Effect of functional electrical stimulation on maximum joint angles and gait asymmetry in female athletes post-anterior cruciate ligament reconstruction when crossing obstacles

Effect of functional electrical stimulation on maximum joint angles and gait asymmetry in female athletes post-anterior cruciate ligament reconstruction when crossing obstacles | 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 Effect of functional electrical stimulation on maximum joint angles and gait asymmetry in female athletes post-anterior cruciate ligament reconstruction when crossing obstacles I-Lin Wang, Fei-Fei Lu, Si-Min Lian, Lijuan chang, Yi-Ming Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7128197/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Jan, 2026 Read the published version in BMC Sports Science, Medicine and Rehabilitation → Version 1 posted 12 You are reading this latest preprint version Abstract Background Functional electrical stimulation (FES) can effectively stimulate muscle contraction and has shown great potential in improving human motor function. Female athletes post-anterior cruciate ligament reconstruction (post-ACLR) have pervasive bilateral asymmetries. Moreover, asymmetric gait is often considered one of the risk factors for falls. Methods Twenty female athletes post-ACLR were divided into the FES group and the control (CON) group to cross different obstacle heights (30%, 20%, and 10% of the leg length (LL). The two-way repeated analysis of variance was employed to examine the effects between groups and heights, as well as Bonferroni post-hoc comparison and an independent samples t-test. Results The maximum hip and knee joint angles of the leading and trailing limbs were lower in the FES group than in the CON group (all, P < 0.05). The swing time, gait asymmetry (GA), stance time GA, and swing/stance time GA decreased when crossing obstacles with heights 30% and 20% of the LL (all, P < 0.05). Furthermore, when crossing 30% LL-high obstacles, the step length was shorter in the FES group than in the CON group ( P < 0.05). Conclusions The maximum joint angles of the hip and knee following FES When crossing obstacles with heights 30% and 20% of the LL, the GA between the leading and trailing limbs would be reduced in female athletes owing to their increased lower neuromuscular control ability. Trial registration This trial was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2100053942) on 04/12/2024. Functional electrical stimulation Muscle contraction Cross obstacles Asymmetric gait Gait analysis Lower neuromuscular control Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Background Functional electrical stimulation (FES) has been used for > 60 years and widely recognized by the medical community for its effectiveness in improving the lower limbs and gait in the last 30 years [ 1 ]. Studies have demonstrated that FES can effectively activate the quadriceps muscles, improving lower limb symmetry and optimizing gait patterns in individuals post-anterior cruciate ligament reconstruction (post-ACLR) [ 2 ]. FES involves applying electrical stimulation to elicit muscle contraction, which generates limb movements and supports functional activities. The amount of muscle force generated by FES depends on the number of motor units recruited and the muscle activation rate [ 3 ]. FES mainly involves stimulating neuromuscular tissues with pulsed electrical currents to improve or restore the function of the stimulated muscle or muscle group [ 4 ]. Studies have found that electrical stimulation interventions in the lower limb muscles can induce action potentials in nerve axons. By adjusting the stimulation current to generate varying levels of lower limb muscle contraction, the threshold for the patient’s lower limb motor unit is increased [ 5 , 6 ], enhancing voluntary muscle contraction strength and improving the functional anticipatory activity of the lower limb [ 7 ]. Therefore, FES is employed to induce functional muscle contractions, which enhance muscle strength and improve gait stability. Bilateral asymmetries are common among patients who underwent ACLR during gait and various hop tests and have been closely associated with the incidence of secondary ACL injuries and meniscus pathology [ 8 , 9 ]. Bilateral gait asymmetry (GA) often manifests in gait patterns and is accompanied by imbalances in the lower limb muscle strength, which is a common risk factor for falls during walking [ 10 ]. Bilateral asymmetry is likely to occur when one leg bears more load than the other. Previous studies have shown that the Achilles tendon pressure of the habitual leg is greater than that of the non-habitual leg during gait; however, the load on the uninjured leg is higher than that on the injured leg [ 11 , 12 ]. Consequently, bilateral GA may lead to accidents while walking. Asymmetric gait in the lower limbs can prolong the duration of the gait cycle, worsen the step length difference between the left and right legs, and impair the control of lower limb movements, resulting in decreased gait quality [ 13 ]. Thus, reducing GA can effectively reduce the risk of falls and the occurrence of abnormal posture. Moreover, studies have shown that FES can improve the work efficiency of the lower limb muscles during the support and swing phases of gait, increase the symmetry of the active and antagonistic lower limb muscles, and reduce the co-activation of the antagonistic lower limb muscles when walking. This improvement contributes to the symmetry of the bilateral lower limb gait [ 14 ]. FES can activate the sensorimotor cortex of the brain, enhance the intensity of synaptic transmission, and enable the lower limbs to more accurately judge spatial position and regulate step length [ 15 ]. Therefore, FES may improve lower limb control ability and bilateral asymmetry, resulting in a more stable gait. Crossing obstacles is one of the most common movements in daily and work-related activities; given that movements require maintaining body balance and symmetry to cross obstacles, precise control of the lower limbs is necessary [ 16 ]. Reduced symmetry of the lower limbs during daily walking increases the likelihood of falls. Complex posture symmetry and joint angle adaptation are critical factors affecting gait when crossing obstacles of varying difficulty [ 17 ], with women being at a higher risk of injury in most activities [ 18 ]. FES plays an important role in assisting walking by increasing muscle strength, improving neuromuscular control ability, and promoting symmetry of both lower limbs. However, most studies on the use of FES have focused on barrier-free walking, and limited studies have explored more complex walking tasks. After FES, deep neuromuscular pathways are fully activated, leading to increased muscle strength, as demonstrated by significant differences in outcomes observed in relevant kinematic research. Therefore, this study aimed to investigate the effects of FES on the symmetry and maximum joint angles of both lower limbs for female athletes post-ACLR when crossing obstacles. This study hypothesized that the symmetry of both lower limbs would improve when crossing obstacles with heights 30% and 20% of the leg length (LL) after receiving FES and that the maximum joint angles of the hip and knee would decrease when crossing higher obstacles. Methods Participants Twenty female athletes (aged 22.7 ± 2.5 years; height 166.0 ± 6.4 cm; weight, 58.1 ± 6.2 kg) with ipsilateral hamstring autograft ACLR were recruited 6 months postoperatively through public advertisement. All participants were medically cleared for sports following standardized postoperative rehabilitation, with no concomitant knee pathologies, cognitive impairments, or lower extremity musculoskeletal disorders within 6 months of enrollment. Moreover, a sample size estimation was conducted following a priori power analysis (G*Power version 3.1.9.7; Heinrich Heine University Düsseldorf, Germany). The recommended minimum total sample size was 12 participants, and the sample size met the requirements based on a two-sided significance level of 0.05, statistical power of 0.80, and effect size of 0.77. Participants provided informed consent voluntarily after fully understanding the experimental procedure. All participants used the left and right legs as the leading limb when crossing the obstacle first [ 19 ]. This study was approved by the Human Ethics Committee of Jilin Sport University (JLSU; Changchun, China; JLSU-IRB no. 2021012). Experimental design The study employed a single-blind randomized crossover design, with allocation in two stages. An independent statistician performed computer-generated block randomisation (block size = 4; 5 blocks) using Sealed Envelope ( https://www.sealedenvelope.com ) to assign participants to the FES (n = 10) or CON (n = 10) group. The FES group received FES, and the CON group did not receive any intervention in the first stage. In the second stage, the order of the FES and CON groups was reversed, and the intervention effect was balanced in the two stages. All participants took 7 days off between the two experiments, which were completed within 1 month (Fig. 1 ) [ 10 ]. Thus, the order of the trials was counterbalanced, and the order of crossing the three different LL-high obstacles was randomly assigned [ 20 ]. The investigators and corresponding authors were unblinded to the randomization sequence and intervention assignment. Blinded data from participants were collected at the end of treatment (Table 1 ) [ 21 ]. --- Insert Fig. 1 around here --- Table 1 Blinding data and assessment Guess, n Assignment CON FES DK Total Patient/proxy CON 3 (0%) 3 (1%) 4 (0%) 10 FES 2 (0%) 4 (0%) 4 (0%) 10 Total 5 (0%) 7 (5%) 8 (5%) 20 CON’s BI = 0.04 [95% CI, 0.13–0.27]. FES’s BI = 0.05 [− 0.09 to 0.12]. The functional electrical stimulation was delivered using physiotherapy equipment (SV-ML801 Xinghui Technology, China). In the FES group, the 35 cm 2 rectangular self-adhesive surface electrodes were used to establish electrical contact with the skin [ 22 ]. Bilateral semitendinosus, biceps femoris, rectus femoris, lateral femoris, medial femoris, anterior tibialis, medial gastrocnemius, and lateral gastrocnemius tendons were stimulated with a current intensity of 2 mA for 15 min [ 23 ]. In the CON group, a sham electrode sheet, which did not deliver electrical stimuli, was placed at the same tendon location as in the FES group. This was done to avoid sensory differences between real and sham stimuli perceived by the same participant. All interventions were delivered by licensed physiotherapists with over 5 years of clinical experience. Before each experiment, we ensured that participants performed identical actions in a consistent environment to make sure that they crossed the obstacles correctly. Subsequently, they walked at their preferred pace in a constant-temperature gait laboratory over an obstacle with an adjustable height standardized to 30%, 20%, and 10% of LL of the lower limb leading and trailing legs. Data collection A three-dimensional motion analysis