, erector spinae, and trapezius, which may result in lumbar fatigue, discomfort, and potential pain [ 37 ]. Both load distribution and load magnitude impacts carriage performance efficiency [ 39 ]. Ground reaction forces (GRF) provide insights into an individual’s postural stability, and backpack designs influence a user’s GRF [ 40 ]. To maintain dynamic body stability, GRF has been reported to increase in as the backpack load increases [ 15 , 19 , 21 ]. Centre of pressure (COP) is the specific point under a person's foot where the GRF is concentrated, and COP adjustments and adaptations are made to maintain balance and prevent falling. Placement and magnitude of loads applied during gait have been linked to COP measures of postural stability [ 41 ]. Anteroposterior COP displacement changes when the backpack loading increases by 5–10% of BW, compared to no load [ 42 ]. Analysing COP displacement path helps differentiate a normal and abnormal gait [ 43 ]. During each step cycle, the centre of mass travels from behind to the front of the support base, reflected in the COP displacement, smoothly transitioning the kinetic energy, and requiring less mechanical work to move [ 44 ]. Mechanical stress information is therefore relatable to COP displacement and GRFs and further relatable to joint contact forces, which have the potential towards developing pathological conditions in the lower body [ 15 ]. Considering the biomechanical changes backpack design and loading may place on a user, prolonged abnormal walking gait could lead to an early fatigue onset for a hiker. Therefore, this study aimed to investigate the design of two backpacks (TBP and BBP), assessing the different loading system changes when walking on a flat, incline and decline gradients as compared to NBP loading condition. The focus was exclusively on LE and COP as they are crucial factors that influence the kinematics and kinetic carriage dynamics. Therefore, the primary aim was to compare the LE and COP changes of hikers walking on a treadmill (flat) under three loading conditions (NBP, TBP and BBP). The secondary aim was to compare the LE and COP changes of hikers walking on a treadmill (incline and decline) under three loading conditions (NBP, TBP and BBP). Methods Study design This non-blinded observational cross section study was approved by the University of Canterbury’s Human Research Ethics Committee (Ref: 2023/104/LR). Participants were recruited via advertisements and had to meet the following criteria: 1) must have participated in at least one overnight hike in the past 12 months; 2) must have experience with carriage of hiking backpacks; 3) must be males between the ages of 18 and 40 years old, 4) and capable of giving voluntary consent. Subjects were excluded if they were under medication or had any medical condition at the time of the study. Eight participants (age: 23 ± 2 years; weight 85.1 ± 8 kgs; height: 185.4 ± 4 cm) provided written informed consent and volunteered to participate. Equipment The backpacks were fitted according to each manufacturer’s guidelines with shoulder strap adjustments being made to account for the participant's torso length, as well as both the backpack’s hip and sternum straps. Two different backpack designs were tested, a TBP and a BBP. The brand of these two backpacks and their images could be displayed to ensure no breach in the studies’ ethics agreement. Both TBP and BBP were loaded to 15% of each participant BW (12.5 ± 1.5kgs) with sandbags and weight plates [ 47 ]. Load distribution in the TBP was spread evenly along the spine and balanced bilaterally [ 39 ]. Similarly, the BBP load was distributed appropriately with the addition of front packs being loaded, with an anterior-posterior ratio of 3:7. Postural kinematics and kinetics were collected during backpack carriage using a 12-camera Optitrack mocap motion capture system, Motive (2.2.0 (48012)) and AMTI Treadmetrix force instrumented treadmill (XCIE6); sampling at 240Hz and 2000Hz, respectively. A gait 2392 reflective marker set was used during motion recording to collect postural kinematics data. A Plug In-Gait model, Opensim, used an inverse kinematic software to assess LE and COP during backpack carriage. The treadmills imbedded force plate provided COP coordinates which were used to assess the COP displacement values. Procedure An initial debriefing and familiarisation with testing equipment and protocol was conducted and completed with a five-minute treadmill warm-up on a flat gradient. Participant anthropometric measurements were then taken before preparing for the gait trials. A total of 29 reflective markers were then placed on the motion capture Velcro suit that was worn by the participants during testing; reflective markers were placed bilaterally on the acromion process, anterior superior iliac spine, sacrum, lateral femoral condyle, and lateral malleolus. During the three walking trials, participants were instructed to walk normally, “facing the direction they were walking while keeping their arms swing by their side in a natural manner with a posture that felt comfortable to maintain.” To simulate backpack carriage across varying outdoor terrain, three walking surface gradients were selected in a repeat-measure experiment design: 0° (flat), 12° (incline), and − 12° (decline). The belt speed of the instrumented treadmill was set at a consistent, comfortable walking speed of 1.1m/s [ 48 ]. During each trial, each gradient, ordered flat, incline then decline, was systematically assessed. Participants walked for two minutes with each backpack variation. The gradient was then adjusted and repeated to record the respective gradient conditions variables. Participants first completed the trial with no backpack (NBP). This was to collect the subject’s typical posture data during gait without any influencing variables [ 49 ]. Participants then completed the trials carrying either the TBP or BBP, in an equal randomised order, followed by a subsequent trial of the second backpack, collecting LE and COP data values for each backpack configuration across each surface gradient. A five-minute rest period was held between each trial. Raw data collected from the embedded force plate and motion capture system was processed accordingly and organised in Excel. Each step was distinguished between time stamps of consecutive peak vertical forces, which was the initial contact of the leading foot during double support. These defined steps were verified to be accurate using the correlating time between peaks, where further corrections were made if one step was either considerably longer or shorter than the others. The LE angle was measured from a line perpendicular to the ground, with a forward lean resulting in a negative extension value (decrease in LE), as seen in Fig. 1 . To analyse LE average, maximum and range of motion (ROM) statistics was used to assess overall changes in variables. The LE average was measured as the average lumbar angle during the specific step cycle. The LE maximum was measured as the largest forward lean (negative value) angle during the specific step cycle. The LE ROM was measured as the difference between the maximum and minimum LE angles during the specific step cycle. These statistics were used to allow a fuller understanding of the variable’s behaviour during a step. In line with this, the COP average, maximum and ROM statistics were also used. COP value was measured along the x-axis (anterior and posterior) from the calculated centre pressure point of the participant’s foot, with positive COP displacement values being placed further forward and negative further behind. The COP displacement average was measured as the average displacement distance during the specific step cycle. The COP displacement maximum was measured as the largest displacement distance during a specific step cycle. The COP displacement ROM was measured as the difference between the maximum and minimum displacement distance during a specific step cycle. The hikers were allowed to walk on the treadmill for 60 seconds to get accustomed to the gait pattern. Only the LE and COP data recorded in the second minute was used for analysis, with the average, maximum and ROM of each being averaged during each step. Statistical analysis All statistical analyses were performed on Prism (Version 10.1.1, GraphPad Software, LLC). Variable data distribution normality was assessed and verified using a Shapiro-Wilk test, indicating no significant data deviation from normality (p > 0.05). The LE and COP variables were analysed using separate repeat measure analysis of variance (two-way ANOVA) design to contrast the TBP and BBP with NBP, across the varying gradient conditions. The effect size was calculated in partial eta squared (η²) to quantify the size of variance, with magnified values approaching one indicating a larger portion of total variance. A “high” effect size was considered when η² > 0.14; a “medium” effect size was considered when η² > 0.06; and a “low” effect size was considered when η² > 0.01. Where significant effect levels were recognised, Dunnett’s multiple comparison test was utilised to differentiate the effect each backpack configuration had on the variable of interest. Type I error risk was reduced with Dunnett’s comparison correction (with a set alpha level of 0.05). Geisser-Greenhouse’s Epsilon correction was employed when data sphericity was violated. Results Lumbar extension The mean LE values are displayed in Table 1 . When tested under different gradients, the mean differences between NBP and TBP LE were 4.74º (flat), 3.75º (incline) and 5.68º (decline) for average LE ROM whereas it was 4.64º (flat), 3.56º (incline) and 4.95º (decline) for maximum LE ROM. In comparison, when tested under different gradients, the mean differences between NBP and BBP were 0.67º (flat), 0.23º (incline) and 1.23º (decline) for average LE ROM, whereas it was 0.87º (flat), 0.96º (incline) and 1.04º (decline) for maximum LE ROM. Backpack type exhibited a significant main effect (p < 0.001) on both average and maximum LE, as shown in Table 2 . Mean LE values suggested a consistent degree of forward lean across all conditions, with a more pronounced extension observed when using the TBP. The effect size of the backpack variable was high for both average and maximum LE values, accounting for 39% (η² = 0.385) and 30% (η² = 0.300) of the total variance, respectively. The backpack variable had a low effect on LE ROM (η² = 0.005). Dunnett’s post hoc comparison test revealed significant variance (p < 0.05) when using the TBP for both average and maximum LE values, while insignificant variance was observed with the BBP, suggesting that the TBP was the primary contributor to the variance in LE data, displayed in Table 3 . Gradient variation only had a significant main effect on average means and ROM means of LE, with both exhibiting high effect sizes (η² > 0.15). The backpack vs gradient interaction effect sizes for LE averages, maxima, and ROM mean variables were all medium to low (η² < 0.15). Table 1 Mean (SD) of lumbar extension and centre of pressure variables Variable and gradient Backpack Type NBP TBP BBP Average LE o Flat -11.56 ± (2.10) -16.30 ± (2.32) -12.23 ± (2.32) Incline -13.91 ± (1.89) -17.66 ± (2.37) -14.20 ± (2.53) Decline -9.64 ± (2.27) -15.32 ± (2.97) -10.88 ± (2.51) Maximum LE o Flat -13.06 ± (2.26) -17.70 ± (2.54) -13.92 ± (2.90) Incline -15.59 ± (2.08) -19.15 ± (2.66) -16.54 ± (3.33) Decline -12.03 ± (2.76) -15.79 ± (3.04) -13.07 ± (2.91) LE ROM o Flat 2.51 ± (0.38) 2.36 ± (0.54) 2.28 ± (0.51) Incline 2.72 ± (0.89) 2.98 ± (0.86) 3.09 ± (0.93) Decline 4.04 ± (0.89) 3.68 ± (1.44) 3.41 ± (1.06) Average COP displacement (mm) Flat 13.32 ± (7.31) 29.90 ± (8.21) 14.73 ± (8.28) Incline 35.31 ± (11.02) 41.92 ± (15.02) 37.89 ± (15.83) Decline -25.68 ± (9.22) -22.22 ± (11.84) -27.87 ± (6.45) Maximum COP displacement (mm) Flat 103.36 ± (3.51) 111.31 ± (13.51) 102.82 ± (9.62) Incline 124.40 ± (14.43) 137.62 ± (16.17) 133.31 ± (15.22) Decline 92.32 ± (19.98) 87.63 ± (14.69) 90.11 ± (21.01) COP ROM (mm) Flat 269.89 ± (23.73) 265.99 ± (24.96) 262.82 ± (12.34) Incline 292.39 ± (34.70) 293.53 ± (26.53) 295.93 ± (29.48) Decline 254.54 ± (34.22) 241.06 ± (32.14) 244.45 ± (29.34) Note: NBP, No Backpack; TBP, Traditional