{"title":"Authors’ response to the Letter to the Editor regarding “The passive stretching response of the human biceps femoris long head muscle varies regionally”","authors":"Ginji Nara , Gakuto Nakao , Adam Kositsky , Keigo Taniguchi","doi":"10.1016/j.jbiomech.2025.113122","DOIUrl":"10.1016/j.jbiomech.2025.113122","url":null,"abstract":"","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113122"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145793617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cerebrovascular dysfunction is associated with aging and the progression of neurodegenerative diseases. Optical coherence elastography (OCE) is an emerging technique for measuring the stiffness of arteries nondestructively with high spatial resolution. In this study, we employed wave-based OCE to measure the shear modulus of human anterior cerebral arteries (ACA). Surface elastic waves were excited on ACA across a wide frequency range (2 to 100 kHz), at intra-vessel pressures ranging from 20 to 140 mmHg. Lamb wave theory was applied to analyze the propagation speeds of dispersive elastic waves guided along the arterial walls and determine shear modulus. The measured shear modulus increases linearly with pressure, reflecting the hyper-elastic properties of arterial walls. The data were compared with stiffness values derived from conventional biaxial extension-inflation mechanical testing. The shear modulus determined from high frequency OCE measurements are much higher when compared to those from the quasi-static mechanical tests. Nevertheless, both measurements demonstrated a consistent trend of cerebral artery stiffening with aging.
{"title":"Nondestructive measurement of anterior cerebral artery stiffness using optical coherence elastography","authors":"Mykyta Ananchenko , Xu Feng , Samuel Halvorsen , Seok-Hyun Yun , Yanhang Zhang","doi":"10.1016/j.jbiomech.2026.113147","DOIUrl":"10.1016/j.jbiomech.2026.113147","url":null,"abstract":"<div><div>Cerebrovascular dysfunction is associated with aging and the progression of neurodegenerative diseases. Optical coherence elastography (OCE) is an emerging technique for measuring the stiffness of arteries nondestructively with high spatial resolution. In this study, we employed wave-based OCE to measure the shear modulus of human anterior cerebral arteries (ACA). Surface elastic waves were excited on ACA across a wide frequency range (2 to 100 kHz), at intra-vessel pressures ranging from 20 to 140 mmHg. Lamb wave theory was applied to analyze the propagation speeds of dispersive elastic waves guided along the arterial walls and determine shear modulus. The measured shear modulus increases linearly with pressure, reflecting the hyper-elastic properties of arterial walls. The data were compared with stiffness values derived from conventional biaxial extension-inflation mechanical testing. The shear modulus determined from high frequency OCE measurements are much higher when compared to those from the quasi-static mechanical tests. Nevertheless, both measurements demonstrated a consistent trend of cerebral artery stiffening with aging.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113147"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145966171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-12-11DOI: 10.1016/j.jbiomech.2025.113125
Pavlos E. Evangelidis , Yasuo Kawakami
{"title":"Letter to the Editor regarding “The passive stretching response of the human biceps femoris long head muscle varies regionally.” by Nara et al.","authors":"Pavlos E. Evangelidis , Yasuo Kawakami","doi":"10.1016/j.jbiomech.2025.113125","DOIUrl":"10.1016/j.jbiomech.2025.113125","url":null,"abstract":"","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113125"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145756836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-12-13DOI: 10.1016/j.jbiomech.2025.113127
Shayne Vial , Jodie Cochrane Wilkie , Anthony J. Blazevich , Daniel Kadlec
Non-contact hamstring injuries (HSIs) commonly occur during the late swing phase of sprinting, when muscle–tendon units (MTUs) approach maximum length. Although sagittal-plane pelvis, hip and knee angles are often used as surrogate measures of overall hamstring lengthening, their predictive validity remains uncertain. This study investigated whether peak three-dimensional lower limb joint angles predict length change in the biarticular hamstring MTUs from peak hip flexion through to toe off (0–100 %) in fourteen intermediate-level male soccer players sprinting at maximal speed (8.56 ± 0.47 m·s−1). Participant-specific musculoskeletal models were used to compute MTU lengths for the biceps femoris long head (BFlh), semimembranosus (SM), and semitendinosus (ST). To account for inter-subject temporal variability and enable accurate point-to-point comparisons across trials, dynamic time warping was applied for non-linear temporal registration. Statistical parametric mapping regression was used to assess associations between pelvis, hip and knee peak joint angles (sagittal, frontal, transverse) and length change of BFlh, SM, and ST. Peak sagittal angles were poor predictors while peak frontal pelvis angle was negatively associated with MTU length change during late swing (BFlh peak |r| = −0.371; SM peak |r| = −0.460). Frontal hip adduction was negatively associated with MTU length change from peak hip flexion to early stance (peak |r| −0.39 to −0.46). Internal hip rotation was associated with SM and ST lengthening (peak |r| = 0.51) from late swing to early stance. Knee extension angles showed no significant associations. These findings suggest caution when using single-plane joint angles as isolated indicators of hamstring MTU length.