system (Vicon V5, Oxford Metrics Group, UK) containing 10 infrared cameras was used to capture the lower limb motion track at a sampling frequency of 200 Hz, and the three force-measuring plates (AMTI BP600900, USA) collected the ground reaction forces (GRFs) at a sampling frequency of 1200 Hz. Kinematic analyses were conducted, and a fourth-order Butterworth digital filter with cut-off frequencies of 10Hz was used for low-pass filtering of data. Two retroreflective markers were placed at the end of the obstacle. The gait marker set of 19 reflective markers, with a diameter of 14 mm, defined the lower limb model with seven-segment rigid link. The kinetic variables when crossing obstacles with heights 30%, 20% and 10% of the LL in the sagittal planes for each stance phase included the following: (1) hip maximum flexion/extension angles (hip joint), (2) knee maximum flexion/extension angles (knee joint), and (3) ankle maximum flexion/extension angles (ankle joint) of the leading and trailing limbs. The leading limb was defined as the lower limb that first crosses the obstacle, and the trailing limb was the lower limb that crosses the obstacle after the leading limb has crossed the obstacle [ 24 ]. The maximum hip, knee, and ankle joint angles of the left/right leading limb referred to the maximum joint angles during the period from toe-off to the second force plate heel strike (Fig. 2 ) for each trial [ 25 ]. The maximum joint angles of the hip, knee, and ankle of the left/right trailing limb referred to the maximum joint angle of the hip, knee, and ankle during the period from the first force plate toe-off to the third force plate foot heel strike for each trial (Fig. 3 ). The spatiotemporal parameters included stride length (SL), GA, swing time (SW) GA, stance time (ST) GA, swing/ST (SW/ST) GA, and double support (DS) time GA [ 10 ]. --- Insert Fig. 2 – 3 around here --- Statistical analysis Levene’s test was conducted to examine the homogeneity of variance and the Kolmogorov–Smirnov test to determine normality. Missing data were handled using multiple imputation under the missing at random. Descriptive values were obtained and reported as means ± standard deviations. Statistical analysis was performed using MATLAB version R2022a (MathWorks, Inc., Natick, MA, USA). To determine any significant main effects and interactions (2 condition× 3 obstacle height), two-way repeated analysis of variance was employed to compare two group conditions (FES and CON) and three obstacle heights (10%, 20%, and 30% of the LL). If significant interactions exist between the two groups and three heights, the FES and CON groups were independently compared by 10%, 20%, and 30% of the LL using an independent t-test method ( P < 0.05). If no significant interaction occurs, the main effect between groups or heights is analyzed. The significance level was set as P 0.8) [ 26 ]. Results During the intervention period, no participants withdrew from either the FES group or the CON group. The intervention involved 20 participants and was successfully implemented in strict accordance with the CONSORT guidelines, with all assessments completed as planned. In this study, group*height interaction effect showed a significant difference in left/right hip and knee maximum joint angles in the leading and trailing limbs (all, P < 0.05). After FES intervention, the left/right hip and knee maximum joint angles of the leading and trailing limbs were reduced when crossing obstacles with heights 30% and 20% of the LL (all, P < 0.05; ES, 0.07–2.17). Specifically, compared with the CON group, post-hoc comparision analysis revealed that leading left/right hip joint (left, P 30% = 0.001, P 20% < 0.001; right, P 30% = 0.001, P 20% < 0.001) (Fig. 4 c and 4 d), leading left/right knee joint (left, P 30% = 0.008, P 20% = 0.008; right, P 30% < 0.001, P 20% < 0.001) (Fig. 4 e and 4 f), trailing left/right hip joint (left, P 30% < 0.001, P 20% < 0.001; right, P 30% < 0.001, P 20% < 0.001) (Fig. 5 c and 5 d), trailing left/right knee joint (left, P 30% = 0.001, P 20% < 0.001; right, P 30% = 0.001, P 20% = 0.008) (Fig. 5 e and 5 f) of the FES group were reduced when crossing obstacles with heights 30% and 20% of the LL. However, when crossing lower obstacles, such as 10% of the LL, no significant difference was found in the maximum hip, knee, and ankle joint angles between the FES and CON groups (all, P > 0.05). Therefore, FES can induce functional limb movements by properly coordinating and activating muscles and promote safety and has positive implications for preventing falls when crossing higher obstacles in daily life. Gait bilateral asymmetry also showed significant group*height interaction effects on the SL, SW, ST, and SW/ST GA of both lower limbs (all, P < 0.05). FES could reduce the left/right GA when crossing higher obstacles (all, P < 0.05; ES, 0.12–3.71). After FES, the SL GA for both the left ( P 30% < 0.001) and right ( P 30% < 0.001) lower limbs (Fig. 6 a and 7 a) decreased when crossing obstacles with a height 30% of the LL; however, no significant differences in SL GA were observed between the FES and CON group when crossing obstacles with heights 10% and 20% of the LL (all, P > 0.05). In addition, significant differences were found in SW, ST, and SW/ST GA between the FES and CON groups when crossing obstacles with heights 30% and 20% of the LL, except for crossing obstacles with heights 10% of the LL. In particular, the left/right SW GA (left, P 30% < 0.001, P 20% = 0.003; right, P 30% < 0.001, P 20% = 0.048) (Fig. 6 b and 7 b), left/right ST GA (left, P 30% < 0.001, P 20% = 0.029; right, P 30% < 0.001, P 20% < 0.001) (Figs. 6 c and 7 c), left/right SW/ST GA (left, P 30% < 0.001, P 20% < 0.001; right, P 30% < 0.001, P 20% < 0.001) (Figs. 6 e and 7 e) were lower in the FES group than in the CON group. Therefore, gait symmetry increased after FES intervention when crossing more challenging obstacles. --- Insert Fig. 4 – 7 around here --- Discussion This study examined the maximum joint angles and bilateral symmetry of the lower limbs for female athletes post-ACLR while crossing obstacles after FES interventions targeting lower limb muscles. The findings revealed that after stimulation of specific muscle groups of both lower limbs with a current intensity of 2mA for 15 min, the right/left maximum joint angles of the hip and knee on both leading and trailing limbs decreased. Moreover, the right/left SW, ST, and SW/ST GA decreased when crossing obstacles with heights 30% and 20% of the LL. Moreover, the right/left SL GA of the lower limbs decreased when crossing obstacles with heights 30% of the LL. The results were consistent with our research hypothesis, indicating that FES may reduce the risk of falls in female athletes when crossing obstacles. This study showed that the left/right hip and knee maximum joint angles of the leading limb decreased in the FES group compared with those in the CON group when crossing obstacles with heights 30% and 20% of the LL. FES has been employed in various rehabilitation fields to reduce edema, improve or maintain the movements of lower limb joints, prevent muscle atrophy, and increase muscle strength in lower limb muscles [ 27 ]. Associated nerves are activated to stimulate the threshold charge of the muscle fiber action potential, which increases motor evoked potentials and cortical input, thereby influencing the plasticity of motor cortex activity following FES [ 28 ]. Consequently, the muscles that control movement can improve their autonomic contraction after receiving electrical stimulation [ 29 ], allowing the leading limb to execute tasks with reduced hip and knee flexion angles upon receiving the signal, facilitating the formation of a proper gait pattern. In previous studies, FES has been examined for its effects on the knee joint, showing its potential to provide knee feedback control by stimulating lower limb muscles. This results in precise position control of the knee joint, which improves recognition efficiency and control strategies, generating accurate and effective movements [ 30 ]. In this study, FES evoked action potentials during obstacle crossing, which may have increased the strength of lower limb muscles and reduced the ranges of hip and knee joint motions, thereby making it easier to cross obstacles. Furthermore, a study showed that some variables related to crossing lower obstacles may remain unchanged or change insignificantly [ 31 ]. As a result, no difference was found in hip, knee, and ankle joints between the FES and CON groups when the leading limb crossed obstacles with heights 10% of the LL. Moreover, 10% LL-high obstacles are the most common in environments, and the effect of FES is insufficient to alter daily life tasks, particularly those of low difficulty [ 32 ]. This study found no significant differences in ankle joint angles between the FES and CON groups when the leading limb crossed obstacles with heights 30%, 20%, and 10% of the LL. This lack of difference may be attributed to the enhanced control ability of the ankle joint through visual information feedback when crossing obstacles of varying heights. This study revealed that the left/right hip and knee maximum joint angles of the trailing limb decreased in the FES group compared with those in the CON group when crossing obstacles with heights 30% and 20% of the LL. A study reported that FES might activate the muscle fibers of the nerve axon, and the action potential generated in the peripheral motor axon spreads to the muscles [ 33 ]. This allows the muscle to contract harmoniously, improving the functional movement of the lower limb [ 34 ]. Therefore, the trailing limb of the FES group may have increased lower limb muscle strength by enhancing muscle recruitment compared with that of the CON group when crossing higher obstacles (30% and 20% of the LL). In addition, no significant difference in hip and knee joints was noted when the trailing limb crossed 10% LL-high obstacles, and no significant difference in ankle joints was found when the trailing limb crossed obstacles with heights 30%, 20%, and 10% of the LL. Given the low difficulty of movement when crossing lower obstacles, body balance can be maintained through self-control to ensure safe obstacle crossing [ 35 ], which may the lack of difference in the trailing limb’s ankles between the FES and CON groups. Moreover, when crossing 30% LL-high obstacles, the left/right SL GA of the FES group decreased compared with that of the CON group. A study showed that FES may improve gait symmetry by allowing better lower limb gait control [ 36 ]. FES improves neuromuscular control needed to maintain balance, requiring continuous and comprehensive control when walking and crossing obstacles [ 33 ]. Changes in lower limb SL contribute to increased stability between legs, which in turn improves gait quality and reduces the risk of falls [ 37 ]. In this study, the bilateral asymmetry of SL decreased after FES when crossing obstacles with heights > 30% of the LL, which may be due to enhanced leg neuromuscular control