Backpack; BBP, Balance Backpack; COP, Centre of Pressure; ROM, Range of Motion Table 2 ANOVA analysis summary of backpack, gradient and interaction Variable Condition F ( p ) S Effect size (η²) Average LE o Backpack 192.9 (< 0.001) Yes 0.385 Gradient 4.008 (0.034) Yes 0.162 Maximum LE o Backpack 116 (< 0.001) Yes 0.300 LE ROM o Backpack 0.416 (0.626) No 0.005 Gradient 7.3 (< 0.001) Yes 0.554 Average COP displacement (mm) Backpack 28.4 (< 0.001) Yes 0.021 Gradient 69.7 (< 0.001) Yes 0.839 Interaction 4.44 (0.004) Yes 0.006 Maximum COP displacement (mm) Backpack 2.94 (0.070) No 0.009 Gradient 17.78 (< 0.001) Yes 0.579 Interaction 3.84 (0.010) Yes 0.024 COP ROM (mm) Backpack 1.37 (0.265) No 0.005 Gradient 6.31 (0.008) Yes 0.355 Note: F, F-statistics; S, Significant; ES, Effect Size; LE Lumbar Extension; COP Centre of Pressure; ROM Range of Motion Table 3 Post hoc comparison for significant backpack effects Variable Mean difference Adjusted p value TBP BBP TBP BBP Average LE o Flat 4.741 0.6687 < 0.001 0.374 Incline 3.746 0.2888 < 0.001 0.622 Decline 5.679 1.233 < 0.001 0.054 Maximum LE o Level 4.64 0.866 < 0.001 0.262 Incline 3.56 0.956 < 0.001 0.359 Decline 4.95 1.233 < 0.001 0.223 Average COP displacement (mm) Level -1.58 -0.138 0.002 0.491 Incline -0.763 -0.388 0.028 0.148 Decline -0.471 0.1 0.030 0.855 Note: TBP, Traditional Backpack; BBP, Balance Backpack; LE, Lumbar Extension; COP Centre of Pressure Centre of Pressure While using the TBP, average COP displacement displayed a mean increase (16.2mm) in the flat and incline gradient in front of the COP and a mean increase in the declining gradient behind the COP. No significant changes in mean values for COP displacement maximum and ROM were observed across all three different backpack condition. This was displayed in the mean COP values in Table 1 . When tested under different gradients, the mean differences between NBP and TBP were 15.8mm (flat), 7.6mm (incline) and 4.7mm (decline) for average COP displacement, whereas it was 7.7mm (flat), 12.8mm (incline) and − 5.1mm (decline) for maximum COP displacement. In comparison, when tested under different gradients, the mean differences between NBP and BBP were 1.4mm (flat), 3.9mm (incline) and − 1.0mm (decline) for average COP displacement, whereas it was − 1.0mm (flat), 9.5mm (incline) and − 2.2mm (decline) for maximum COP displacement. Backpack type exhibited a significant main effect (p < 0.001) only on the COP displacement average, see Table 2 . COP average had a high effect size (η² = 0.021) for backpack variance, while COP displacement maximum and ROM had a medium to low effect size when accounting for backpack variance. Dunnett’s Post Hoc comparisons test displayed significant variance (p > 0.05) using the TBP compared to NBP, and insignificant variance using the BBP compared to NBP, as displayed in Table 3 . The COP displacement average, maximum and ROM all showed high effect sizes when accounting for the different surface gradients (η² = 0.839, 0.579, 0.355, respectively). Average and maximum COP displacement variables both had high effect sizes for backpack vs gradient interaction, while COP ROM had a low effect size. The adjusted p-values for COP displacement average during flat, incline and decline gradient conditions highlighted this interaction (p = 0.002, 0.028, 0.030; respectively). Discussion This study investigated the biomechanics of hikers carrying different backpacks and compared them to their unloaded walking posture. More specifically the focus was on how LE and COP changed between unloaded and loaded conditions with different gradients. Simulated in a laboratory setting we found that LE and COP of a hiker was affected by the backpack design. Both LE and COP values displayed a significant response to backpack variation, but the ROM values were not statistically significantly different between the backpacks. This suggests that while general gait posture is leant further forward, the typical gait oscillation generally remains consistent with each backpack variation. All variables investigated, other than maximum LE, yielded varying mean values when walking on different gradient conditions. A greater forward-tilted LE was observed on the flat and the inclined gradients during backpack carriage and this was also observed during the declining gradient rather than being mitigated. Also, the BBP’s weight distribution had a significantly lower impact on COP displacement than the TBP. Lumbar Extension Comparing the two different loading system designs, the LE variables had a contrasting variance to NBP. During the flat, incline and decline gradient conditions, the TBP caused a significantly greater decrease in LE average and maximum values than the BBP when compared to the NBP, as seen in Table 1 . The mean differences between NBP and TBP for LE averages and maximum were the largest during the decline condition, followed by flat, and then incline. While the differences were insignificant between the NBP and BBP, as seen in Table 3 , this is a common effect of backpack carriage, which is more typical during posterior carriage. This aligns with previous results that less significant trunk angle change was reported between a non-traditional bag (lateral loading system) gait and a non-loaded gait, compared to a traditional bag [ 8 ]. A more upright gait posture is encouraged by positioning the user's centre of gravity nearer to the vertical axis of their support base. The anterior/posterior weight distribution of the BBP (30-to-70%) would have shifted the user's centre of gravity anteriorly, positioning further forward and nearer to its natural location down the body. This adjustment is supported by gait literacy considering backpack carriage has been indicated to have a significant effect on LE with loads higher than 15% BW [ 39 , 50 ]. Considering the purpose of the TBP and BBP for hiking, maintaining an efficient gait is crucial for prolonged walking. Prolonged backpack carriage with excessive LE can progressively strain and fatigue involved trunk muscles. Significant increases in rectus abdominis muscle activity have been reported during carriage as a counterbalance reaction to additional posterior load [ 47 ]. Our data indicates that the BBP promotes a lumbar position similar to an individual’s unloaded gait. Long walking periods with a loaded back might predispose hikers to overuse injuries. Overuse musculoskeletal injuries in the lower back are often related to motor control impairments in lumbopelvic stability. This has been reported across low-intensity sports such as hiking [ 51 ] and high-intensity sports like football [ 52 ], where overarching muscle activation may impede passive spine stiffening protection strategies during active movement. Lumbar movement has further been accounted to influence walking metabolic costs [ 27 ]. We found no significant differences in LE ROM, with no observable trends being displayed across all gradients. Previous research has indicated smaller LE ROM observed during backpack carriage to maintain a balanced gait, as excessive angular momentum due to potential thoracic angular velocities would potentially be too difficult to counterbalance [ 53 ]. In contrast to this statement, several other studies have also reported insignificant effect sizes when considering a step’s LE ROM during backpack carriage [ 54 , 55 ]. In our data, LE ROM remained unaffected by backpack variation, which could be attributed to the discrepancy between studies when distributing the posterior mass. We ensured an evenly distributed load through the pack’s internal compartment and specifically packed the mass closer to the user's back, extending uniformly from the shoulders down to the hips, thus minimising angular momentum compared to traditional backpacks. Centre of Pressure During every gait cycle, as weight transitions from the heel to the toe, the average displacement from the individual foot's centre pressure point determines whether the participant's weight is shifting forward or backward. Mean value trends, displayed in Table 1 , provide less obvious changes in COP. Further examination of the significant effect of backpack variation on COP displacement revealed a greater data variance with the TBP than the BBP, suggesting that the conventional posterior loading system demands more adaptive measures to preserve gait balance. While the anterior-posterior loading system naturally provides a more balanced distribution of load, the mean difference in COP displacement average, when comparing NBP to TBP was the largest on flat conditions and similar during the incline and decline conditions. This aligns with a meta-analysis finding on postural sway during loading where two factors were highlighted as significant influences on postural stability: 1) COP anterior-posterior sway was increased forward during carriage with larger loads and 2) COP anterior-posterior sway was increased further forward during posterior load placements compared to either balanced or anterior load placement [ 41 ]. The body’s mechanism to adapt to changes in its mass-inertia characteristics often explains postural sway, which has been reported to be present even during static standing while holding an additional mass [ 42 ]. The TBP creates an unnatural body mass inertia for biomechanical adjustment to maintain a stable gait. Furthermore, with the observed increase in vertical ground reaction forces during backpack carriage [ 21 ], a forward shift in the COP implies that the body will absorb the vertical ground reaction forces through an unnatural line of impact. Gait with an excessive forward lean increases angular impulse in hip extensors and knee flexors and decreases in the hip flexors and knee extensors [ 49 ]. Increasing the risk of musculoskeletal injuries as the system gets fatigued and less resilient to impact forces [ 24 , 56 ]. It is also interesting to note the significant interaction (backpack vs gradient), where the average COP displacement mean difference was less significant for both incline and decline between backpack variations. The influence of the TBP on average COP was reduced during sloped conditions, with diminished forward weight displacement. Uphill gait adaptations typically involve adjustments in the thorax, hip, knee, and ankle, while downhill adaptations are more highly centred around the knee and ankle [57]. Furthermore, knee movements change similarly as the tibiofemoral and patellofemoral joints handle compression forces inversely during incline or decline [ 48 ]. In relation to COP, it has been suggested that increased musculoskeletal activity and cognitive engagement result in reduced COP motion [ 41 ], providing an explanation of why our results demonstrated a reduced COP ROM during sloped gradients. Limitations The low sample size could be a limitation in this study. Only one gender of a certain stature was recruited so that the torso length could be standardised, to minimise confounding factors. The simulated lab environment allows for accurate movement analysis but sacrifices an accurate representation of real-life hiking conditions. Each backpack condition's effect on postural variables over a prolonged period of walking on uneven surfaces was limited to the acute changes observed on a consistently even treadmill belt. Future research conducted within typical hiking environments would provide more realistic results of each backpack’s influence on gait. Multiple two-way ANOVA tests were used under the assumption that homogeneity variances were not violated and therefore results and effect sizes between tests were comparable. We minimised potential bias through equal random backpack ordering and mandatory rest breaks between trials, however, we would have encountered limitations due to the nested structure of the data as repeated measures within participants were taken. An example of this is when participants put on and took off each backpack, there was potential for the Velcro suit, and therefore the sensor dots, to shift in relation to the body between trials. A mixed effect model therefore could have been more appropriate to account for these effects through a more flexible framework to analyse and compare the data. Conclusions By investigating the differences between the TBP and BBP loading designs, we determined that the BBP’s anterior-posterior loading system more closely replicated the unloaded gait pattern in comparison to the TBP. We found no significant variance in LE and COP variables when assessing the hiker’s gait during BBP carriage in comparison to their normal unloaded gait. This was consistent across flat, inclining and declining gradients. Based on the lab simulation, our data suggests that hikers walking long distances carrying a balanced backpack might find their posture quite similar to their normal walking gait. Declarations Ethics approval and consent to participate. The University of Canterbury’s Human Research Ethics Committee (Ref: 2023/104/LR) approved this study. All participants were voluntary and provided written consent to participate. Data availability and data sharing statement Not applicable. Competing interests All authors declare that they have no conflicts of interest relevant to the content of this review. Funding None to declare. Contributions and consent for publication. According to the definition given by the International Committee of Medical Journal Editors (ICMJE), the authors consent for publication and the authors listed qualify for authorship based on making one or more of the substantial contributions to the intellectual content of: Conception and design (TG, NK, SW); and/or Acquisition of data (TG); and/or Analysis and interpretation of data (TG, NK, SW); and/or Participated in drafting of the manuscript (TG, NK, SW); and/or Critical revision of the manuscript for important intellectual content (TG, NK, SW). Acknowledgements None. References Lynch, P. and M. Dibben, Exploring motivations for adventure recreation events: a New Zealand study . Annals of leisure research, 2016. 