{"title":"Peak lower limb joint angles are weak predictors of hamstring length change during sprinting","authors":"Shayne Vial , Jodie Cochrane Wilkie , Anthony J. Blazevich , Daniel Kadlec","doi":"10.1016/j.jbiomech.2025.113127","DOIUrl":"10.1016/j.jbiomech.2025.113127","url":null,"abstract":"<div><div>Non-contact hamstring injuries (HSIs) commonly occur during the late swing phase of sprinting, when muscle–tendon units (MTUs) approach maximum length. Although sagittal-plane pelvis, hip and knee angles are often used as surrogate measures of overall hamstring lengthening, their predictive validity remains uncertain. This study investigated whether peak three-dimensional lower limb joint angles predict length change in the biarticular hamstring MTUs from peak hip flexion through to toe off (0–100 %) in fourteen intermediate-level male soccer players sprinting at maximal speed (8.56 ± 0.47 m·s<sup>−1</sup>). Participant-specific musculoskeletal models were used to compute MTU lengths for the biceps femoris long head (BFlh), semimembranosus (SM), and semitendinosus (ST). To account for inter-subject temporal variability and enable accurate point-to-point comparisons across trials, dynamic time warping was applied for non-linear temporal registration. Statistical parametric mapping regression was used to assess associations between pelvis, hip and knee peak joint angles (sagittal, frontal, transverse) and length change of BFlh, SM, and ST. Peak sagittal angles were poor predictors while peak frontal pelvis angle was negatively associated with MTU length change during late swing (BFlh peak |r| = −0.371; SM peak |r| = −0.460). Frontal hip adduction was negatively associated with MTU length change from peak hip flexion to early stance (peak |r| −0.39 to −0.46). Internal hip rotation was associated with SM and ST lengthening (peak |r| = 0.51) from late swing to early stance. Knee extension angles showed no significant associations. These findings suggest caution when using single-plane joint angles as isolated indicators of hamstring MTU length.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113127"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-12-13DOI: 10.1016/j.jbiomech.2025.113111
Marco Hagen , Matthias Lahner , Nina Lahner
{"title":"Corrigendum to “Machine-based subtalar pronator and supinator strength training increases rearfoot stability in male runners” [J. Biomech. 187 (2025) 112770]","authors":"Marco Hagen , Matthias Lahner , Nina Lahner","doi":"10.1016/j.jbiomech.2025.113111","DOIUrl":"10.1016/j.jbiomech.2025.113111","url":null,"abstract":"","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113111"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145756826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-12-26DOI: 10.1016/j.jbiomech.2025.113141
Rachael Principato, K.Josh Briar, Stephen H.M. Brown
Studies of skeletal muscle fibre function often incorporate stiffness tests to provide information on contractile performance. These tests are most often performed by applying rapid small (<0.5 % fibre length) lengthening or shortening steps and measuring the corresponding change in force. Despite these stiffness tests being regularly performed in studies of contractile function, their repeatability during contractions has not been evaluated, and reported differences in stiffness measured from lengthening versus shortening tests have not been fully evaluated. Single muscle fibres were chemically permeabilized and maximally activated at three different lengths. During maximal activation at each length three lengthening and three shortening tests were performed; these were then repeated with the fibre relaxed. Both stiffness and force measures were normalized to fibre size (stiffness normalized to modulus and force normalized to stress (i.e. specific force)) to best represent the intrinsic properties of the fibres. Active modulus tests were highly repeatable with mean coefficient of variations (CoV) less than 0.028 (2.8 %). Active modulus was on average 28 % higher in all fibres in response to the lengthening compared to the shortening tests. Interestingly, correlations between specific force and active modulus were significantly (p < 0.01) higher for the shortening (r = 0.86) compared to lengthening (r = 0.78) tests. Relaxed modulus tests were less repeatable with mean CoVs ranging from 0.089 to 0.151 (8.9 to 15.1 %). Relaxed modulus was not significantly affected by the direction (lengthening versus shortening) of the test.