ability, making the lower limbs more symmetrical, coordinated, and stable when crossing higher obstacles. However, no significant difference was found in SL GA between the CON and FES groups when crossing obstacles with heights 20% and 10% of the LL. A study did not find a significant difference in SL when crossing lower obstacles under transcranial direct current stimulation, and the gait can be adjusted to adapt to low-level gait patterns [ 10 ]. Therefore, no difference was found in SL GA between the FES and CON groups when crossing lower obstacles. Furthermore, swing and stance gait symmetry are considered key indicators for restoring lower limb function [ 38 ]. Meanwhile, FES helps restore gait symmetry through leg muscle activation to facilitate balance control [ 39 ]. In this study, the lower limb GAs of SW, ST, and SW/ST of FES were reduced compared with those of the CON group when crossing obstacles with heights 30% and 20% of the LL, which may be due to the activation of leg muscles and nerves that stabilize gait, allowing the limbs to complete movements more smoothly and ensuring safety when crossing obstacles. The DS phase refers to the period between the leading limb heel strike and the trailing limb toe-off [ 40 ]. In this study, no difference was noted in SW, ST, and SW/ST GAs between the CON and FES groups when crossing 10% LL-high obstacles, and no difference was noted in DS GA between the CON and FES groups when crossing 20% and 10% LL-high obstacles. Crossing lower obstacles is less challenging, requiring less from the body’s balance and stability control systems, making it easier to complete. Thus, more reliance on external support may be necessary to maintain balance when crossing higher obstacles, allowing the feet to quickly adapt to balance requirements [ 41 ]. Therefore, the lower limbs are in a more stable state during the DS phase and are less affected by external interventions owing to their overall self-control, which means that the SL GA at a height 20% and 10% of the LL is not affected when the FES group crossed lower or medium obstacles. Limitations This study has certain limitations. First, the study was limited to female athletes post-anterior cruciate ligament reconstruction, which may affect the generalizability of the results to other populations. Second, electromyography data were not collected to examine the muscle activation of the lower limbs, limits insight into neuromuscular engagement. Therefore, further study should expand to include diverse populations and exploration of muscle activation during FES in multiple movements is needed to provide a more comprehensive understanding of the effects. Conclusion This study revealed that the maximum joint angles of the hip and knees of the leading and trailing limb decreased, as well as the lower limb GA, after FES among female athletes, who had undergone ACLR, when crossing obstacles with heights 20% and/or 30% of the LL, indicating that FES could increase the symmetry between the leading and trailing limbs, improve the proprioception ability, and reduce the risk of falls. However, FES did not significantly affect outcomes when crossing lower obstacles (10% of the LL), as participants could safely and effectively cross them. Therefore, when crossing higher obstacles after FES, lower limb muscle strength and neuromuscular control ability are increased, which reduces the risk of falls and ensures safe crossing over obstacles. Abbreviations ACLR anterior cruciate ligament reconstruction CON control DS double support ES effect size FES functional electrical stimulation GA gait asymmetry GRF ground reaction force LL leg length ST stance time SW/ST swing/stance time SW swing time Declarations Ethics approval and consent to participate All experimental procedures followed the principles of the Helsinki Declaration and were approved by the Institutional Ethical Committee of Jilin Sport University (JLSU; Changchun, China; JLSU-IRB no. 2021012) and was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2100053942) on 04/12/2024. The participants voluntarily signed the informed consent form after becoming fully aware of the experimental procedure and precautions. Consent for publication Not applicable. Data availability Availability of data and materials All data generated or analyzed during this study are included in this published article. Competing interests The authors declare that there are no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding This work is financially supported by the National Science and Technology Council of Taiwan (grant no. NSTC 114-2320-B-030 -002 -), and partially financially supported by First-class undergraduate professional construction project approve [grant number LPSSYylzy2301]. Authors’ contributions ILW and YMC designed the experiments. YMC, ILW, FFL and SML performed the laboratory experiments. LC, ILW and YMC analyzed the data, interpreted the results, prepared the figures, and wrote the manuscript. ILW, YMC and LC contributed, materials, and analysis platforms. All authors have read and approved the manuscript. Acknowledgements The authors thank all the study participants. References Tan ZM, Liu HH, Yan TB, Jin DM, He XK, Zheng XY, et al. The effectiveness of functional electrical stimulation based on a normal gait pattern on subjects with early stroke: a randomized controlled trial. Biomed Res Int. 2014;2014:545408. Moran U, Gottlieb U, Gam A, Springer S. Functional electrical stimulation following anterior cruciate ligament reconstruction: a randomized controlled pilot study. J Neuroeng Rehabil. 2019;161:89. Schauer T. Sensing motion and muscle activity for feedback control of functional electrical stimulation: ten years of experience in Berlin. Annu Rev Control. 2017;44:355–74. Thrasher TA, Popovic MR. Functional electrical stimulation of walking: function, exercise and rehabilitation. Ann Readapt Med Phys. 2008;516:452–60. Rushton DN. Functional electrical stimulation and rehabilitation—an hypothesis. Med Eng Phys. 2003;251:75–8. Peckham PH, Knutson JS. Functional electrical stimulation for neuromuscular applications. Annu Rev Biomed Eng. 2005;71:327–60. Quandt F, Hummel FC. The influence of functional electrical stimulation on hand motor recovery in stroke patients: a review. Exp Transl Stroke Med. 2014;6:9. Hughes G, Musco P, Caine S, Howe L. Lower limb asymmetry after anterior cruciate ligament reconstruction in adolescent athletes: a systematic review and meta-analysis. J Athl Train. 2020;558:811–25. Alentorn-Geli E, Myer GD, Silvers HJ, Samitier G, Romero D, Lázaro-Haro C, et al. Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 2: a review of prevention programs aimed to modify risk factors and to reduce injury rates. Knee Surg Sports Traumatol Arthrosc. 2009;178:859–79. Wang I-L, Gu C-Y, Lei T-H, Chen C-H, Chiu C-H, Su Y. The effect of transcranial direct current stimulation on bilateral asymmetry and joint angles of the lower limb for females when crossing obstacles. BMC Sports Sci Med Rehabil. 2023;15:176. Bohm S, Mersmann F, Marzilger R, Schroll A, Arampatzis A. Asymmetry of Achilles tendon mechanical and morphological properties between both legs. Scand J Med Sci Sports. 2015;251:e124–32. Speedtsberg MB, Kastoft R, Barfod KW, Penny JØ, Bencke J. Gait Function and Postural Control 4.5 Years After Nonoperative Dynamic Treatment of Acute Achilles Tendon Ruptures. Orthop J Sports Med. 2019;76:2325967119854324. Ito T, Ito Y, Nakai A, Sugiura H, Noritake K, Kidokoro H, et al. Bilateral asymmetry in the gait deviation index in school-aged children with the trait of developmental coordination disorder. Gait Posture. 2021;88:174–9. Park H-K, Jung J, Lee D-W, Shin HC, Lee H-J, Lee W-H. A wearable electromyography-controlled functional electrical stimulation system improves balance, gait function, and symmetry in older adults. Technol Health Care. 2022;302:423–35. Braz GP, Michael R. Functional electrical stimulation control of standing and stepping after spinal cord injury: a review of technical characteristics. Neuromodulation. 2009;123:180–90. Lu T-W, Chen S-C, Chiu H-C. Best-compromise between mechanical energy expenditure and foot clearance predicts leading limb motion during obstacle-crossing. Gait Posture. 2012;363:552–6. Mendez J, Hood S, Gunnel A, Lenzi T. Powered knee and ankle prosthesis with indirect volitional swing control enables level-ground walking and crossing over obstacles. Sci Robot. 2020;544:eaba6635. Capin JJ, Zarzycki R, Ito N, Khandha A, Dix C, Manal K, et al. Gait mechanics in women of the acl-sports randomized control trial: interlimb symmetry improves over time regardless of treatment group. J Orthop Res. 2019;378:1743–53. Begg RK, Sparrow WA, Lythgo ND. Time-domain analysis of foot-ground reaction forces in negotiating obstacles. Gait Posture. 1998;72:99–109. Carda S, Biasiucci A, Maesani A, Ionta S, Moncharmont J, Clarke S et al. Electrically assisted movement therapy in chronic stroke patients with severe upper limb paresis: a pilot, single-blind, randomized crossover study. Arch Phys Med Rehabil. 2017;988:1628-35.e2. Bang H, Flaherty SP, Kolahi J, Park J. Blinding assessment in clinical trials: a review of statistical methods and a proposal of blinding assessment protocol. Clin Res Regul Aff. 2010;272:42–51. Schils S, Ober T. Functional electrical stimulation (FES) in the diagnosis and treatment of musculoskeletal and neuromuscular control abnormalities in horses - selected case studies. J Equine Vet Sci. 2022;117:104078. Coelho-Magalhães T, Azevedo Coste C, Resende-Martins H. A novel functional electrical stimulation-induced cycling controller using reinforcement learning to optimize online muscle activation pattern. Sens (Basel). 2022;2223:9126. Chien-Chung K, Chen S-C, Chen T-Y, Ho T-J, Lin J-G, Lu T-W. Effects of long-term Tai-Chi Chuan practice on whole-body balance control during obstacle-crossing in the elderly. Sci Rep. 2022;121:2660. Yao S, Su Y, Jiang Y-H, Lei T-H, Wang I-L, Hsieh S-L. Increased asymmetry of lower limbs and leading joint angles during crossing obstacles in healthy male with cold exposure. Appl Bionics Biomech. 2022;2022:6421611. Sullivan GM, Feinn R. Using effect size-or why the P value is not enough. J Grad Med Educ. 2012;43:279–82. Lee YJ, Kim KH. The influence of gait training combined with portable functional electrical stimulation on motor function, balance and gait ability in stroke patients. J Back Musculoskelet Rehabil. 2022;356:1171–8. Araki S, Kawada M, Miyazaki T, Nakai Y, Takeshita Y, Matsuzawa Y, et al. Effect of functional electrical stimulation of the gluteus medius during gait in patients following a stroke. Biomed Res Int. 2020;2020:8659845. Rushton DN. Functional electrical stimulation. Physiol Meas. 1997;184:241–75. Previdi F, Carpanzano E. Design of a gain scheduling controller for knee-joint angle control by using functional electrical stimulation. IEEE Trans Control Syst Technol. 2003;113:310–24. Lu TWCS, Chiu HC. Best-compromise between mechanical energy expenditure and foot clearance predicts leading limb motion during obstacle-crossing. Gait Posture. 