19(1): p. 80–97. Summer tramping outlook . MSC 2022; Available from: https://www.mountainsafety.org.nz Knight, C.A. and G.E. Caldwell, Muscular and metabolic costs of uphill backpacking: are hiking poles beneficial? Medicine and science in sports and exercise, 2000. 32(12): p. 2093–2101. Miranda, D.L., et al., Sensory enhancing insoles improve athletic performance during a hexagonal agility task . Journal of biomechanics, 2016. 49(7): p. 1058–1063. Stefanyshyn, D.J. and J.W. Wannop, Biomechanics research and sport equipment development . Sports Engineering, 2015. 18: p. 191–202. Orloff, H., M. White, and L. Tanaka. The effects of fatigue and backpack design on posture . in ISBS-Conference Proceedings Archive . 1999. Lloyd, R. and C.B. Cooke, Kinetic changes associated with load carriage using two rucksack designs . Ergonomics, 2000. 43(9): p. 1331–1341. Dahl, K.D., et al., Load distribution and postural changes in young adults when wearing a traditional backpack versus the BackTpack . Gait & posture, 2016. 45: p. 90–96. Liu, B.-S., Backpack load positioning and walking surface slope effects on physiological responses in infantry soldiers . International Journal of Industrial Ergonomics, 2007. 37(9–10): p. 754–760. Wells-Fahling, K., Effects of Two Backpack Weight Distributions on Perceptual and Physiological Measures During Walking. 2002. Mahachandra, M., et al. Ergonomics redesign of mountain backpack for female hikers in Indonesia . in Proceedings of the International Conference on Industrial Engineering and Operations Management . 2021. Coombes, J.S. and C. Kingswell, Biomechanical and physiological comparison of conventional webbing and the M83 assault vest . Applied ergonomics, 2005. 36(1): p. 49–53. Legg, S.J., A. Barr, and D.I. Hedderley, Subjective perceptual methods for comparing backpacks in the field . Ergonomics, 2003. 46(9): p. 935–955. Silva, L.M. and N. Stergiou, Chap. 7 - The basics of gait analysis , in Biomechanics and Gait Analysis , N. Stergiou, Editor. 2020, Academic Press. p. 225–250. Castro, M.P., et al., The influence of gait cadence on the ground reaction forces and plantar pressures during load carriage of young adults . Applied ergonomics, 2015. 49: p. 41–46. Fiolkowski, P., et al., Changes in gait kinematics and posture with the use of a front pack . Ergonomics, 2006. 49(9): p. 885–894. Liew, B., K. Netto, and S. Morris, Increase in Leg Stiffness Reduces Joint Work During Backpack Carriage Running at Slow Velocities . Journal of applied biomechanics, 2017. 33(5): p. 347–353. Oberhofer, K., et al., The Influence of Backpack Weight and Hip Belt Tension on Movement and Loading in the Pelvis and Lower Limbs during Walking. Applied bionics and biomechanics, 2018. 2018: p. 4671956-7. Simpson, K.M., B.J. Munro, and J.R. Steele, Effects of prolonged load carriage on ground reaction forces, lower limb kinematics and spatio-temporal parameters in female recreational hikers . Ergonomics, 2012. 55(3): p. 316–326. Tong, J., et al., Effects of Stature and Load Carriage on the Running Biomechanics of Healthy Men . IEEE transactions on biomedical engineering, 2023. PP(8): p. 2445–2453. Watanabe, K. and Y. Wang, Influence of Backpack Load and Gait Speed on Plantar Forces During Walking . Research in sports medicine, 2013. 21(4): p. 395–401. Hardie, R., et al., The Effects of Bag Style on Muscle Activity of the Trapezius, Erector Spinae and Latissimus Dorsi During Walking in Female University Students . Journal of human kinetics, 2015. 45(1): p. 39–47. Li, S.S.W. and D.H.K. Chow, Comparison of Predictions Between an EMG-Assisted Approach and Two Optimization-Driven Approaches for Lumbar Spine Loading During Walking With Backpack Loads . Human factors, 2020. 62(4): p. 565–577. Simpson, K.M., B.J. Munro, and J.R. Steele, Backpack load affects lower limb muscle activity patterns of female hikers during prolonged load carriage . Journal of electromyography and kinesiology, 2011. 21(5): p. 782788. Yali, H., et al., The muscle activation patterns of lower limb during stair climbing at different backpack load . Acta of bioengineering and biomechanics, 2015. 17(4): p. 1320. Dames, K.D. and J.D. Smith, Effects of load carriage and footwear on spatiotemporal parameters, kinematics, and metabolic cost of walking . Gait & posture, 2015. 42(2): p. 122–126. Rosa, R.G.d., et al., Inclined Weight-Loaded Walking at Different Speeds: Pelvis-Shoulder Coordination, Trunk Movements and Cost of Transport . Journal of motor behavior, 2018. 50(1): p. 73–79. Abaraogu, U.O., et al., Immediate responses to backpack carriage on postural angles in young adults: A crossover randomized self-controlled study with repeated measures . Work (Reading, Mass.), 2017. 57(1): p. 87–93. Legg, S.J., L. Perko, and P. Campbell, Subjective perceptual methods for comparing backpacks . Ergonomics, 1997. 40(8): p. 809–817. Stuempfle, K.J., D.G. Drury, and A.L. Wilson, Effect of load position on physiological and perceptual responses during load carriage with an internal frame backpack . Ergonomics, 2004. 47(7): p. 784–789. Chockalingam, N., Introduction , in Clinical Biomechanics in Human Locomotion , A. Horwood and N. Chockalingam, Editors. 2023, Academic Press. p. xxiii-xxv. Attwells, R.L., et al., Influence of carrying heavy loads on soldiers' posture, movements and gait . Ergonomics, 2006. 49(14): p. 1527–1537. Lee, J., Y.-J. Yoon, and C.S. Shin, The Effect of Backpack Load Carriage on the Kinetics and Kinematics of Ankle and Knee Joints During Uphill Walking . Journal of applied biomechanics, 2017. 33(6): p. 397–405. Brackley, H.M., J.M. Stevenson, and J.C. Selinger, Effect of backpack load placement on posture and spinal curvature in prepubescent children . Work (Reading, Mass.), 2009. 32(3): p. 351–360. Salavati, M., et al., Changes in postural stability with fatigue of lower extremity frontal and sagittal plane movers . Gait & Posture, 2007. 26(2): p. 214–218. Li, S.S.W., Y.-P. Zheng, and D.H.K. Chow, Changes of lumbosacral joint compression force profile when walking caused by backpack loads . Human movement science, 2019. 66: p. 164–172. Simpson, K.M., B.J. Munro, and J.R. Steele, Effect of load mass on posture, heart rate and subjective responses of recreational female hikers to prolonged load carriage . Applied ergonomics, 2011. 42(3): p. 403–410. Liu, Y., et al., Effects of Backpack Loads on Leg Muscle Activation during Slope Walking . Applied sciences, 2020. 10(14): p. 4890. Devroey, C., et al., Evaluation of the effect of backpack load and position during standing and walking using biomechanical, physiological and subjective measures . Ergonomics, 2007. 50(5): p. 728–742. Ren, L., R.K. Jones, and D. Howard, Dynamic analysis of load carriage biomechanics during level walking . Journal of biomechanics, 2005. 38(4): p. 853–863. Martin, J., et al., Effects of load carriage on measures of postural sway in healthy, young adults: A systematic review and meta-analysis . Applied Ergonomics, 2023. 106: p. 103893. Roberts, M., et al., Changes in postural sway and gait characteristics as a consequence of anterior load carriage . Gait & posture, 2018. 66: p. 139–145. Jamshidi, N., et al., Differences in center of pressure trajectory between normal and steppage gait . Journal of research in medical sciences, 2010. 15(1): p. 33–40. Heglund, N.C., et al., Energy-saving gait mechanics with head-supported loads . Nature (London), 1995. 375(6526): p. 52–54. Machado, Á.S., et al., Effects of different hydration supports on stride kinematics, comfort, and impact accelerations during running . Gait & posture, 2022. 97: p. 115–121. Leroux, A., J. Fung, and H. Barbeau, Postural adaptation to walking on inclined surfaces: I. Normal strategies . Gait & Posture, 2002. 15(1): p. 64–74. Al-Khabbaz, Y.S.S.M., T. Shimada, and M. Hasegawa, The effect of backpack heaviness on trunk-lower extremity muscle activities and trunk posture . Gait & Posture, 2008. 28(2): p. 297–302. Alexander, N. and H. Schwameder, Lower limb joint forces during walking on the level and slopes at different inclinations . Gait & posture, 2016. 45: p. 137–142. Lewis, C.L. and S.A. Sahrmann, Effect of posture on hip angles and moments during gait . Manual Therapy, 2015. 20(1): p. 176–182. Li, S.S.W. and D.H.K. Chow, Multi-objective analysis for assessing simultaneous changes in regional spinal curvatures under backpack carriage in young adults . Ergonomics, 2016. 59(11): p. 1494–1504. Hawke, A.L. and R.L. Jensen, Are Trekking Poles Helping or Hindering Your Hiking Experience? A Review . Wilderness & Environmental Medicine, 2020. 31(4): p. 482–488. Nandlall, N., et al., The effect of low back pain and lower limb injury on lumbar multifidus muscle morphology and function in university soccer players . BMC Musculoskeletal Disorders, 2020. 21(1). LaFiandra, M., et al., How do load carriage and walking speed influence trunk coordination and stride parameters? Journal of Biomechanics, 2003. 36(1): p. 87–95. Morrison, A., J. Hale, and S. Brown, Joint range of motion entropy changes in response to load carriage in military personnel . Human Movement Science, 2019. 66: p. 249257. Smith, B., et al., Influence of carrying a backpack on pelvic tilt, rotation, and obliquity in female college students . Gait & Posture, 2006. 23(3): p. 263–267. Safran, M.R., et al., Strains across the Acetabular Labrum during Hip Motion:A Cadaveric Model . The American Journal of Sports Medicine, 2011. 39(1_suppl): p. 92–102. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4740002","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":331264062,"identity":"9e1b899c-1830-4f8a-9c13-df60ca8af005","order_by":0,"name":"Timothy Grigg","email":"","orcid":"","institution":"University of Canterbury","correspondingAuthor":false,"prefix":"","firstName":"Timothy","middleName":"","lastName":"Grigg","suffix":""},{"id":331264063,"identity":"781997b0-0522-4041-98a5-f0211a61c136","order_by":1,"name":"Natalia Kabaliuk","email":"","orcid":"","institution":"University of Canterbury","correspondingAuthor":false,"prefix":"","firstName":"Natalia","middleName":"","lastName":"Kabaliuk","suffix":""},{"id":331264064,"identity":"9812ee82-9a57-40f3-a4e5-095210bb8276","order_by":2,"name":"Sibi Walter","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABY0lEQVRIie2RP2vCQBTALxzE5amrgWL6ES4IgaLYr5IQ0LFCl3QRj0BcClkj/RJ1c+hw4UFdYl0DdmgQOiuF0kKhPf8EtLXOpeQ33N/34927R0hOzl+EAsHd/Yk86sm5sdkqvSOKStcTyDAu41qru8OKjKGHFPxV0fvFCDsu6mU9ELTjNoCNo/7T8m6ql2+CaH41wgsmaLpQRt2twrBkYRijMfApoWHcAhbbnIfPMyN8RGpMYjy7FWqtosRqplBgWPTRYvdSkQswhc09EDOLJI6qcR8ZE8Qkig/Zw7x95RPMacq9D/Fg6YlTeN8ohVepVLJicF8RYCYyCxHCYjKLslFglYXt19KWtTgMIXbgPEn54Fo4xjBxahqP20xDuKzYvpU9LJjgS8et62UapXNwm1UtcMTiTTT1amKnSz6qs9K4P1ws/ezHtnjrURxom+R01SPr+2n3Z+BO73rHbnNycnL+P1+HHY+eyhVWhgAAAABJRU5ErkJggg==","orcid":"","institution":"University of Canterbury","correspondingAuthor":true,"prefix":"","firstName":"Sibi","middleName":"","lastName":"Walter","suffix":""}],"badges":[],"createdAt":"2024-07-14 23:59:20","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-4740002/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4740002/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":61946851,"identity":"bbd834e4-9fcb-499f-baec-2301700b75c1","added_by":"auto","created_at":"2024-08-07 11:41:45","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":42592,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement diagram of lumbar extension and centre of pressure\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4740002/v1/f5b97b59200753f79c326dca.jpg"},{"id":78563196,"identity":"ce704d6e-b0ea-4cbf-a764-a8891f060cb8","added_by":"auto","created_at":"2025-03-15 04:31:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":832377,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4740002/v1/60606bd9-2ad0-4791-99ec-7f72583945a6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":" Assessing the Impact of Backpack Design on Hikers Lumbar Extension and Centre of Pressure ","fulltext":[{"header":"Background","content":"\u003cp\u003eLong distance nature-based walking is a popular recreational physical activity [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In 2021, 1.14\u0026nbsp;million New Zealanders went on at least one hike [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], establishing itself as a popular outdoor activity. Hiking involves prolonged walking periods across varying terrain, exploring wilderness, and reaching remote destinations. Depending on the difficulty level, hiking expeditions can last several days with heavy loads of equipment carried on uphill and downhill slopes [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Carrying a heavy backpack for long walking periods may affect a hiker\u0026rsquo;s walking mechanics, and potentially lead to musculoskeletal strain. The weight of a typical backpack load reaches between 10\u0026ndash;20% of a hiker\u0026rsquo;s body weight, therefore it is recommended that hikers use backpacks with supportive frame around the hip and sternum. Lumbar and cervical spine loading is influenced by a backpack\u0026rsquo;s design and weight distribution pattern [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Contemporary backpacks have indicated design considerations to improve the users\u0026rsquo; postural biomechanics. Balance backpacks (BBP) are a uniquely designed carriage system that allows the user to balance loads posteriorly and anteriorly and have been reported to have less impact on a users' forward lean during gait [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Traditional backpacks (TBP) mainly have posterior loading during carriage, whereas a BBP concept aims to reduce the posterior loading impact and balances the load [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The loading differences between TBP and BBP suggests possible postural differences in the sagittal plane kinematics and kinetics. Efficient backpack carriage relies on strategic load placement [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The BBP may encourage lower energy expenditure, delaying fatigue onset [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Altering a TBP\u0026rsquo;s design to match the user\u0026rsquo;s anthropometry may reduce a user\u0026rsquo;s fatigue [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStudies investigating the relationship between gait and backpack carriage have identified certain influential biomechanical variables such as kinematics and kinetics [\u003cspan additionalcitationids=\"CR16 CR17 CR18 CR19 CR20\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], muscle activity [\u003cspan additionalcitationids=\"CR23 CR24\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], spatiotemporal parameters [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] and comfort [\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Studies have assessed the biomechanical gait changes during military backpack [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] and school backpack carriage [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. However, these findings may not apply to hikers because of the differences in backpack design, carrying loads, and participant characteristics.\u003c/p\u003e \u003cp\u003eChanges to posture due to fatigue has been reported to affect sports performance [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Prolonged backpack carriage also affects the user\u0026rsquo;s postural stability [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Heavy posterior loading causes a higher lumbar forward lean [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] with significant changes observed when backpack loads reach 10% body weight (BW) among female hikers [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. A decrease in maximum lumbar extension (LE), or a greater forward trunk lean occurs to compensate for the heavy posterior loading to maintain balance. Sagittal plane kinematic adjustments align the trunk optimally over the hip joint and minimises hip flexion leading to improved gait efficiency [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. This is a learned adaptation among regular hikers who often carry heavy loads in uneven terrain [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. This trunk angle adaptation has been observed in the stance phase of army men who often carry heavy loads during training drills [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Posterior loading shifts the line of gravity before the base of support, leading to trunk flexion as the head tilts forward to restore stability [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. As a consequence, to maintain a forward field of view the neck must be hyperextended to look ahead and not at the ground [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Increased LE to maintain balance can lead to higher muscle activity in the semispinalis, erector spinae, and trapezius, which may result in lumbar fatigue, discomfort, and potential pain [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Both load distribution and load magnitude impacts carriage performance efficiency [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Ground reaction forces (GRF) provide insights into an individual\u0026rsquo;s postural stability, and backpack designs influence a user\u0026rsquo;s GRF [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. To maintain dynamic body stability, GRF has been reported to increase in as the backpack load increases [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Centre of pressure (COP) is the specific point under a person's foot where the GRF is concentrated, and COP adjustments and adaptations are made to maintain balance and prevent falling. Placement and magnitude of loads applied during gait have been linked to COP measures of postural stability [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Anteroposterior COP displacement changes when the backpack loading increases by 5\u0026ndash;10% of BW, compared to no load [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Analysing COP displacement path helps differentiate a normal and abnormal gait [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. During each step cycle, the centre of mass travels from behind to the front of the support base, reflected in the COP displacement, smoothly transitioning the kinetic energy, and requiring less mechanical work to move [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Mechanical stress information is therefore relatable to COP displacement and GRFs and further relatable to joint contact forces, which have the potential towards developing pathological conditions in the lower body [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Considering the biomechanical changes backpack design and loading may place on a user, prolonged abnormal walking gait could lead to an early fatigue onset for a hiker. Therefore, this study aimed to investigate the design of two backpacks (TBP and BBP), assessing the different loading system changes when walking on a flat, incline and decline gradients as compared to NBP loading condition. The focus was exclusively on LE and COP as they are crucial factors that influence the kinematics and kinetic carriage dynamics. Therefore, the primary aim was to compare the LE and COP changes of hikers walking on a treadmill (flat) under three loading conditions (NBP, TBP and BBP). The secondary aim was to compare the LE and COP changes of hikers walking on a treadmill (incline and decline) under three loading conditions (NBP, TBP and BBP).\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThis non-blinded observational cross section study was approved by the University of Canterbury\u0026rsquo;s Human Research Ethics Committee (Ref: 2023/104/LR). Participants were recruited via advertisements and had to meet the following criteria: 1) must have participated in at least one overnight hike in the past 12 months; 2) must have experience with carriage of hiking backpacks; 3) must be males between the ages of 18 and 40 years old, 4) and capable of giving voluntary consent. Subjects were excluded if they were under medication or had any medical condition at the time of the study. Eight participants (age: 23\u0026thinsp;\u0026plusmn;\u0026thinsp;2 years; weight 85.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8 kgs; height: 185.4\u0026thinsp;\u0026plusmn;\u0026thinsp;4 cm) provided written informed consent and volunteered to participate.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEquipment\u003c/h2\u003e \u003cp\u003e The backpacks were fitted according to each manufacturer\u0026rsquo;s guidelines with shoulder strap adjustments being made to account for the participant's torso length, as well as both the backpack\u0026rsquo;s hip and sternum straps. Two different backpack designs were tested, a TBP and a BBP. The brand of these two backpacks and their images could be displayed to ensure no breach in the studies\u0026rsquo; ethics agreement. Both TBP and BBP were loaded to 15% of each participant BW (12.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5kgs) with sandbags and weight plates [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Load distribution in the TBP was spread evenly along the spine and balanced bilaterally [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Similarly, the BBP load was distributed appropriately with the addition of front packs being loaded, with an anterior-posterior ratio of 3:7. Postural kinematics and kinetics were collected during backpack carriage using a 12-camera Optitrack mocap motion capture system, Motive (2.2.0 (48012)) and AMTI Treadmetrix force instrumented treadmill (XCIE6); sampling at 240Hz and 2000Hz, respectively. A gait 2392 reflective marker set was used during motion recording to collect postural kinematics data. A Plug In-Gait model, Opensim, used an inverse kinematic software to assess LE and COP during backpack carriage. The treadmills imbedded force plate provided COP coordinates which were used to assess the COP displacement values.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eProcedure\u003c/h2\u003e \u003cp\u003eAn initial debriefing and familiarisation with testing equipment and protocol was conducted and completed with a five-minute treadmill warm-up on a flat gradient. Participant anthropometric measurements were then taken before preparing for the gait trials. A total of 29 reflective markers were then placed on the motion capture Velcro suit that was worn by the participants during testing; reflective markers were placed bilaterally on the acromion process, anterior superior iliac spine, sacrum, lateral femoral condyle, and lateral malleolus. During the three walking trials, participants were instructed to walk normally, \u0026ldquo;facing the direction they were walking while keeping their arms swing by their side in a natural manner with a posture that felt comfortable to maintain.