{"title":"Comparison of lengthening and shortening stiffness tests in single skeletal muscle fibres","authors":"Rachael Principato, K.Josh Briar, Stephen H.M. Brown","doi":"10.1016/j.jbiomech.2025.113141","DOIUrl":"10.1016/j.jbiomech.2025.113141","url":null,"abstract":"<div><div>Studies of skeletal muscle fibre function often incorporate stiffness tests to provide information on contractile performance. These tests are most often performed by applying rapid small (<0.5 % fibre length) lengthening or shortening steps and measuring the corresponding change in force. Despite these stiffness tests being regularly performed in studies of contractile function, their repeatability during contractions has not been evaluated, and reported differences in stiffness measured from lengthening versus shortening tests have not been fully evaluated. Single muscle fibres were chemically permeabilized and maximally activated at three different lengths. During maximal activation at each length three lengthening and three shortening tests were performed; these were then repeated with the fibre relaxed. Both stiffness and force measures were normalized to fibre size (stiffness normalized to modulus and force normalized to stress (i.e. specific force)) to best represent the intrinsic properties of the fibres. Active modulus tests were highly repeatable with mean coefficient of variations (CoV) less than 0.028 (2.8 %). Active modulus was on average 28 % higher in all fibres in response to the lengthening compared to the shortening tests. Interestingly, correlations between specific force and active modulus were significantly (p < 0.01) higher for the shortening (r = 0.86) compared to lengthening (r = 0.78) tests. Relaxed modulus tests were less repeatable with mean CoVs ranging from 0.089 to 0.151 (8.9 to 15.1 %). Relaxed modulus was not significantly affected by the direction (lengthening versus shortening) of the test.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"196 ","pages":"Article 113141"},"PeriodicalIF":2.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145908670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cortical bone, prominently found in the diaphyseal region of long bones, can resist higher ultimate stresses than trabecular bone and serves as the primary load-bearing compartment of the skeleton. The importance of cortical bone in determining mechanical strength and assessing fracture risk has been highlighted in both experimental and computational studies, motivating the need for better understanding through large-scale analysis. To support large data processing, an automated technique for measuring cortical thickness from clinical CT scans with sub-millimetre accuracy was introduced by Treece et al. (2012). However, this method struggles to reconstruct and calculate cortical bone thickness across diverse long bone morphologies. In this study, we present an adapted version of the technique with improved robustness. When the 2012 published method is evaluated on 240 long bones across six types, it resulted in failures across all test cases, with mean failure rates of 2.9%, 8.0%, 10.5%, 13.7%, 17.9%, and 24.8% in humerus, femur, radius, ulna, tibia and fibula, respectively. In contrast, the proposed new method eliminated failures in all bones except for the fibula, where 9 out of 40 test cases failed with a reduced mean failure rate of 1.9%. These results demonstrate that the new method broadens the applicability of the previous approach by robustly handling morphological variation, making it more suitable for large-scale studies. We anticipate the proposed workflow will serve as a valuable resource for analysing datasets with population-level variability and improving our understanding of osteogenic phenomena in clinically meaningful contexts.
