Journal Of Applied Biomechanics[JOURNAL]
Sun
200 papers
Erratum. Validity of Poststroke Gait Spatiotemporal and Joint Excursion Metrics Between Inertial Measurement Units and a Marker-Based System.
Journal of Applied Biomechanics
J Appl Biomech · 2026 Jun · PMID 42349844 · Publisher ↗
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The Influence of Different Starting Block Distances on Internal Tibial Load in Elite Sprinters.
Lu Z, Shao E, Sun D … +5 more , Wen J, Goda TJ, Song Y, Zhu J, Gu Y
J Appl Biomech · 2026 Jun · PMID 42269706 · Publisher ↗
In sprint running, the starting block distance (SBD) directly influences an athlete's start performance, yet there is a lack of research exploring how block distance affects internal tibial load. Therefore, this study ex...
In sprint running, the starting block distance (SBD) directly influences an athlete's start performance, yet there is a lack of research exploring how block distance affects internal tibial load. Therefore, this study examined internal tibial loading in 28 elite sprinters using finite element analysis. Maximum principal stress, shear stress, total deformation, and bending moments were assessed under 3 front block distances (50%, 60%, and 70% of leg length). A 2-way analysis of variance evaluated the effects of gender, SBD, and their interaction. The results showed a significant main effect of gender on maximum principal stress (P < .001), tibial bending moment (P < .001), maximum shear stress (P < .001), and total deformation (P < .001). Furthermore, significant gender-by-SBD interactions for maximum principal stress (P = .001, ηp2=.16) and maximum shear stress (P = .02, ηp2=.05) indicated distinct mechanical responses between male and female athletes in response to SBD settings. This finding suggests that adopting block settings previously reported to optimize start performance (eg, front block distance [FB]/interblock spacing length [SL] 50/45) may inevitably increase internal tibial loading, potentially elevating the risk of cumulative injuries such as medial tibial stress syndrome.
Altered Lower-Limb Dynamics in Stop-Jump Activity of Adolescents With Major Thoracic Scoliosis.
Dizaji E, Farahpour N, Ghazaleh L
J Appl Biomech · 2026 Jun · PMID 42248434 · Publisher ↗
Adolescent idiopathic scoliosis (AIS) may alter lower-limb biomechanics and neuromuscular control in high-demanding activities, like stop-jump. Understanding these alterations is crucial for effective rehabilitation. Thi...
Adolescent idiopathic scoliosis (AIS) may alter lower-limb biomechanics and neuromuscular control in high-demanding activities, like stop-jump. Understanding these alterations is crucial for effective rehabilitation. This study aimed to compare lower-limb biomechanics during stop-jump between AIS and healthy individuals. Twelve physically active adolescents with major thoracic AIS and 12 matched controls were recruited. A motion analysis system and 2 force plates recorded kinematic data and ground reaction forces, based on which the angles, velocities, moments, and power of the lower-limb joints were calculated and compared between the 2 groups. Results indicated that the AIS group exhibited greater hip power (P = .04) and extension velocity (P = .03) in takeoff and reduced hip abduction angle (P = .005) and velocity (P = .004) with increased hip abduction moment (P = .01) in landing. They also demonstrated altered knee rotation (P = .02) and a shorter time to stability (P < .05) after landing. The spinal deformity in AIS leads to altered hip and knee biomechanics during stop-jump tasks. The scoliosis group exhibited increased hip power and altered joint kinematics during takeoff, alongside a stiffer landing pattern. These changes highlight a disrupted kinetic chain, underscoring the need for rehabilitation that addresses both spinal and lower-limb mechanics.
Biomechanical Differences During Overground Walking in Virtual Reality: A Comparative Study With a Real Environment.
Tao Z, Luecha T, Loh PY … +2 more , Saito S, Muraki S
J Appl Biomech · 2026 Jun · PMID 42242381 · Publisher ↗
Realistically simulating natural walking is essential to create an immersive virtual reality experience. However, differences between the virtual reality environment (VRE) and real environment (RE) can alter gait charact...
Realistically simulating natural walking is essential to create an immersive virtual reality experience. However, differences between the virtual reality environment (VRE) and real environment (RE) can alter gait characteristics. Therefore, this study aimed to investigate differences in lower limb spatiotemporal parameters, joint kinematics, and muscle activity between overground walking in a VRE and RE. A total of 13 participants walked at 3 cadences (60 steps per minute [SPM], 80 SPM, and 100 SPM) in the VRE and RE. Motion capture and electromyography were employed to collect the spatiotemporal gait parameters, muscle activities of the right tibialis anterior and medial gastrocnemius muscles, and right lower limb joint angles of the participants. Our results showed that overground walking in the VRE altered several spatiotemporal gait parameters. In addition, the mean electromyography activity of the tibialis anterior and medial gastrocnemius muscles was reduced in the VRE during the initial double- and single-support phases. Most measured biomechanical parameters showed no significant interaction between the walking cadence and environment. This study clarifies biomechanical differences underlying the more cautious gait observed in a VRE, offering practical implications to enhance usability and optimize virtual reality locomotion design.
The Influence of Relative Schoolbag Mass on Gait Biomechanics of South African Adolescents: The Role of Sex and Grade.
Gambelli CN, Peens S, van Oort AF … +1 more , Kramer M
J Appl Biomech · 2026 May · PMID 42208605 · Publisher ↗
Heavy schoolbags are common among school-aged adolescents, yet biomechanical consequences across developmental stages and between sexes remain poorly defined, especially in low- and middle-income countries. This study in...