\u0026rdquo; To simulate backpack carriage across varying outdoor terrain, three walking surface gradients were selected in a repeat-measure experiment design: 0\u0026deg; (flat), 12\u0026deg; (incline), and \u0026minus;\u0026thinsp;12\u0026deg; (decline). The belt speed of the instrumented treadmill was set at a consistent, comfortable walking speed of 1.1m/s [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. During each trial, each gradient, ordered flat, incline then decline, was systematically assessed. Participants walked for two minutes with each backpack variation. The gradient was then adjusted and repeated to record the respective gradient conditions variables. Participants first completed the trial with no backpack (NBP). This was to collect the subject\u0026rsquo;s typical posture data during gait without any influencing variables [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Participants then completed the trials carrying either the TBP or BBP, in an equal randomised order, followed by a subsequent trial of the second backpack, collecting LE and COP data values for each backpack configuration across each surface gradient. A five-minute rest period was held between each trial. Raw data collected from the embedded force plate and motion capture system was processed accordingly and organised in Excel. Each step was distinguished between time stamps of consecutive peak vertical forces, which was the initial contact of the leading foot during double support. These defined steps were verified to be accurate using the correlating time between peaks, where further corrections were made if one step was either considerably longer or shorter than the others. The LE angle was measured from a line perpendicular to the ground, with a forward lean resulting in a negative extension value (decrease in LE), as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. To analyse LE average, maximum and range of motion (ROM) statistics was used to assess overall changes in variables. The LE average was measured as the average lumbar angle during the specific step cycle. The LE maximum was measured as the largest forward lean (negative value) angle during the specific step cycle. The LE ROM was measured as the difference between the maximum and minimum LE angles during the specific step cycle. These statistics were used to allow a fuller understanding of the variable\u0026rsquo;s behaviour during a step. In line with this, the COP average, maximum and ROM statistics were also used. COP value was measured along the x-axis (anterior and posterior) from the calculated centre pressure point of the participant\u0026rsquo;s foot, with positive COP displacement values being placed further forward and negative further behind. The COP displacement average was measured as the average displacement distance during the specific step cycle. The COP displacement maximum was measured as the largest displacement distance during a specific step cycle. The COP displacement ROM was measured as the difference between the maximum and minimum displacement distance during a specific step cycle. The hikers were allowed to walk on the treadmill for 60 seconds to get accustomed to the gait pattern. Only the LE and COP data recorded in the second minute was used for analysis, with the average, maximum and ROM of each being averaged during each step.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll statistical analyses were performed on Prism (Version 10.1.1, GraphPad Software, LLC). Variable data distribution normality was assessed and verified using a Shapiro-Wilk test, indicating no significant data deviation from normality (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The LE and COP variables were analysed using separate repeat measure analysis of variance (two-way ANOVA) design to contrast the TBP and BBP with NBP, across the varying gradient conditions. The effect size was calculated in partial eta squared (η\u0026sup2;) to quantify the size of variance, with magnified values approaching one indicating a larger portion of total variance. A \u0026ldquo;high\u0026rdquo; effect size was considered when η\u0026sup2; \u0026gt; 0.14; a \u0026ldquo;medium\u0026rdquo; effect size was considered when η\u0026sup2; \u0026gt; 0.06; and a \u0026ldquo;low\u0026rdquo; effect size was considered when η\u0026sup2; \u0026gt; 0.01. Where significant effect levels were recognised, Dunnett\u0026rsquo;s multiple comparison test was utilised to differentiate the effect each backpack configuration had on the variable of interest. Type I error risk was reduced with Dunnett\u0026rsquo;s comparison correction (with a set alpha level of 0.05). Geisser-Greenhouse\u0026rsquo;s Epsilon correction was employed when data sphericity was violated.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eLumbar extension\u003c/h2\u003e \u003cp\u003eThe mean LE values are displayed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. When tested under different gradients, the mean differences between NBP and TBP LE were 4.74\u0026ordm; (flat), 3.75\u0026ordm; (incline) and 5.68\u0026ordm; (decline) for average LE ROM whereas it was 4.64\u0026ordm; (flat), 3.56\u0026ordm; (incline) and 4.95\u0026ordm; (decline) for maximum LE ROM. In comparison, when tested under different gradients, the mean differences between NBP and BBP were 0.67\u0026ordm; (flat), 0.23\u0026ordm; (incline) and 1.23\u0026ordm; (decline) for average LE ROM, whereas it was 0.87\u0026ordm; (flat), 0.96\u0026ordm; (incline) and 1.04\u0026ordm; (decline) for maximum LE ROM. Backpack type exhibited a significant main effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) on both average and maximum LE, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Mean LE values suggested a consistent degree of forward lean across all conditions, with a more pronounced extension observed when using the TBP. The effect size of the backpack variable was high for both average and maximum LE values, accounting for 39% (η\u0026sup2; = 0.385) and 30% (η\u0026sup2; = 0.300) of the total variance, respectively. The backpack variable had a low effect on LE ROM (η\u0026sup2; = 0.005). Dunnett\u0026rsquo;s post hoc comparison test revealed significant variance (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) when using the TBP for both average and maximum LE values, while insignificant variance was observed with the BBP, suggesting that the TBP was the primary contributor to the variance in LE data, displayed in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Gradient variation only had a significant main effect on average means and ROM means of LE, with both exhibiting high effect sizes (η\u0026sup2; \u0026gt; 0.15). The backpack vs gradient interaction effect sizes for LE averages, maxima, and ROM mean variables were all medium to low (η\u0026sup2; \u0026lt; 0.15).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMean (SD) of lumbar extension and centre of pressure variables\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"char\" char=\"\u0026plusmn;\" 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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVariable and gradient\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBackpack Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNBP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTBP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eBBP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAverage LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-11.56 \u0026plusmn; (2.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-16.30 \u0026plusmn; (2.32)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-12.23 \u0026plusmn; (2.32)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-13.91 \u0026plusmn; (1.89)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-17.66 \u0026plusmn; (2.37)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-14.20 \u0026plusmn; (2.53)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-9.64 \u0026plusmn; (2.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-15.32 \u0026plusmn; (2.97)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-10.88 \u0026plusmn; (2.51)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMaximum LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-13.06 \u0026plusmn; (2.26)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-17.70 \u0026plusmn; (2.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-13.92 \u0026plusmn; (2.90)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-15.59 \u0026plusmn; (2.08)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-19.15 \u0026plusmn; (2.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-16.54 \u0026plusmn; (3.33)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e-12.03 \u0026plusmn; (2.76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-15.79 \u0026plusmn; (3.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-13.07 \u0026plusmn; (2.91)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eLE ROM \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e2.51 \u0026plusmn; (0.38)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.36 \u0026plusmn; (0.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.28 \u0026plusmn; (0.51)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e2.72 \u0026plusmn; (0.89)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.98 \u0026plusmn; (0.86)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.09 \u0026plusmn; (0.93)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e4.04 \u0026plusmn; (0.89)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.68 \u0026plusmn; (1.44)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.41 \u0026plusmn; (1.06)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eAverage COP displacement (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.32 \u0026plusmn; (7.31)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e29.90 \u0026plusmn; (8.21)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e14.73 \u0026plusmn; (8.28)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35.31 \u0026plusmn; (11.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e41.92 \u0026plusmn; (15.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e37.89 \u0026plusmn; (15.83)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-25.68 \u0026plusmn; (9.22)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e-22.22 \u0026plusmn; (11.84)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-27.87 \u0026plusmn; (6.45)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eMaximum COP displacement (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e103.36 \u0026plusmn; (3.51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e111.31 \u0026plusmn; (13.51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e102.82 \u0026plusmn; (9.62)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e124.40 \u0026plusmn; (14.43)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e137.62 \u0026plusmn; (16.17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e133.31 \u0026plusmn; (15.22)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e92.32 \u0026plusmn; (19.98)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e87.63 \u0026plusmn; (14.69)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e90.11 \u0026plusmn; (21.01)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCOP ROM (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e269.89 \u0026plusmn; (23.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e265.99 \u0026plusmn; (24.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e262.82 \u0026plusmn; (12.34)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e292.39 \u0026plusmn; (34.70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e293.53 \u0026plusmn; (26.53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e295.93 \u0026plusmn; (29.48)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e254.54 \u0026plusmn; (34.22)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e241.06 \u0026plusmn; (32.