{"title":"Robust workflow for diaphyseal cortical bone thickness calculation","authors":"Julie Kim , Ted Yeung , Roshni Raghvani , Julie Choisne , Thor Besier","doi":"10.1016/j.jbiomech.2025.113034","DOIUrl":"10.1016/j.jbiomech.2025.113034","url":null,"abstract":"<div><div>Cortical bone, prominently found in the diaphyseal region of long bones, can resist higher ultimate stresses than trabecular bone and serves as the primary load-bearing compartment of the skeleton. The importance of cortical bone in determining mechanical strength and assessing fracture risk has been highlighted in both experimental and computational studies, motivating the need for better understanding through large-scale analysis. To support large data processing, an automated technique for measuring cortical thickness from clinical CT scans with sub-millimetre accuracy was introduced by Treece et al. (2012). However, this method struggles to reconstruct and calculate cortical bone thickness across diverse long bone morphologies. In this study, we present an adapted version of the technique with improved robustness. When the 2012 published method is evaluated on 240 long bones across six types, it resulted in failures across all test cases, with mean failure rates of 2.9%, 8.0%, 10.5%, 13.7%, 17.9%, and 24.8% in humerus, femur, radius, ulna, tibia and fibula, respectively. In contrast, the proposed new method eliminated failures in all bones except for the fibula, where 9 out of 40 test cases failed with a reduced mean failure rate of 1.9%. These results demonstrate that the new method broadens the applicability of the previous approach by robustly handling morphological variation, making it more suitable for large-scale studies. We anticipate the proposed workflow will serve as a valuable resource for analysing datasets with population-level variability and improving our understanding of osteogenic phenomena in clinically meaningful contexts.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"194 ","pages":"Article 113034"},"PeriodicalIF":2.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145564083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Femoral loading conditions are key in biomechanical analysis and prediction of fracture risk in children. Biomechanical assessment may be particularly useful in children with bone fragility disorders who may have greater risk of fracture during early developmental stages of mobility. However, a complete characterization of femoral loading during this early stage of walking has not been previously reported. Our primary goal was to develop regression models to characterize femoral loading at the hip during gait in newly walking children. Gait and kinetic analyses were conducted for children aged 13–23 months to obtain hip joint loading during walking experiments. 3D hip joint reaction forces and moments were determined. Regression models were developed to predict peak hip loading using subject characteristics and walking speed as factors. 16 gait cycles from 5 subjects were analyzed. Mean peak resultant hip force was 1.19 N/BW (0.22 SD, normalized by body weight, BW) and the corresponding mean peak resultant hip moment was 0.24 Nm/(BWxL) (0.08 SD, normalized by BW, and leg length, L). Predictive models for resultant hip force and hip moment based on age, height, and walking speed yielded R2 values of 0.97 and 0.94, respectively. Hip joint loading in newly walking children was experimentally determined and predictive models of peak hip loading in gait were described for these children. Regression models predicting subject-specific peak hip joint loading can be applied in future applications such as subject-specific fracture risk assessments using finite element analysis without having to conduct gait experiments.