2012;363:552–6. Wu K-W, Yu C-H, Huang T-H, Lu S-H, Tsai Y-L, Wang T-M, et al. Children with Duchenne muscular dystrophy display specific kinematic strategies during obstacle-crossing. Sci Rep. 2023;131:17094. Enoka RM, Amiridis IG, Duchateau J. Electrical stimulation of muscle: electrophysiology and rehabilitation. Physiol (Bethesda). 2020;351:40–56. Atkins KD, Bickel CS. Effects of functional electrical stimulation on muscle health after spinal cord injury. Curr Opin Pharmacol. 2021;60:226–31. Punt M, Bruijn SM, Wittink H, van de Port IG, Wubbels G, van Dieën JH. Virtual obstacle crossing: reliability and differences in stroke survivors who prospectively experienced falls or no falls. Gait Posture. 2017;58:533–8. Rozanski GM, Huntley AH, Crosby LD, Schinkel-Ivy A, Mansfield A, Patterson KK. Lower limb muscle activity underlying temporal gait asymmetry post-stroke. Clin Neurophysiol. 2020;1318:1848–58. Sabut SK, Sikdar C, Mondal R, Kumar R, Mahadevappa M. Restoration of gait and motor recovery by functional electrical stimulation therapy in persons with stroke. Disabil Rehabil. 2010;3219:1594–603. Plotnik M, Wagner JM, Adusumilli G, Gottlieb A, Naismith RT. Gait asymmetry, and bilateral coordination of gait during a six-minute walk test in persons with multiple sclerosis. Sci Rep. 2020;101:12382. van Bloemendaal M, Bus SA, Nollet F, Geurts ACH, Anita B. Feasibility and preliminary efficacy of gait training assisted by multichannel functional electrical stimulation in early stroke rehabilitation: a pilot randomized controlled trial. Neurorehabil Neural Repair. 2021;352:131–44. Remelius JG, Hamill J, van Emmerik REA. Prospective dynamic balance control during the swing phase of walking: Stability boundaries and time-to-contact analysis. Hum Mov Sci. 2014;36:227–45. Said CM, Goldie PA, Patla AE, Sparrow WA. Effect of stroke on step characteristics of obstacle crossing. Arch Phys Med Rehabil. 2001;8212:1712–9. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 15 Jan, 2026 Read the published version in BMC Sports Science, Medicine and Rehabilitation → Version 1 posted Editorial decision: Revision requested 11 Sep, 2025 Reviews received at journal 19 Aug, 2025 Reviews received at journal 11 Aug, 2025 Reviewers agreed at journal 11 Aug, 2025 Reviews received at journal 09 Aug, 2025 Reviewers agreed at journal 08 Aug, 2025 Reviewers agreed at journal 08 Aug, 2025 Reviewers agreed at journal 06 Aug, 2025 Reviewers invited by journal 06 Aug, 2025 Editor assigned by journal 31 Jul, 2025 Submission checks completed at journal 31 Jul, 2025 First submitted to journal 31 Jul, 2025 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7128197","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":498347690,"identity":"fe8b50ae-5bab-4be2-8d99-2b3ff1e5b910","order_by":0,"name":"I-Lin Wang","email":"","orcid":"","institution":"Liupanshui Normal University","correspondingAuthor":false,"prefix":"","firstName":"I-Lin","middleName":"","lastName":"Wang","suffix":""},{"id":498347691,"identity":"9680de06-067a-4749-a598-d398c455a9da","order_by":1,"name":"Fei-Fei Lu","email":"","orcid":"","institution":"Shenzhen University","correspondingAuthor":false,"prefix":"","firstName":"Fei-Fei","middleName":"","lastName":"Lu","suffix":""},{"id":498347692,"identity":"40567fe9-07ff-4e33-8d29-649dc221c0ad","order_by":2,"name":"Si-Min Lian","email":"","orcid":"","institution":"Jilin Sport University","correspondingAuthor":false,"prefix":"","firstName":"Si-Min","middleName":"","lastName":"Lian","suffix":""},{"id":498347693,"identity":"32e7a6a9-4359-4536-b85b-a6474cb46703","order_by":3,"name":"Lijuan chang","email":"","orcid":"","institution":"Liupanshui Normal University","correspondingAuthor":false,"prefix":"","firstName":"Lijuan","middleName":"","lastName":"chang","suffix":""},{"id":498347694,"identity":"1656a661-aaa5-4b9e-a2e3-459fdaf3ad5a","order_by":4,"name":"Yi-Ming Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/0lEQVRIiWNgGAWjYBACNvnzDww+VNgwMDAzNzBU8IDEEvBr4ZPgYSiccSYNqIWxgeEMTMsBPFrkgFo+87YdBjJBWhiI0MIm3XtwA2/b+Wj+dqCWAzKHGfjZcwyYP7bh0SJzLtlA4tzt3BmHQVp4DjNI9rwxYDiITwtDgpmBQdnt3AagFuYPQC0GN3KAWrbh1WL+I4HtXO58mC32BLVI5BgYHGg7kLsBpsVAgpAWnmMJhg1nknM3ArUcOMCTziNx5lnBgbP/cGuRb28+YPynwi533vnDBx8c7LGW429P3vig4gxuLSjgAGMPAzgyDxCpAQR+kKB2FIyCUTAKRgwAAPouWw0aOWL+AAAAAElFTkSuQmCC","orcid":"","institution":"Fu Jen Catholic University","correspondingAuthor":true,"prefix":"","firstName":"Yi-Ming","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2025-07-15 08:38:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7128197/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7128197/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13102-025-01486-8","type":"published","date":"2026-01-15T16:30:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88786720,"identity":"ceb1ba78-7ac8-4826-b244-798eccad49b0","added_by":"auto","created_at":"2025-08-11 12:01:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":54163,"visible":true,"origin":"","legend":"\u003cp\u003eCONSORT flow diagram.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/3f88c91fbcff772de3f1c56e.png"},{"id":88786714,"identity":"1f53c04f-b569-4b61-8f2c-91274bc6cb8f","added_by":"auto","created_at":"2025-08-11 12:01:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":134040,"visible":true,"origin":"","legend":"\u003cp\u003eFunctional electrical stimulation influences leading limb gait cycle during obstacle crossing in post-ACLR female athletes.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/017b1f568ca3170531855416.png"},{"id":88788099,"identity":"ab44126a-db1f-4b50-b876-41d662418d4b","added_by":"auto","created_at":"2025-08-11 12:09:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":129930,"visible":true,"origin":"","legend":"\u003cp\u003eFunctional electrical stimulation influences trailing limb gait cycle during obstacle crossing in post-ACLR female athletes.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/dfaf92cf27cb923d11932e9a.png"},{"id":88786717,"identity":"9af6a3b5-a411-4b13-9fb2-d29ccd786d9c","added_by":"auto","created_at":"2025-08-11 12:01:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":29487,"visible":true,"origin":"","legend":"\u003cp\u003eFES influences leading limb maximum joint angle during obstacle crossing in post-ACLR female athletes. *A significant interaction effect between the group and height. § The FES group exhibited significant difference from the CON group. †A difference from the 10% leg length (LL) height at each group. ‡A difference from the 20% LL height at each group (P \u0026lt; 0.05) (10%, 20%, and 30% of the LL: crossing obstacle with heights 10%, 20%, and 30% of the LL).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/2d8bf6c21be9a2f8a1c54fc9.png"},{"id":88788100,"identity":"cc67efa3-a56d-47bd-b0e3-cf497f4093b2","added_by":"auto","created_at":"2025-08-11 12:09:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":28737,"visible":true,"origin":"","legend":"\u003cp\u003eFES influences trailing limb maximum joint angle during obstacle crossing in post-ACLR female athletes. *A significant interaction effect between the group and height. § The FES group exhibited significant difference from the CON group. †A difference from the 10% leg length (LL) height at each group. ‡A difference from the 20% LL height at each group (P \u0026lt; 0.05) (10%, 20%, and 30% of the LL: crossing obstacle with heights 10%, 20%, and 30% of the LL).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/7c0d9f4bb381a01a20872547.png"},{"id":88786722,"identity":"24492cb9-6a34-4b24-842c-9d5d828aa43e","added_by":"auto","created_at":"2025-08-11 12:01:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":25684,"visible":true,"origin":"","legend":"\u003cp\u003eFunctional electrical stimulation influences on gait asymmetry during crossing left-sided obstacles in post-ACLR female athletes. *A significant interaction effect between the group and height. §The FES group exhibited significant difference from the CON group. †A difference from the 10% leg length (LL) height at each group. ‡A difference from the 20% LL height at each group (P \u0026lt; 0.05) (10%, 20%, and 30% of the LL: crossing obstacle with heights 10%, 20%, and 30% of the LL).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/98dbea57cc5b22e824f28920.png"},{"id":88786718,"identity":"cbad8bd7-76b2-4857-85fa-066e5164fb50","added_by":"auto","created_at":"2025-08-11 12:01:59","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":27137,"visible":true,"origin":"","legend":"\u003cp\u003eFunctional electrical stimulation influences on gait asymmetry duringright-sided crossing obstacles in post-ACLR female athletes. *A significant interaction effect between the group and height. § The FES group exhibited significant difference from the CON group. †A difference from the 10% leg length (LL) height at each group. ‡A difference from the 20% LL height at each group (P \u0026lt; 0.05) (10%, 20%, and 30% of the LL: crossing obstacle with heights 10%, 20%, and 30% of the LL).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/e782347ed583713917c92203.png"},{"id":100614669,"identity":"d83b2bfd-c019-4c69-b133-7de030785bf8","added_by":"auto","created_at":"2026-01-19 17:23:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1048012,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7128197/v1/02c138a1-05e4-4127-b895-9e1b3daa5ba2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of functional electrical stimulation on maximum joint angles and gait asymmetry in female athletes post-anterior cruciate ligament reconstruction when crossing obstacles","fulltext":[{"header":"Background","content":"\u003cp\u003eFunctional electrical stimulation (FES) has been used for \u0026gt;\u0026thinsp;60 years and widely recognized by the medical community for its effectiveness in improving the lower limbs and gait in the last 30 years [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Studies have demonstrated that FES can effectively activate the quadriceps muscles, improving lower limb symmetry and optimizing gait patterns in individuals post-anterior cruciate ligament reconstruction (post-ACLR) [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. FES involves applying electrical stimulation to elicit muscle contraction, which generates limb movements and supports functional activities. The amount of muscle force generated by FES depends on the number of motor units recruited and the muscle activation rate [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. FES mainly involves stimulating neuromuscular tissues with pulsed electrical currents to improve or restore the function of the stimulated muscle or muscle group [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Studies have found that electrical stimulation interventions in the lower limb muscles can induce action potentials in nerve axons. By adjusting the stimulation current to generate varying levels of lower limb muscle contraction, the threshold for the patient\u0026rsquo;s lower limb motor unit is increased [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], enhancing voluntary muscle contraction strength and improving the functional anticipatory activity of the lower limb [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Therefore, FES is employed to induce functional muscle contractions, which enhance muscle strength and improve gait stability.