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e244.45 \u0026plusmn; (29.34)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003cem\u003eNote: NBP, No Backpack; TBP, Traditional Backpack; BBP, Balance Backpack; COP, Centre of Pressure; ROM, Range of Motion\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\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\u003eANOVA analysis summary of backpack, gradient and interaction\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\".\" 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=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCondition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF (\u003cem\u003ep\u003c/em\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEffect size (η\u0026sup2;)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAverage LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e192.9 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.385\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGradient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.008 (0.034)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.162\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e116 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.300\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLE ROM \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.416 (0.626)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGradient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.3 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.554\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage COP displacement (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28.4 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.021\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGradient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e69.7 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.839\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInteraction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.44 (0.004)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum COP displacement (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.94 (0.070)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.009\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGradient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.78 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.579\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInteraction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.84 (0.010)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.024\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOP ROM (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBackpack\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.37 (0.265)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGradient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.31 (0.008)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.355\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cem\u003eNote: F, F-statistics; S, Significant; ES, Effect Size; LE Lumbar Extension; COP Centre of Pressure; ROM Range of Motion\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \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\u003ePost hoc comparison for significant backpack effects\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" 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=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMean difference\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eAdjusted p value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTBP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBBP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTBP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eBBP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlat\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.741\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.6687\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.374\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.746\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2888\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.622\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.679\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.054\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum LE \u003csup\u003eo\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLevel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.866\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.262\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.956\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.359\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.223\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage COP displacement (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLevel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-1.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.491\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIncline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-0.763\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.388\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.148\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-0.471\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.030\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.855\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003cem\u003eNote: TBP, Traditional Backpack; BBP, Balance Backpack; LE, Lumbar Extension; COP Centre of Pressure\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eCentre of Pressure\u003c/h2\u003e \u003cp\u003eWhile using the TBP, average COP displacement displayed a mean increase (16.2mm) in the flat and incline gradient in front of the COP and a mean increase in the declining gradient behind the COP. No significant changes in mean values for COP displacement maximum and ROM were observed across all three different backpack condition. This was displayed in the mean COP values in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. When tested under different gradients, the mean differences between NBP and TBP were 15.8mm (flat), 7.6mm (incline) and 4.7mm (decline) for average COP displacement, whereas it was 7.7mm (flat), 12.8mm (incline) and \u0026minus;\u0026thinsp;5.1mm (decline) for maximum COP displacement. In comparison, when tested under different gradients, the mean differences between NBP and BBP were 1.4mm (flat), 3.9mm (incline) and \u0026minus;\u0026thinsp;1.0mm (decline) for average COP displacement, whereas it was \u0026minus;\u0026thinsp;1.0mm (flat), 9.5mm (incline) and \u0026minus;\u0026thinsp;2.2mm (decline) for maximum COP displacement. Backpack type exhibited a significant main effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) only on the COP displacement average, see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. COP average had a high effect size (η\u0026sup2; = 0.021) for backpack variance, while COP displacement maximum and ROM had a medium to low effect size when accounting for backpack variance. Dunnett\u0026rsquo;s Post Hoc comparisons test displayed significant variance (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) using the TBP compared to NBP, and insignificant variance using the BBP compared to NBP, as displayed in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The COP displacement average, maximum and ROM all showed high effect sizes when accounting for the different surface gradients (η\u0026sup2; = 0.839, 0.579, 0.355, respectively). Average and maximum COP displacement variables both had high effect sizes for backpack vs gradient interaction, while COP ROM had a low effect size. The adjusted p-values for COP displacement average during flat, incline and decline gradient conditions highlighted this interaction (p\u0026thinsp;=\u0026thinsp;0.002, 0.028, 0.030; respectively).\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study investigated the biomechanics of hikers carrying different backpacks and compared them to their unloaded walking posture. More specifically the focus was on how LE and COP changed between unloaded and loaded conditions with different gradients. Simulated in a laboratory setting we found that LE and COP of a hiker was affected by the backpack design. Both LE and COP values displayed a significant response to backpack variation, but the ROM values were not statistically significantly different between the backpacks. This suggests that while general gait posture is leant further forward, the typical gait oscillation generally remains consistent with each backpack variation. All variables investigated, other than maximum LE, yielded varying mean values when walking on different gradient conditions. A greater forward-tilted LE was observed on the flat and the inclined gradients during backpack carriage and this was also observed during the declining gradient rather than being mitigated. Also, the BBP\u0026rsquo;s weight distribution had a significantly lower impact on COP displacement than the TBP.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eLumbar Extension\u003c/h2\u003e \u003cp\u003eComparing the two different loading system designs, the LE variables had a contrasting variance to NBP. During the flat, incline and decline gradient conditions, the TBP caused a significantly greater decrease in LE average and maximum values than the BBP when compared to the NBP, as seen in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The mean differences between NBP and TBP for LE averages and maximum were the largest during the decline condition, followed by flat, and then incline. While the differences were insignificant between the NBP and BBP, as seen in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, this is a common effect of backpack carriage, which is more typical during posterior carriage. This aligns with previous results that less significant trunk angle change was reported between a non-traditional bag (lateral loading system) gait and a non-loaded gait, compared to a traditional bag [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. A more upright gait posture is encouraged by positioning the user's centre of gravity nearer to the vertical axis of their support base. The anterior/posterior weight distribution of the BBP (30-to-70%) would have shifted the user's centre of gravity anteriorly, positioning further forward and nearer to its natural location down the body. This adjustment is supported by gait literacy considering backpack carriage has been indicated to have a significant effect on LE with loads higher than 15% BW [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Considering the purpose of the TBP and BBP for hiking, maintaining an efficient gait is crucial for prolonged walking. Prolonged backpack carriage with excessive LE can progressively strain and fatigue involved trunk muscles. Significant increases in rectus abdominis muscle activity have been reported during carriage as a counterbalance reaction to additional posterior load [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Our data indicates that the BBP promotes a lumbar position similar to an individual\u0026rsquo;s unloaded gait. Long walking periods with a loaded back might predispose hikers to overuse injuries. Overuse musculoskeletal injuries in the lower back are often related to motor control impairments in lumbopelvic stability. This has been reported across low-intensity sports such as hiking [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e] and high-intensity sports like football [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e], where overarching muscle activation may impede passive spine stiffening protection strategies during active movement. Lumbar movement has further been accounted to influence walking metabolic costs [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. We found no significant differences in LE ROM, with no observable trends being displayed across all gradients. Previous research has indicated smaller LE ROM observed during backpack carriage to maintain a balanced gait, as excessive angular momentum due to potential thoracic angular velocities would potentially be too difficult to counterbalance [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. In contrast to this statement, several other studies have also reported insignificant effect sizes when considering a step\u0026rsquo;s LE ROM during backpack carriage [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. In our data, LE ROM remained unaffected by backpack variation, which could be attributed to the discrepancy between studies when distributing the posterior mass. We ensured an evenly distributed load through the pack\u0026rsquo;s internal compartment and specifically packed the mass closer to the user's back, extending uniformly from the shoulders down to the hips, thus minimising angular momentum compared to traditional backpacks.