{"title":"Femur loading during gait in newly walking children","authors":"Keyonna McKinsey , Angela Thompson , Gina Bertocci","doi":"10.1016/j.jbiomech.2025.113069","DOIUrl":"10.1016/j.jbiomech.2025.113069","url":null,"abstract":"<div><div>Femoral loading conditions are key in biomechanical analysis and prediction of fracture risk in children. Biomechanical assessment may be particularly useful in children with bone fragility disorders who may have greater risk of fracture during early developmental stages of mobility. However, a complete characterization of femoral loading during this early stage of walking has not been previously reported. Our primary goal was to develop regression models to characterize femoral loading at the hip during gait in newly walking children. Gait and kinetic analyses were conducted for children aged 13–23 months to obtain hip joint loading during walking experiments. 3D hip joint reaction forces and moments were determined. Regression models were developed to predict peak hip loading using subject characteristics and walking speed as factors. 16 gait cycles from 5 subjects were analyzed. Mean peak resultant hip force was 1.19 N/BW (0.22 SD, normalized by body weight, BW) and the corresponding mean peak resultant hip moment was 0.24 Nm/(BWxL) (0.08 SD, normalized by BW, and leg length, L). Predictive models for resultant hip force and hip moment based on age, height, and walking speed yielded R<sup>2</sup> values of 0.97 and 0.94, respectively. Hip joint loading in newly walking children was experimentally determined and predictive models of peak hip loading in gait were described for these children. Regression models predicting subject-specific peak hip joint loading can be applied in future applications such as subject-specific fracture risk assessments using finite element analysis without having to conduct gait experiments.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"194 ","pages":"Article 113069"},"PeriodicalIF":2.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145564065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-12-15DOI: 10.1016/j.jbiomech.2025.113135
Hanjun Park , Maury A. Nussbaum
Occupational arm-support exoskeletons (ASEs) can reduce shoulder muscle activity during overhead work, but their effects on muscle synergy structure and temporal activation remain limited. We examined the effects of using three different exoskeletons on muscle synergies during simulated overhead tasks. Muscle activity from 18 participants (gender-balanced) performing both pseudo-static and dynamic tasks across 24 conditions (three ASEs and a control condition) was analyzed using non-negative matrix factorization to extract synergy number, structure, and activation coefficients. Dynamic tasks recruited more muscle synergies (interquartile range: 2–5) than pseudo-static tasks (interquartile range: 1–3), with some task combinations showing modest increases with ASE use compared to the control condition. Synergy structure and temporal activation were generally similar across interventions (mean cosine similarity 0.74–0.92), but certain ASE-task combinations produced significant local changes in synergy structure. Using exoskeletons generally altered muscle weightings, shifting from primary arm-elevating and shoulder-stabilizing muscles toward modules involving neck and back muscles, suggesting compensatory strategies for device-imposed biomechanical demands. Activation time courses remained highly similar across most interventions during pseudo-static tasks, though dynamic tasks showed reduced peak magnitude with exoskeleton use. Our results indicate that while modular motor control is largely preserved with ASE use, device- and task-specific adaptations in synergy structure and temporal activation can occur. Future research should explore how ASE design features influence neuromuscular strategies and assess long-term adaptation of muscle synergies in occupational settings.
{"title":"Muscle synergy analysis of short-term adaptation to arm-support exoskeletons during pseudo-static and dynamic overhead tasks","authors":"Hanjun Park , Maury A. Nussbaum","doi":"10.1016/j.jbiomech.2025.113135","DOIUrl":"10.1016/j.jbiomech.2025.113135","url":null,"abstract":"<div><div>Occupational arm-support exoskeletons (ASEs) can reduce shoulder muscle activity during overhead work, but their effects on muscle synergy structure and temporal activation remain limited. We examined the effects of using three different exoskeletons on muscle synergies during simulated overhead tasks. Muscle activity from 18 participants (gender-balanced) performing both pseudo-static and dynamic tasks across 24 conditions (three ASEs and a control condition) was analyzed using non-negative matrix factorization to extract synergy number, structure, and activation coefficients. Dynamic tasks recruited more muscle synergies (interquartile range: 2–5) than pseudo-static tasks (interquartile range: 1–3), with some task combinations showing modest increases with ASE use compared to the control condition. Synergy structure and temporal activation were generally similar across interventions (mean cosine similarity 0.74–0.92), but certain ASE-task combinations produced significant local changes in synergy structure. Using exoskeletons generally altered muscle weightings, shifting from primary arm-elevating and shoulder-stabilizing muscles toward modules involving neck and back muscles, suggesting compensatory strategies for device-imposed biomechanical demands. Activation time courses remained highly similar across most interventions during pseudo-static tasks, though dynamic tasks showed reduced peak magnitude with exoskeleton use. Our results indicate that while modular motor control is largely preserved with ASE use, device- and task-specific adaptations in synergy structure and temporal activation can occur. Future research should explore how ASE design features influence neuromuscular strategies and assess long-term adaptation of muscle synergies in occupational settings.