\u003c/p\u003e\u003cp\u003eBilateral asymmetries are common among patients who underwent ACLR during gait and various hop tests and have been closely associated with the incidence of secondary ACL injuries and meniscus pathology [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Bilateral gait asymmetry (GA) often manifests in gait patterns and is accompanied by imbalances in the lower limb muscle strength, which is a common risk factor for falls during walking [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Bilateral asymmetry is likely to occur when one leg bears more load than the other. Previous studies have shown that the Achilles tendon pressure of the habitual leg is greater than that of the non-habitual leg during gait; however, the load on the uninjured leg is higher than that on the injured leg [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Consequently, bilateral GA may lead to accidents while walking. Asymmetric gait in the lower limbs can prolong the duration of the gait cycle, worsen the step length difference between the left and right legs, and impair the control of lower limb movements, resulting in decreased gait quality [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Thus, reducing GA can effectively reduce the risk of falls and the occurrence of abnormal posture. Moreover, studies have shown that FES can improve the work efficiency of the lower limb muscles during the support and swing phases of gait, increase the symmetry of the active and antagonistic lower limb muscles, and reduce the co-activation of the antagonistic lower limb muscles when walking. This improvement contributes to the symmetry of the bilateral lower limb gait [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. FES can activate the sensorimotor cortex of the brain, enhance the intensity of synaptic transmission, and enable the lower limbs to more accurately judge spatial position and regulate step length [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Therefore, FES may improve lower limb control ability and bilateral asymmetry, resulting in a more stable gait.\u003c/p\u003e\u003cp\u003eCrossing obstacles is one of the most common movements in daily and work-related activities; given that movements require maintaining body balance and symmetry to cross obstacles, precise control of the lower limbs is necessary [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Reduced symmetry of the lower limbs during daily walking increases the likelihood of falls. Complex posture symmetry and joint angle adaptation are critical factors affecting gait when crossing obstacles of varying difficulty [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], with women being at a higher risk of injury in most activities [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. FES plays an important role in assisting walking by increasing muscle strength, improving neuromuscular control ability, and promoting symmetry of both lower limbs. However, most studies on the use of FES have focused on barrier-free walking, and limited studies have explored more complex walking tasks. After FES, deep neuromuscular pathways are fully activated, leading to increased muscle strength, as demonstrated by significant differences in outcomes observed in relevant kinematic research. Therefore, this study aimed to investigate the effects of FES on the symmetry and maximum joint angles of both lower limbs for female athletes post-ACLR when crossing obstacles. This study hypothesized that the symmetry of both lower limbs would improve when crossing obstacles with heights 30% and 20% of the leg length (LL) after receiving FES and that the maximum joint angles of the hip and knee would decrease when crossing higher obstacles.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTwenty female athletes (aged 22.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5 years; height 166.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4 cm; weight, 58.1\u0026thinsp;\u0026plusmn;\u0026thinsp;6.2 kg) with ipsilateral hamstring autograft ACLR were recruited 6 months postoperatively through public advertisement. All participants were medically cleared for sports following standardized postoperative rehabilitation, with no concomitant knee pathologies, cognitive impairments, or lower extremity musculoskeletal disorders within 6 months of enrollment.\u003c/p\u003e\n\u003cp\u003eMoreover, a sample size estimation was conducted following a priori power analysis (G*Power version 3.1.9.7; Heinrich Heine University D\u0026uuml;sseldorf, Germany). The recommended minimum total sample size was 12 participants, and the sample size met the requirements based on a two-sided significance level of 0.05, statistical power of 0.80, and effect size of 0.77.\u003c/p\u003e\n\u003cp\u003eParticipants provided informed consent voluntarily after fully understanding the experimental procedure. All participants used the left and right legs as the leading limb when crossing the obstacle first [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]. This study was approved by the Human Ethics Committee of Jilin Sport University (JLSU; Changchun, China; JLSU-IRB no. 2021012).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExperimental design\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study employed a single-blind randomized crossover design, with allocation in two stages. An independent statistician performed computer-generated block randomisation (block size\u0026thinsp;=\u0026thinsp;4; 5 blocks) using Sealed Envelope (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.sealedenvelope.com\u003c/span\u003e\u003c/span\u003e) to assign participants to the FES (n\u0026thinsp;=\u0026thinsp;10) or CON (n\u0026thinsp;=\u0026thinsp;10) group. The FES group received FES, and the CON group did not receive any intervention in the first stage. In the second stage, the order of the FES and CON groups was reversed, and the intervention effect was balanced in the two stages. All participants took 7 days off between the two experiments, which were completed within 1 month (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]. Thus, the order of the trials was counterbalanced, and the order of crossing the three different LL-high obstacles was randomly assigned [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. The investigators and corresponding authors were unblinded to the randomization sequence and intervention assignment. Blinded data from participants were collected at the end of treatment (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003e--- Insert Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e around here ---\u003c/p\u003e\n\u003ctable id=\"Tab1\" border=\"0\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBlinding data and assessment\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eGuess, n\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAssignment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCON\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFES\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDK\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePatient/proxy\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCON\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3 (1%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFES\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5 (0%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e7 (5%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e8 (5%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n\u003c/table\u003e\n\u003cp\u003eCON\u0026rsquo;s BI\u0026thinsp;=\u0026thinsp;0.04 [95% CI, 0.13\u0026ndash;0.27]. FES\u0026rsquo;s BI\u0026thinsp;=\u0026thinsp;0.05 [\u0026minus;\u0026thinsp;0.09 to 0.12].\u003c/p\u003e\n\u003cp\u003eThe functional electrical stimulation was delivered using physiotherapy equipment (SV-ML801 Xinghui Technology, China). In the FES group, the 35 cm\u003csup\u003e2\u003c/sup\u003e rectangular self-adhesive surface electrodes were used to establish electrical contact with the skin [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. Bilateral semitendinosus, biceps femoris, rectus femoris, lateral femoris, medial femoris, anterior tibialis, medial gastrocnemius, and lateral gastrocnemius tendons were stimulated with a current intensity of 2 mA for 15 min [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. In the CON group, a sham electrode sheet, which did not deliver electrical stimuli, was placed at the same tendon location as in the FES group. This was done to avoid sensory differences between real and sham stimuli perceived by the same participant. All interventions were delivered by licensed physiotherapists with over 5 years of clinical experience. Before each experiment, we ensured that participants performed identical actions in a consistent environment to make sure that they crossed the obstacles correctly. Subsequently, they walked at their preferred pace in a constant-temperature gait laboratory over an obstacle with an adjustable height standardized to 30%, 20%, and 10% of LL of the lower limb leading and trailing legs.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData collection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA three-dimensional motion analysis system (Vicon V5, Oxford Metrics Group, UK) containing 10 infrared cameras was used to capture the lower limb motion track at a sampling frequency of 200 Hz, and the three force-measuring plates (AMTI BP600900, USA) collected the ground reaction forces (GRFs) at a sampling frequency of 1200 Hz. Kinematic analyses were conducted, and a fourth-order Butterworth digital filter with cut-off frequencies of 10Hz was used for low-pass filtering of data. Two retroreflective markers were placed at the end of the obstacle. The gait marker set of 19 reflective markers, with a diameter of 14 mm, defined the lower limb model with seven-segment rigid link. The kinetic variables when crossing obstacles with heights 30%, 20% and 10% of the LL in the sagittal planes for each stance phase included the following: (1) hip maximum flexion/extension angles (hip joint), (2) knee maximum flexion/extension angles (knee joint), and (3) ankle maximum flexion/extension angles (ankle joint) of the leading and trailing limbs.