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eCentre of Pressure\u003c/h2\u003e \u003cp\u003eDuring every gait cycle, as weight transitions from the heel to the toe, the average displacement from the individual foot's centre pressure point determines whether the participant's weight is shifting forward or backward. Mean value trends, displayed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, provide less obvious changes in COP. Further examination of the significant effect of backpack variation on COP displacement revealed a greater data variance with the TBP than the BBP, suggesting that the conventional posterior loading system demands more adaptive measures to preserve gait balance. While the anterior-posterior loading system naturally provides a more balanced distribution of load, the mean difference in COP displacement average, when comparing NBP to TBP was the largest on flat conditions and similar during the incline and decline conditions. This aligns with a meta-analysis finding on postural sway during loading where two factors were highlighted as significant influences on postural stability: 1) COP anterior-posterior sway was increased forward during carriage with larger loads and 2) COP anterior-posterior sway was increased further forward during posterior load placements compared to either balanced or anterior load placement [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The body\u0026rsquo;s mechanism to adapt to changes in its mass-inertia characteristics often explains postural sway, which has been reported to be present even during static standing while holding an additional mass [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The TBP creates an unnatural body mass inertia for biomechanical adjustment to maintain a stable gait. Furthermore, with the observed increase in vertical ground reaction forces during backpack carriage [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], a forward shift in the COP implies that the body will absorb the vertical ground reaction forces through an unnatural line of impact. Gait with an excessive forward lean increases angular impulse in hip extensors and knee flexors and decreases in the hip flexors and knee extensors [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Increasing the risk of musculoskeletal injuries as the system gets fatigued and less resilient to impact forces [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. It is also interesting to note the significant interaction (backpack vs gradient), where the average COP displacement mean difference was less significant for both incline and decline between backpack variations. The influence of the TBP on average COP was reduced during sloped conditions, with diminished forward weight displacement. Uphill gait adaptations typically involve adjustments in the thorax, hip, knee, and ankle, while downhill adaptations are more highly centred around the knee and ankle [57]. Furthermore, knee movements change similarly as the tibiofemoral and patellofemoral joints handle compression forces inversely during incline or decline [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. In relation to COP, it has been suggested that increased musculoskeletal activity and cognitive engagement result in reduced COP motion [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e], providing an explanation of why our results demonstrated a reduced COP ROM during sloped gradients.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThe low sample size could be a limitation in this study. Only one gender of a certain stature was recruited so that the torso length could be standardised, to minimise confounding factors. The simulated lab environment allows for accurate movement analysis but sacrifices an accurate representation of real-life hiking conditions. Each backpack condition's effect on postural variables over a prolonged period of walking on uneven surfaces was limited to the acute changes observed on a consistently even treadmill belt. Future research conducted within typical hiking environments would provide more realistic results of each backpack\u0026rsquo;s influence on gait. Multiple two-way ANOVA tests were used under the assumption that homogeneity variances were not violated and therefore results and effect sizes between tests were comparable. We minimised potential bias through equal random backpack ordering and mandatory rest breaks between trials, however, we would have encountered limitations due to the nested structure of the data as repeated measures within participants were taken. An example of this is when participants put on and took off each backpack, there was potential for the Velcro suit, and therefore the sensor dots, to shift in relation to the body between trials. A mixed effect model therefore could have been more appropriate to account for these effects through a more flexible framework to analyse and compare the data.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eBy investigating the differences between the TBP and BBP loading designs, we determined that the BBP\u0026rsquo;s anterior-posterior loading system more closely replicated the unloaded gait pattern in comparison to the TBP. We found no significant variance in LE and COP variables when assessing the hiker\u0026rsquo;s gait during BBP carriage in comparison to their normal unloaded gait. This was consistent across flat, inclining and declining gradients. Based on the lab simulation, our data suggests that hikers walking long distances carrying a balanced backpack might find their posture quite similar to their normal walking gait.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe University of Canterbury\u0026rsquo;s Human Research Ethics Committee (Ref: 2023/104/LR) approved this study. All participants were voluntary and provided written consent to participate.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability and data sharing statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare that they have no conflicts of interest relevant to the content of this review.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions and consent for publication.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAccording to the definition given by the International Committee of Medical Journal Editors (ICMJE), the authors consent for publication and the authors listed qualify for authorship based on making one or more of the substantial contributions to the intellectual content of: \u0026nbsp;\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eConception and design (TG, NK, SW); and/or \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eAcquisition of data (TG); and/or \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eAnalysis and interpretation of data (TG, NK, SW); and/or \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eParticipated in drafting of the manuscript (TG, NK, SW); and/or \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eCritical revision of the manuscript for important intellectual content (TG, NK, SW).\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLynch, P. and M. Dibben, \u003cem\u003eExploring motivations for adventure recreation events: a New Zealand study\u003c/em\u003e. Annals of leisure research, 2016. 19(1): p. 80\u0026ndash;97.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSummer tramping \u003cem\u003eoutlook\u003c/em\u003e. MSC 2022; Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.mountainsafety.org.nz\u003c/span\u003e\u003cspan address=\"https://www.mountainsafety.org.nz\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKnight, C.A. and G.E. Caldwell, \u003cem\u003eMuscular and metabolic costs of uphill backpacking: are hiking poles beneficial?\u003c/em\u003e Medicine and science in sports and exercise, 2000. 32(12): p. 2093\u0026ndash;2101.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiranda, D.L., et al., \u003cem\u003eSensory enhancing insoles improve athletic performance during a hexagonal agility task\u003c/em\u003e. Journal of biomechanics, 2016. 49(7): p. 1058\u0026ndash;1063.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStefanyshyn, D.J. and J.W. Wannop, \u003cem\u003eBiomechanics research and sport equipment development\u003c/em\u003e. Sports Engineering, 2015. 18: p. 191\u0026ndash;202.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOrloff, H., M. White, and L. Tanaka. \u003cem\u003eThe effects of fatigue and backpack design on posture\u003c/em\u003e. in \u003cem\u003eISBS-Conference Proceedings Archive\u003c/em\u003e. 1999.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLloyd, R. and C.B. Cooke, \u003cem\u003eKinetic changes associated with load carriage using two rucksack designs\u003c/em\u003e. Ergonomics, 2000. 43(9): p. 1331\u0026ndash;1341.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDahl, K.D., et al., \u003cem\u003eLoad distribution and postural changes in young adults when wearing a traditional backpack versus the BackTpack\u003c/em\u003e. Gait \u0026amp; posture, 2016. 45: p. 90\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, B.-S., \u003cem\u003eBackpack load positioning and walking surface slope effects on physiological responses in infantry soldiers\u003c/em\u003e. International Journal of Industrial Ergonomics, 2007. 37(9\u0026ndash;10): p. 754\u0026ndash;760.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWells-Fahling, K., \u003cem\u003eEffects of Two Backpack Weight Distributions on Perceptual and Physiological Measures During Walking.\u003c/em\u003e 2002.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMahachandra, M., et al. \u003cem\u003eErgonomics redesign of mountain backpack for female hikers in Indonesia\u003c/em\u003e. in \u003cem\u003eProceedings of the International Conference on Industrial Engineering and Operations Management\u003c/em\u003e. 2021.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCoombes, J.S. and C. Kingswell, \u003cem\u003eBiomechanical and physiological comparison of conventional webbing and the M83 assault vest\u003c/em\u003e. Applied ergonomics, 2005. 36(1): p. 49\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLegg, S.J., A. Barr, and D.I. Hedderley, \u003cem\u003eSubjective perceptual methods for comparing backpacks in the field\u003c/em\u003e. Ergonomics, 2003. 46(9): p. 935\u0026ndash;955.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSilva, L.M. and N. Stergiou, Chap. 7 \u003cem\u003e- The basics of gait analysis\u003c/em\u003e, in \u003cem\u003eBiomechanics and Gait Analysis\u003c/em\u003e, N. Stergiou, Editor. 2020, Academic Press. p. 225\u0026ndash;250.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCastro, M.P., et al., \u003cem\u003eThe influence of gait cadence on the ground reaction forces and plantar pressures during load carriage of young adults\u003c/em\u003e. Applied ergonomics, 2015. 49: p. 41\u0026ndash;46.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFiolkowski, P., et al., \u003cem\u003eChanges in gait kinematics and posture with the use of a front pack\u003c/em\u003e. Ergonomics, 2006. 49(9): p. 885\u0026ndash;894.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiew, B., K. Netto, and S. Morris, \u003cem\u003eIncrease in Leg Stiffness Reduces Joint Work During Backpack Carriage Running at Slow Velocities\u003c/em\u003e. Journal of applied biomechanics, 2017. 33(5): p. 347\u0026ndash;353.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOberhofer, K., et al., \u003cem\u003eThe Influence of Backpack Weight and Hip Belt Tension on Movement and Loading in the Pelvis and Lower Limbs during Walking.\u003c/em\u003e Applied bionics and biomechanics, 2018. 2018: p. 4671956-7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSimpson, K.M., B.J. Munro, and J.R. Steele, \u003cem\u003eEffects of prolonged load carriage on ground reaction forces, lower limb kinematics and spatio-temporal parameters in female recreational hikers\u003c/em\u003e. Ergonomics, 2012. 