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"195 ","pages":"Article 113135"},"PeriodicalIF":2.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145810048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-22DOI: 10.1016/j.jbiomech.2025.113026
Jeffrey A. Turner , Adam W. Kiefer , Garrett S. Bullock , Kristen L. Kucera , Kenneth L. Cameron , Michelle C. Boling , Stephen W. Marshall , Darin A. Padua
Markerless motion capture systems offer promising alternatives to traditional marker-based systems for biomechanical assessment, but their measurement properties require thorough validation before widespread adoption. This study assessed the reliability of trunk and lower extremity joint angles and predictive validity of OpenCap, a markerless motion capture system, during a jump-landing task. Thirty-three healthy individuals performed a total of 15 jump-landing trials under two sessions: 5 self-selected (natural) landings during the first session and another 5 natural and 5 verbally cued stiff landings during the second session. Trunk and lower extremity joint angles were captured from two simultaneously operated OpenCap systems. Intersystem and test–retest reliability was assessed by computing intraclass correlation coefficients (ICC) and minimal detectable changes (MDC). Predictive validity was evaluated using area under the receiver operator characteristic (AUC) from a mixed effect logistic regression model to determine whether OpenCap-derived joint angles could accurately identify verbally cued landing conditions (natural and cued stiff). OpenCap demonstrated moderate to excellent intersystem reliability (Range: ICC2,1: 0.79–1.00) and test–retest reliability (Ranges: ICC2,k: 0.70–0.97; MDC: 1.89–11.62˚) across all joint angles. Additionally, OpenCap successfully distinguished between natural and cued stiff landings (AUC = 0.92; 95% CI: 0.90, 0.94]). By offering an accessible and efficient alternative to traditional marker-based motion capture systems, OpenCap has the potential to enhance movement assessment, injury screening, and rehabilitation monitoring in both clinical and field settings.
{"title":"Reliability and predictive validity of trunk and lower extremity kinematics during a jump-landing task using OpenCap markerless motion capture system","authors":"Jeffrey A. Turner , Adam W. Kiefer , Garrett S. Bullock , Kristen L. Kucera , Kenneth L. Cameron , Michelle C. Boling , Stephen W. Marshall , Darin A. Padua","doi":"10.1016/j.jbiomech.2025.113026","DOIUrl":"10.1016/j.jbiomech.2025.113026","url":null,"abstract":"<div><div>Markerless motion capture systems offer promising alternatives to traditional marker-based systems for biomechanical assessment, but their measurement properties require thorough validation before widespread adoption. This study assessed the reliability of trunk and lower extremity joint angles and predictive validity of OpenCap, a markerless motion capture system, during a jump-landing task. Thirty-three healthy individuals performed a total of 15 jump-landing trials under two sessions: 5 self-selected (natural) landings during the first session and another 5 natural and 5 verbally cued stiff landings during the second session. Trunk and lower extremity joint angles were captured from two simultaneously operated OpenCap systems. Intersystem and test–retest reliability was assessed by computing intraclass correlation coefficients (ICC) and minimal detectable changes (MDC). Predictive validity was evaluated using area under the receiver operator characteristic (AUC) from a mixed effect logistic regression model to determine whether OpenCap-derived joint angles could accurately identify verbally cued landing conditions (natural and cued stiff). OpenCap demonstrated moderate to excellent intersystem reliability (Range: ICC<sub>2,1</sub>: 0.79–1.00) and test–retest reliability (Ranges: ICC<sub>2,</sub><em><sub>k</sub></em>: 0.70–0.97; MDC: 1.89–11.62˚) across all joint angles. Additionally, OpenCap successfully distinguished between natural and cued stiff landings (AUC = 0.92; 95% CI: 0.90, 0.94]). By offering an accessible and efficient alternative to traditional marker-based motion capture systems, OpenCap has the potential to enhance movement assessment, injury screening, and rehabilitation monitoring in both clinical and field settings.</div></div>","PeriodicalId":15168,"journal":{"name":"Journal of biomechanics","volume":"194 ","pages":"Article 113026"},"PeriodicalIF":2.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145360978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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