\u003c/p\u003e\n\u003cp\u003eThe leading limb was defined as the lower limb that first crosses the obstacle, and the trailing limb was the lower limb that crosses the obstacle after the leading limb has crossed the obstacle [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]. The maximum hip, knee, and ankle joint angles of the left/right leading limb referred to the maximum joint angles during the period from toe-off to the second force plate heel strike (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) for each trial [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]. The maximum joint angles of the hip, knee, and ankle of the left/right trailing limb referred to the maximum joint angle of the hip, knee, and ankle during the period from the first force plate toe-off to the third force plate foot heel strike for each trial (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). The spatiotemporal parameters included stride length (SL), GA, swing time (SW) GA, stance time (ST) GA, swing/ST (SW/ST) GA, and double support (DS) time GA [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003e--- Insert Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e around here ---\u003c/p\u003e\n\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical analysis\u003c/h2\u003e\n \u003cp\u003eLevene\u0026rsquo;s test was conducted to examine the homogeneity of variance and the Kolmogorov\u0026ndash;Smirnov test to determine normality. Missing data were handled using multiple imputation under the missing at random. Descriptive values were obtained and reported as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations. Statistical analysis was performed using MATLAB version R2022a (MathWorks, Inc., Natick, MA, USA). To determine any significant main effects and interactions (2 condition\u0026times; 3 obstacle height), two-way repeated analysis of variance was employed to compare two group conditions (FES and CON) and three obstacle heights (10%, 20%, and 30% of the LL). If significant interactions exist between the two groups and three heights, the FES and CON groups were independently compared by 10%, 20%, and 30% of the LL using an independent t-test method (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). If no significant interaction occurs, the main effect between groups or heights is analyzed. The significance level was set as \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05. The effect sizes (ES) were measured to verify differences between conditions (small, 0.2; medium, 0.5; large, \u0026gt;\u0026thinsp;0.8) [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eDuring the intervention period, no participants withdrew from either the FES group or the CON group. The intervention involved 20 participants and was successfully implemented in strict accordance with the CONSORT guidelines, with all assessments completed as planned.\u003c/p\u003e\u003cp\u003eIn this study, group*height interaction effect showed a significant difference in left/right hip and knee maximum joint angles in the leading and trailing limbs (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). After FES intervention, the left/right hip and knee maximum joint angles of the leading and trailing limbs were reduced when crossing obstacles with heights 30% and 20% of the LL (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05; ES, 0.07\u0026ndash;2.17). Specifically, compared with the CON group, post-hoc comparision analysis revealed that leading left/right hip joint (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e = 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e = 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed), leading left/right knee joint (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e = 0.008, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e = 0.008; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef), trailing left/right hip joint (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed), trailing left/right knee joint (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e = 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e = 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e = 0.008) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef) of the FES group were reduced when crossing obstacles with heights 30% and 20% of the LL. However, when crossing lower obstacles, such as 10% of the LL, no significant difference was found in the maximum hip, knee, and ankle joint angles between the FES and CON groups (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Therefore, FES can induce functional limb movements by properly coordinating and activating muscles and promote safety and has positive implications for preventing falls when crossing higher obstacles in daily life.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eGait bilateral asymmetry also showed significant group*height interaction effects on the SL, SW, ST, and SW/ST GA of both lower limbs (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). FES could reduce the left/right GA when crossing higher obstacles (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05; ES, 0.12\u0026ndash;3.71). After FES, the SL GA for both the left (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001) and right (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001) lower limbs (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) decreased when crossing obstacles with a height 30% of the LL; however, no significant differences in SL GA were observed between the FES and CON group when crossing obstacles with heights 10% and 20% of the LL (all, \u003cem\u003eP\u0026thinsp;\u0026gt;\u003c/em\u003e\u0026thinsp;0.05). In addition, significant differences were found in SW, ST, and SW/ST GA between the FES and CON groups when crossing obstacles with heights 30% and 20% of the LL, except for crossing obstacles with heights 10% of the LL. In particular, the left/right SW GA (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e = 0.003; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e = 0.048) (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003eb), left/right ST GA (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e = 0.029; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001) (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ec and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ec), left/right SW/ST GA (left, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001; right, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e30%\u003c/sub\u003e \u0026lt; 0.001, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e20%\u003c/sub\u003e \u0026lt; 0.001) (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ee and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003ee) were lower in the FES group than in the CON group. Therefore, gait symmetry increased after FES intervention when crossing more challenging obstacles.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e--- Insert Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e around here ---\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study examined the maximum joint angles and bilateral symmetry of the lower limbs for female athletes post-ACLR while crossing obstacles after FES interventions targeting lower limb muscles. The findings revealed that after stimulation of specific muscle groups of both lower limbs with a current intensity of 2mA for 15 min, the right/left maximum joint angles of the hip and knee on both leading and trailing limbs decreased. Moreover, the right/left SW, ST, and SW/ST GA decreased when crossing obstacles with heights 30% and 20% of the LL. Moreover, the right/left SL GA of the lower limbs decreased when crossing obstacles with heights 30% of the LL. The results were consistent with our research hypothesis, indicating that FES may reduce the risk of falls in female athletes when crossing obstacles.\u003c/p\u003e\u003cp\u003eThis study showed that the left/right hip and knee maximum joint angles of the leading limb decreased in the FES group compared with those in the CON group when crossing obstacles with heights 30% and 20% of the LL. FES has been employed in various rehabilitation fields to reduce edema, improve or maintain the movements of lower limb joints, prevent muscle atrophy, and increase muscle strength in lower limb muscles [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Associated nerves are activated to stimulate the threshold charge of the muscle fiber action potential, which increases motor evoked potentials and cortical input, thereby influencing the plasticity of motor cortex activity following FES [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Consequently, the muscles that control movement can improve their autonomic contraction after receiving electrical stimulation [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], allowing the leading limb to execute tasks with reduced hip and knee flexion angles upon receiving the signal, facilitating the formation of a proper gait pattern. In previous studies, FES has been examined for its effects on the knee joint, showing its potential to provide knee feedback control by stimulating lower limb muscles. This results in precise position control of the knee joint, which improves recognition efficiency and control strategies, generating accurate and effective movements [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In this study, FES evoked action potentials during obstacle crossing, which may have increased the strength of lower limb muscles and reduced the ranges of hip and knee joint motions, thereby making it easier to cross obstacles. Furthermore, a study showed that some variables related to crossing lower obstacles may remain unchanged or change insignificantly [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. As a result, no difference was found in hip, knee, and ankle joints between the FES and CON groups when the leading limb crossed obstacles with heights 10% of the LL. Moreover, 10% LL-high obstacles are the most common in environments, and the effect of FES is insufficient to alter daily life tasks, particularly those of low difficulty [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. This study found no significant differences in ankle joint angles between the FES and CON groups when the leading limb crossed obstacles with heights 30%, 20%, and 10% of the LL. This lack of difference may be attributed to the enhanced control ability of the ankle joint through visual information feedback when crossing obstacles of varying heights.\u003c/p\u003e\u003cp\u003eThis study revealed that the left/right hip and knee maximum joint angles of the trailing limb decreased in the FES group compared with those in the CON group when crossing obstacles with heights 30% and 20% of the LL. A study reported that FES might activate the muscle fibers of the nerve axon, and the action potential generated in the peripheral motor axon spreads to the muscles [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. This allows the muscle to contract harmoniously, improving the functional movement of the lower limb [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Therefore, the trailing limb of the FES group may have increased lower limb muscle strength by enhancing muscle recruitment compared with that of the CON group when crossing higher obstacles (30% and 20% of the LL). In addition, no significant difference in hip and knee joints was noted when the trailing limb crossed 10% LL-high obstacles, and no significant difference in ankle joints was found when the trailing limb crossed obstacles with heights 30%, 20%, and 10% of the LL. Given the low difficulty of movement when crossing lower obstacles, body balance can be maintained through self-control to ensure safe obstacle crossing [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], which may the lack of difference in the trailing limb\u0026rsquo;s ankles between the FES and CON groups.