55(3): p. 316\u0026ndash;326.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTong, J., et al., \u003cem\u003eEffects of Stature and Load Carriage on the Running Biomechanics of Healthy Men\u003c/em\u003e. IEEE transactions on biomedical engineering, 2023. PP(8): p. 2445\u0026ndash;2453.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWatanabe, K. and Y. Wang, \u003cem\u003eInfluence of Backpack Load and Gait Speed on Plantar Forces During Walking\u003c/em\u003e. Research in sports medicine, 2013. 21(4): p. 395\u0026ndash;401.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHardie, R., et al., \u003cem\u003eThe Effects of Bag Style on Muscle Activity of the Trapezius, Erector Spinae and Latissimus Dorsi During Walking in Female University Students\u003c/em\u003e. Journal of human kinetics, 2015. 45(1): p. 39\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, S.S.W. and D.H.K. Chow, \u003cem\u003eComparison of Predictions Between an EMG-Assisted Approach and Two Optimization-Driven Approaches for Lumbar Spine Loading During Walking With Backpack Loads\u003c/em\u003e. Human factors, 2020. 62(4): p. 565\u0026ndash;577.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSimpson, K.M., B.J. Munro, and J.R. Steele, \u003cem\u003eBackpack load affects lower limb muscle activity patterns of female hikers during prolonged load carriage\u003c/em\u003e. Journal of electromyography and kinesiology, 2011. 21(5): p. 782788.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYali, H., et al., \u003cem\u003eThe muscle activation patterns of lower limb during stair climbing at different backpack load\u003c/em\u003e. Acta of bioengineering and biomechanics, 2015. 17(4): p. 1320.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDames, K.D. and J.D. Smith, \u003cem\u003eEffects of load carriage and footwear on spatiotemporal parameters, kinematics, and metabolic cost of walking\u003c/em\u003e. Gait \u0026amp; posture, 2015. 42(2): p. 122\u0026ndash;126.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRosa, R.G.d., et al., \u003cem\u003eInclined Weight-Loaded Walking at Different Speeds: Pelvis-Shoulder Coordination, Trunk Movements and Cost of Transport\u003c/em\u003e. Journal of motor behavior, 2018. 50(1): p. 73\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbaraogu, U.O., et al., \u003cem\u003eImmediate responses to backpack carriage on postural angles in young adults: A crossover randomized self-controlled study with repeated measures\u003c/em\u003e. Work (Reading, Mass.), 2017. 57(1): p. 87\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLegg, S.J., L. Perko, and P. Campbell, \u003cem\u003eSubjective perceptual methods for comparing backpacks\u003c/em\u003e. Ergonomics, 1997. 40(8): p. 809\u0026ndash;817.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStuempfle, K.J., D.G. Drury, and A.L. Wilson, \u003cem\u003eEffect of load position on physiological and perceptual responses during load carriage with an internal frame backpack\u003c/em\u003e. Ergonomics, 2004. 47(7): p. 784\u0026ndash;789.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChockalingam, N., \u003cem\u003eIntroduction\u003c/em\u003e, in \u003cem\u003eClinical Biomechanics in Human Locomotion\u003c/em\u003e, A. Horwood and N. Chockalingam, Editors. 2023, Academic Press. p. xxiii-xxv.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAttwells, R.L., et al., \u003cem\u003eInfluence of carrying heavy loads on soldiers' posture, movements and gait\u003c/em\u003e. Ergonomics, 2006. 49(14): p. 1527\u0026ndash;1537.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee, J., Y.-J. Yoon, and C.S. Shin, \u003cem\u003eThe Effect of Backpack Load Carriage on the Kinetics and Kinematics of Ankle and Knee Joints During Uphill Walking\u003c/em\u003e. Journal of applied biomechanics, 2017. 33(6): p. 397\u0026ndash;405.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrackley, H.M., J.M. Stevenson, and J.C. Selinger, \u003cem\u003eEffect of backpack load placement on posture and spinal curvature in prepubescent children\u003c/em\u003e. Work (Reading, Mass.), 2009. 32(3): p. 351\u0026ndash;360.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSalavati, M., et al., \u003cem\u003eChanges in postural stability with fatigue of lower extremity frontal and sagittal plane movers\u003c/em\u003e. Gait \u0026amp; Posture, 2007. 26(2): p. 214\u0026ndash;218.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, S.S.W., Y.-P. Zheng, and D.H.K. Chow, \u003cem\u003eChanges of lumbosacral joint compression force profile when walking caused by backpack loads\u003c/em\u003e. Human movement science, 2019. 66: p. 164\u0026ndash;172.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSimpson, K.M., B.J. Munro, and J.R. Steele, \u003cem\u003eEffect of load mass on posture, heart rate and subjective responses of recreational female hikers to prolonged load carriage\u003c/em\u003e. Applied ergonomics, 2011. 42(3): p. 403\u0026ndash;410.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, Y., et al., \u003cem\u003eEffects of Backpack Loads on Leg Muscle Activation during Slope Walking\u003c/em\u003e. Applied sciences, 2020. 10(14): p. 4890.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDevroey, C., et al., \u003cem\u003eEvaluation of the effect of backpack load and position during standing and walking using biomechanical, physiological and subjective measures\u003c/em\u003e. Ergonomics, 2007. 50(5): p. 728\u0026ndash;742.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRen, L., R.K. Jones, and D. Howard, \u003cem\u003eDynamic analysis of load carriage biomechanics during level walking\u003c/em\u003e. Journal of biomechanics, 2005. 38(4): p. 853\u0026ndash;863.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartin, J., et al., \u003cem\u003eEffects of load carriage on measures of postural sway in healthy, young adults: A systematic review and meta-analysis\u003c/em\u003e. Applied Ergonomics, 2023. 106: p. 103893.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoberts, M., et al., \u003cem\u003eChanges in postural sway and gait characteristics as a consequence of anterior load carriage\u003c/em\u003e. Gait \u0026amp; posture, 2018. 66: p. 139\u0026ndash;145.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJamshidi, N., et al., \u003cem\u003eDifferences in center of pressure trajectory between normal and steppage gait\u003c/em\u003e. Journal of research in medical sciences, 2010. 15(1): p. 33\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeglund, N.C., et al., \u003cem\u003eEnergy-saving gait mechanics with head-supported loads\u003c/em\u003e. Nature (London), 1995. 375(6526): p. 52\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMachado, \u0026Aacute;.S., et al., \u003cem\u003eEffects of different hydration supports on stride kinematics, comfort, and impact accelerations during running\u003c/em\u003e. Gait \u0026amp; posture, 2022. 97: p. 115\u0026ndash;121.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeroux, A., J. Fung, and H. Barbeau, \u003cem\u003ePostural adaptation to walking on inclined surfaces: I. Normal strategies\u003c/em\u003e. Gait \u0026amp; Posture, 2002. 15(1): p. 64\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Khabbaz, Y.S.S.M., T. Shimada, and M. Hasegawa, \u003cem\u003eThe effect of backpack heaviness on trunk-lower extremity muscle activities and trunk posture\u003c/em\u003e. Gait \u0026amp; Posture, 2008. 28(2): p. 297\u0026ndash;302.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlexander, N. and H. Schwameder, \u003cem\u003eLower limb joint forces during walking on the level and slopes at different inclinations\u003c/em\u003e. Gait \u0026amp; posture, 2016. 45: p. 137\u0026ndash;142.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLewis, C.L. and S.A. Sahrmann, \u003cem\u003eEffect of posture on hip angles and moments during gait\u003c/em\u003e. Manual Therapy, 2015. 20(1): p. 176\u0026ndash;182.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, S.S.W. and D.H.K. Chow, \u003cem\u003eMulti-objective analysis for assessing simultaneous changes in regional spinal curvatures under backpack carriage in young adults\u003c/em\u003e. Ergonomics, 2016. 59(11): p. 1494\u0026ndash;1504.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHawke, A.L. and R.L. Jensen, \u003cem\u003eAre Trekking Poles Helping or Hindering Your Hiking Experience? A Review\u003c/em\u003e. Wilderness \u0026amp; Environmental Medicine, 2020. 31(4): p. 482\u0026ndash;488.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNandlall, N., et al., \u003cem\u003eThe effect of low back pain and lower limb injury on lumbar multifidus muscle morphology and function in university soccer players\u003c/em\u003e. BMC Musculoskeletal Disorders, 2020. 21(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLaFiandra, M., et al., \u003cem\u003eHow do load carriage and walking speed influence trunk coordination and stride parameters?\u003c/em\u003e Journal of Biomechanics, 2003. 36(1): p. 87\u0026ndash;95.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMorrison, A., J. Hale, and S. Brown, \u003cem\u003eJoint range of motion entropy changes in response to load carriage in military personnel\u003c/em\u003e. Human Movement Science, 2019. 66: p. 249257.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSmith, B., et al., \u003cem\u003eInfluence of carrying a backpack on pelvic tilt, rotation, and obliquity in female college students\u003c/em\u003e. Gait \u0026amp; Posture, 2006. 23(3): p. 263\u0026ndash;267.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSafran, M.R., et al., \u003cem\u003eStrains across the Acetabular Labrum during Hip Motion:A Cadaveric Model\u003c/em\u003e. The American Journal of Sports Medicine, 2011. 39(1_suppl): p. 92\u0026ndash;102.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hiking, Gait, Posture, Backpack","lastPublishedDoi":"10.21203/rs.3.rs-4740002/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4740002/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003eHeavy backpacks are carried by hikers for prolonged walking periods. Backpack designs impact a hiker’s biomechanics.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003eWe assessed the impact of different backpacks on lumbar extension (LE) and centre of pressure (COP) among hikers. Regular hikers (n=8; age = 23.4±1.9, years; weight = 85.1±7.9, kgs; height = 185.3±3.8, cm) who met the eligibility criteria attended testing sessions to test a traditional backpack (TBP) and a balance backpack (BBP), against a no backpack control (NBP) on three different gradient conditions (flat, 0°; incline, 12°; decline, -12°). Walking tests (1.1m/s) were performed on a force plate-embedded treadmill with a surrounding marker-based motion capture system. Multiple separate two-way ANOVA tests assessed the backpack effect on LE and COP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eDunnett’s multiple comparison Post Hoc test revealed significant variance (p \u0026lt; 0.05) for TBP and an insignificant variance for BBP for LE values. A consistent degree of forward trunk lean across all conditions was observed, with a pronounced LE observed when using the TBP. Insignificant variance in the hiker’s COP between the NBP and BBP across all gradients was observed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions:\u003c/strong\u003e This suggests that hikers using a BBP might find their walking posture quite like their normal gait kinematics in comparison to using a TBP.\u003c/p\u003e","manuscriptTitle":" Assessing the Impact of Backpack Design on Hikers Lumbar Extension and Centre of Pressure ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-07 11:41:40","doi":"10.21203/rs.3.rs-4740002/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"13d06dc0-2c3c-490d-9e78-84be44d727a6","owner":[],"postedDate":"August 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-15T04:23:29+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-07 11:41:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4740002","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4740002","identity":"rs-4740002","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}