\u003c/p\u003e\u003cp\u003eMoreover, when crossing 30% LL-high obstacles, the left/right SL GA of the FES group decreased compared with that of the CON group. A study showed that FES may improve gait symmetry by allowing better lower limb gait control [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. FES improves neuromuscular control needed to maintain balance, requiring continuous and comprehensive control when walking and crossing obstacles [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Changes in lower limb SL contribute to increased stability between legs, which in turn improves gait quality and reduces the risk of falls [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. In this study, the bilateral asymmetry of SL decreased after FES when crossing obstacles with heights\u0026thinsp;\u0026gt;\u0026thinsp;30% of the LL, which may be due to enhanced leg neuromuscular control ability, making the lower limbs more symmetrical, coordinated, and stable when crossing higher obstacles. However, no significant difference was found in SL GA between the CON and FES groups when crossing obstacles with heights 20% and 10% of the LL. A study did not find a significant difference in SL when crossing lower obstacles under transcranial direct current stimulation, and the gait can be adjusted to adapt to low-level gait patterns [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Therefore, no difference was found in SL GA between the FES and CON groups when crossing lower obstacles. Furthermore, swing and stance gait symmetry are considered key indicators for restoring lower limb function [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Meanwhile, FES helps restore gait symmetry through leg muscle activation to facilitate balance control [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In this study, the lower limb GAs of SW, ST, and SW/ST of FES were reduced compared with those of the CON group when crossing obstacles with heights 30% and 20% of the LL, which may be due to the activation of leg muscles and nerves that stabilize gait, allowing the limbs to complete movements more smoothly and ensuring safety when crossing obstacles. The DS phase refers to the period between the leading limb heel strike and the trailing limb toe-off [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. In this study, no difference was noted in SW, ST, and SW/ST GAs between the CON and FES groups when crossing 10% LL-high obstacles, and no difference was noted in DS GA between the CON and FES groups when crossing 20% and 10% LL-high obstacles. Crossing lower obstacles is less challenging, requiring less from the body\u0026rsquo;s balance and stability control systems, making it easier to complete. Thus, more reliance on external support may be necessary to maintain balance when crossing higher obstacles, allowing the feet to quickly adapt to balance requirements [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Therefore, the lower limbs are in a more stable state during the DS phase and are less affected by external interventions owing to their overall self-control, which means that the SL GA at a height 20% and 10% of the LL is not affected when the FES group crossed lower or medium obstacles.\u003c/p\u003e\u003cp\u003e\u003cb\u003eLimitations\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study has certain limitations. First, the study was limited to female athletes post-anterior cruciate ligament reconstruction, which may affect the generalizability of the results to other populations. Second, electromyography data were not collected to examine the muscle activation of the lower limbs, limits insight into neuromuscular engagement. Therefore, further study should expand to include diverse populations and exploration of muscle activation during FES in multiple movements is needed to provide a more comprehensive understanding of the effects.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study revealed that the maximum joint angles of the hip and knees of the leading and trailing limb decreased, as well as the lower limb GA, after FES among female athletes, who had undergone ACLR, when crossing obstacles with heights 20% and/or 30% of the LL, indicating that FES could increase the symmetry between the leading and trailing limbs, improve the proprioception ability, and reduce the risk of falls. However, FES did not significantly affect outcomes when crossing lower obstacles (10% of the LL), as participants could safely and effectively cross them. Therefore, when crossing higher obstacles after FES, lower limb muscle strength and neuromuscular control ability are increased, which reduces the risk of falls and ensures safe crossing over obstacles.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eACLR\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eanterior cruciate ligament reconstruction\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eCON\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003econtrol\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eDS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003edouble support\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eES\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eeffect size\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eFES\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003efunctional electrical stimulation\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eGA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003egait asymmetry\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eGRF\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eground reaction force\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eLL\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eleg length\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eST\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003estance time\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSW/ST\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eswing/stance time\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSW\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eswing time\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll experimental procedures followed the principles of the Helsinki Declaration and were approved by the Institutional Ethical Committee of Jilin Sport University (JLSU; Changchun, China; JLSU-IRB no. 2021012) and was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2100053942) on 04/12/2024. The participants voluntarily signed the informed consent form after becoming fully aware of the experimental procedure and precautions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work is financially supported by the National Science and Technology Council of Taiwan (grant no. NSTC 114-2320-B-030 -002 -), and partially financially supported by First-class undergraduate professional construction project approve [grant number LPSSYylzy2301].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eILW and YMC designed the experiments. YMC, ILW, FFL and SML performed the laboratory experiments. LC, ILW and YMC analyzed the data, interpreted the results, prepared the figures, and wrote the manuscript. ILW, YMC and LC contributed, materials, and analysis platforms. All authors have read and \u003cstrong\u003eapproved the manuscript.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank all the study participants.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTan ZM, Liu HH, Yan TB, Jin DM, He XK, Zheng XY, et al. The effectiveness of functional electrical stimulation based on a normal gait pattern on subjects with early stroke: a randomized controlled trial. Biomed Res Int. 2014;2014:545408.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMoran U, Gottlieb U, Gam A, Springer S. Functional electrical stimulation following anterior cruciate ligament reconstruction: a randomized controlled pilot study. J Neuroeng Rehabil. 2019;161:89.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchauer T. Sensing motion and muscle activity for feedback control of functional electrical stimulation: ten years of experience in Berlin. Annu Rev Control. 2017;44:355\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eThrasher TA, Popovic MR. Functional electrical stimulation of walking: function, exercise and rehabilitation. Ann Readapt Med Phys. 2008;516:452\u0026ndash;60.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRushton DN. Functional electrical stimulation and rehabilitation\u0026mdash;an hypothesis. Med Eng Phys. 2003;251:75\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePeckham PH, Knutson JS. Functional electrical stimulation for neuromuscular applications. Annu Rev Biomed Eng. 2005;71:327\u0026ndash;60.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eQuandt F, Hummel FC. The influence of functional electrical stimulation on hand motor recovery in stroke patients: a review. Exp Transl Stroke Med. 2014;6:9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHughes G, Musco P, Caine S, Howe L. Lower limb asymmetry after anterior cruciate ligament reconstruction in adolescent athletes: a systematic review and meta-analysis. J Athl Train. 2020;558:811\u0026ndash;25.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlentorn-Geli E, Myer GD, Silvers HJ, Samitier G, Romero D, L\u0026aacute;zaro-Haro C, et al. Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 2: a review of prevention programs aimed to modify risk factors and to reduce injury rates. Knee Surg Sports Traumatol Arthrosc. 2009;178:859\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang I-L, Gu C-Y, Lei T-H, Chen C-H, Chiu C-H, Su Y. The effect of transcranial direct current stimulation on bilateral asymmetry and joint angles of the lower limb for females when crossing obstacles. BMC Sports Sci Med Rehabil. 2023;15:176.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBohm S, Mersmann F, Marzilger R, Schroll A, Arampatzis A. Asymmetry of Achilles tendon mechanical and morphological properties between both legs. Scand J Med Sci Sports. 2015;251:e124\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpeedtsberg MB, Kastoft R, Barfod KW, Penny J\u0026Oslash;, Bencke J. Gait Function and Postural Control 4.5 Years After Nonoperative Dynamic Treatment of Acute Achilles Tendon Ruptures. Orthop J Sports Med. 2019;76:2325967119854324.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eIto T, Ito Y, Nakai A, Sugiura H, Noritake K, Kidokoro H, et al. Bilateral asymmetry in the gait deviation index in school-aged children with the trait of developmental coordination disorder. Gait Posture. 2021;88:174\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePark H-K, Jung J, Lee D-W, Shin HC, Lee H-J, Lee W-H. A wearable electromyography-controlled functional electrical stimulation system improves balance, gait function, and symmetry in older adults. Technol Health Care. 2022;302:423\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBraz GP, Michael R. Functional electrical stimulation control of standing and stepping after spinal cord injury: a review of technical characteristics. Neuromodulation. 2009;123:180\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu T-W, Chen S-C, Chiu H-C. Best-compromise between mechanical energy expenditure and foot clearance predicts leading limb motion during obstacle-crossing. Gait Posture. 2012;363:552\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMendez J, Hood S, Gunnel A, Lenzi T. Powered knee and ankle prosthesis with indirect volitional swing control enables level-ground walking and crossing over obstacles. Sci Robot. 2020;544:eaba6635.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCapin JJ, Zarzycki R, Ito N, Khandha A, Dix C, Manal K, et al. Gait mechanics in women of the acl-sports randomized control trial: interlimb symmetry improves over time regardless of treatment group. J Orthop Res. 2019;378:1743\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBegg RK, Sparrow WA, Lythgo ND. Time-domain analysis of foot-ground reaction forces in negotiating obstacles. Gait Posture. 1998;72:99\u0026ndash;109.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCarda S, Biasiucci A, Maesani A, Ionta S, Moncharmont J, Clarke S et al. Electrically assisted movement therapy in chronic stroke patients with severe upper limb paresis: a pilot, single-blind, randomized crossover study. Arch Phys Med Rehabil. 2017;988:1628-35.e2.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBang H, Flaherty SP, Kolahi J, Park J. Blinding assessment in clinical trials: a review of statistical methods and a proposal of blinding assessment protocol. Clin Res Regul Aff. 2010;272:42\u0026ndash;51.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchils S, Ober T. Functional electrical stimulation (FES) in the diagnosis and treatment of musculoskeletal and neuromuscular control abnormalities in horses - selected case studies. J Equine Vet Sci. 2022;117:104078.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCoelho-Magalh\u0026atilde;es T, Azevedo Coste C, Resende-Martins H. A novel functional electrical stimulation-induced cycling controller using reinforcement learning to optimize online muscle activation pattern. Sens (Basel). 2022;2223:9126.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChien-Chung K, Chen S-C, Chen T-Y, Ho T-J, Lin J-G, Lu T-W. Effects of long-term Tai-Chi Chuan practice on whole-body balance control during obstacle-crossing in the elderly. Sci Rep. 2022;121:2660.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYao S, Su Y, Jiang Y-H, Lei T-H, Wang I-L, Hsieh S-L. Increased asymmetry of lower limbs and leading joint angles during crossing obstacles in healthy male with cold exposure. Appl Bionics Biomech. 2022;2022:6421611.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSullivan GM, Feinn R. Using effect size-or why the P value is not enough. J Grad Med Educ. 2012;43:279\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLee YJ, Kim KH. The influence of gait training combined with portable functional electrical stimulation on motor function, balance and gait ability in stroke patients. J Back Musculoskelet Rehabil. 2022;356:1171\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAraki S, Kawada M, Miyazaki T, Nakai Y, Takeshita Y, Matsuzawa Y, et al. Effect of functional electrical stimulation of the gluteus medius during gait in patients following a stroke. Biomed Res Int. 2020;2020:8659845.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRushton DN. Functional electrical stimulation. Physiol Meas. 1997;184:241\u0026ndash;75.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePrevidi F, Carpanzano E. Design of a gain scheduling controller for knee-joint angle control by using functional electrical stimulation. IEEE Trans Control Syst Technol. 2003;113:310\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu TWCS, Chiu HC. Best-compromise between mechanical energy expenditure and foot clearance predicts leading limb motion during obstacle-crossing. Gait Posture. 2012;363:552\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWu K-W, Yu C-H, Huang T-H, Lu S-H, Tsai Y-L, Wang T-M, et al. Children with Duchenne muscular dystrophy display specific kinematic strategies during obstacle-crossing. Sci Rep. 2023;131:17094.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEnoka RM, Amiridis IG, Duchateau J. Electrical stimulation of muscle: electrophysiology and rehabilitation. Physiol (Bethesda). 2020;351:40\u0026ndash;56.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAtkins KD, Bickel CS. Effects of functional electrical stimulation on muscle health after spinal cord injury. Curr Opin Pharmacol. 2021;60:226\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePunt M, Bruijn SM, Wittink H, van de Port IG, Wubbels G, van Die\u0026euml;n JH. Virtual obstacle crossing: reliability and differences in stroke survivors who prospectively experienced falls or no falls. Gait Posture. 2017;58:533\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRozanski GM, Huntley AH, Crosby LD, Schinkel-Ivy A, Mansfield A, Patterson KK. Lower limb muscle activity underlying temporal gait asymmetry post-stroke. Clin Neurophysiol. 2020;1318:1848\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSabut SK, Sikdar C, Mondal R, Kumar R, Mahadevappa M. Restoration of gait and motor recovery by functional electrical stimulation therapy in persons with stroke. Disabil Rehabil. 2010;3219:1594\u0026ndash;603.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePlotnik M, Wagner JM, Adusumilli G, Gottlieb A, Naismith RT. Gait asymmetry, and bilateral coordination of gait during a six-minute walk test in persons with multiple sclerosis. Sci Rep. 2020;101:12382.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003evan Bloemendaal M, Bus SA, Nollet F, Geurts ACH, Anita B. Feasibility and preliminary efficacy of gait training assisted by multichannel functional electrical stimulation in early stroke rehabilitation: a pilot randomized controlled trial. Neurorehabil Neural Repair. 2021;352:131\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRemelius JG, Hamill J, van Emmerik REA. Prospective dynamic balance control during the swing phase of walking: Stability boundaries and time-to-contact analysis. Hum Mov Sci. 2014;36:227\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSaid CM, Goldie PA, Patla AE, Sparrow WA. Effect of stroke on step characteristics of obstacle crossing. Arch Phys Med Rehabil. 2001;8212:1712\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Functional electrical stimulation, Muscle contraction, Cross obstacles, Asymmetric gait, Gait analysis, Lower neuromuscular control","lastPublishedDoi":"10.21203/rs.3.rs-7128197/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7128197/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eFunctional electrical stimulation (FES) can effectively stimulate muscle contraction and has shown great potential in improving human motor function. Female athletes post-anterior cruciate ligament reconstruction (post-ACLR) have pervasive bilateral asymmetries. Moreover, asymmetric gait is often considered one of the risk factors for falls.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eTwenty female athletes post-ACLR were divided into the FES group and the control (CON) group to cross different obstacle heights (30%, 20%, and 10% of the leg length (LL). The two-way repeated analysis of variance was employed to examine the effects between groups and heights, as well as Bonferroni post-hoc comparison and an independent samples t-test.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe maximum hip and knee joint angles of the leading and trailing limbs were lower in the FES group than in the CON group (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The swing time, gait asymmetry (GA), stance time GA, and swing/stance time GA decreased when crossing obstacles with heights 30% and 20% of the LL (all, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Furthermore, when crossing 30% LL-high obstacles, the step length was shorter in the FES group than in the CON group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eThe maximum joint angles of the hip and knee following FES When crossing obstacles with heights 30% and 20% of the LL, the GA between the leading and trailing limbs would be reduced in female athletes owing to their increased lower neuromuscular control ability.\u003c/p\u003e\u003ch2\u003eTrial registration\u003c/h2\u003e\u003cp\u003eThis trial was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2100053942) on 04/12/2024.\u003c/p\u003e","manuscriptTitle":"Effect of functional electrical stimulation on maximum joint angles and gait asymmetry in female athletes post-anterior cruciate ligament reconstruction when crossing obstacles","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-11 12:01:54","doi":"10.21203/rs.3.rs-7128197/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-11T06:29:29+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-20T00:23:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-11T16:01:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"245380405674804724680858114780922463460","date":"2025-08-11T07:22:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-09T21:56:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"174741131937566228195714450943253821940","date":"2025-08-08T07:03:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"112009405412367214247140884152062895053","date":"2025-08-08T06:42:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"256856845400276108380091968893359554116","date":"2025-08-06T12:21:47+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-06T07:05:13+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-31T14:09:25+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-31T08:50:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2025-07-31T08:19:25+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a55a9d73-f5fb-418c-bf15-c44be47d01f3","owner":[],"postedDate":"August 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T16:47:08+00:00","versionOfRecord":{"articleIdentity":"rs-7128197","link":"https://doi.org/10.1186/s13102-025-01486-8","journal":{"identity":"bmc-sports-science-medicine-and-rehabilitation","isVorOnly":false,"title":"BMC Sports Science, Medicine and Rehabilitation"},"publishedOn":"2026-01-15 16:30:00","publishedOnDateReadable":"January 15th, 2026"},"versionCreatedAt":"2025-08-11 12:01:54","video":"","vorDoi":"10.1186/s13102-025-01486-8","vorDoiUrl":"https://doi.org/10.1186/s13102-025-01486-8","workflowStages":[]},"version":"v1","identity":"rs-7128197","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7128197","identity":"rs-7128197","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}