Heavy schoolbags are common among school-aged adolescents, yet biomechanical consequences across developmental stages and between sexes remain poorly defined, especially in low- and middle-income countries. This study investigated the effect of schoolbag carriage on gait in South African adolescents. A total of 186 injury-free adolescents (ages 12-18) completed barefoot walking trials over a pressure platform under unloaded and loaded conditions. Spatiotemporal and kinetic gait parameters were recorded and normalized to body height and weight. Analyses included (1) comparison of schoolbag mass by sex and grade (ie, school year); (2) evaluation of gait by loading condition, grade, and sex; and (3) prediction of loaded-condition gait parameters by relative schoolbag mass. Grades 8 to 11 carried higher absolute loads and grade 8 carried highest relative loads, with 58% exceeding 15% body mass, but no sex differences were found. Load carriage increased stance and double support time; reduced swing phase; and elevated vertical forces, pressures, and loading rates. Females exhibited higher forefoot and midfoot pressures and narrower step width. Relative schoolbag mass predicted greater forefoot/heel loads, lower midfoot loads, and narrower step width. Schoolbag carriage imposes substantial biomechanical demands, particularly in early adolescence and among females, emphasizing need for age- and sex-specific guidelines to mitigate long-term musculoskeletal risk.
Influence of Body Configuration on Kinetics and Multijoint Control Strategies Sprinters Use During the First Step Out of Blocks.
Stewart HE, Wilcox RR, McNitt-Gray JL
J Appl Biomech · 2026 May · PMID 42150746 · Publisher ↗
Sprinters need to generate horizontal impulse quickly in the first step out of the blocks to accelerate the body toward the finish line. The purpose of this study was to determine how body configuration at initial foot c...
Sprinters need to generate horizontal impulse quickly in the first step out of the blocks to accelerate the body toward the finish line. The purpose of this study was to determine how body configuration at initial foot contact was correlated to ground reaction force measures and multijoint control during the first step out of the blocks by highly trained to world-class sprinters. Measurements of ground reaction forces and segment kinematics during sprint starts performed during a training session revealed that positioning the foot further behind the center of mass at initial contact significantly correlated with shorter contact times, greater average horizontal forces, and increased net joint moment impulse on the knee during the impact phase. Increases in average horizontal forces were significantly correlated with smaller magnitudes of shank angular velocity during the impact phase and shorter times to peak thigh angular velocity during the postimpact phase. We also used kinetic and kinematic data to provide feedback regarding an athlete's mechanics to coaches for use within a training session on the track.
Assessing the Validity of Whole-Body and Segmental Angular Momenta During Walking in Older Individuals With and Without Transtibial Limb Loss.
Monteiro AS, Fey NP, Major MJ
J Appl Biomech · 2026 May · PMID 42114827 · Full text
Older individuals (≥65 y old) with and without lower limb loss experience a high prevalence of falls. Minimizing fall risk depends on an individual's ability to maintain dynamic balance. A metric often used to characteri...
Older individuals (≥65 y old) with and without lower limb loss experience a high prevalence of falls. Minimizing fall risk depends on an individual's ability to maintain dynamic balance. A metric often used to characterize an individual's ability to regulate dynamic balance is angular momenta during steady-state walking. However, a gap exists in the validity of angular momenta as a measure of dynamic balance in these cohorts. The goal of this study was to evaluate the validity of angular momenta in older individuals with and without transtibial amputation during walking through assessments of construct and criterion validity. Construct and criterion validity were evaluated through correlations of momenta with clinical balance measures and prospective fall numbers over 12 months, respectively. For context, falls were categorized by pattern and scenario. Angular momenta of walking demonstrated evidence of construct and criterion validity in both groups through moderate-to-strong correlations with clinical balance measures and prospective falls. These relationships also varied between groups. The most common pattern and scenario of falls in both groups were trips and level-ground walking, respectively. This study contributes evidence that angular momentum during level-ground walking is a valid measure of dynamic balance in older persons with and without transtibial amputation.
Agreement and Repeatability of a Smartphone-Based Markerless System (OpenCap) Versus Marker-Based Motion Capture During Treadmill Walking and Running.
Borba EF, Inda AR, Herberts BM … +8 more , Alves LL, Ibrahim BM, Fernandes FMM, Palma NR, Hoffmann GO, da Silva RM, Peyré-Tartaruga LA, Tartaruga MP
J Appl Biomech · 2026 May · PMID 42097592 · Publisher ↗
Marker-based motion capture is the gold standard for 3-dimensional gait analysis but is expensive and largely confined to specialized laboratories. Smartphone-based markerless tools such as OpenCap could scale gait asses...
Marker-based motion capture is the gold standard for 3-dimensional gait analysis but is expensive and largely confined to specialized laboratories. Smartphone-based markerless tools such as OpenCap could scale gait assessment, yet their validity and repeatability during treadmill walking and running remain unclear. We evaluated agreement and within-session repeatability between OpenCap and motion capture during treadmill walking (4 km·h-1) and running (8 and 14 km·h-1) in 10 healthy adults, recorded simultaneously with both systems. We computed spatiotemporal variables, sagittal hip/knee/ankle angle waveforms and range of motion, and center-of-mass displacement waveforms and range of motion. Agreement was assessed with Bland-Altman, intraclass correlation coefficients, Pearson r, and root mean square error; repeatability with trial-to-trial SD, coefficient of variation, and waveform variability index (GaitSD). Spatiotemporal metrics showed bias close to 0 and very strong associations (r ≥ .96), with small minimum detectable changes (eg, ≤0.01 m for stride length and ≤0.03 s for temporal variables). Sagittal range of motion showed good-to-excellent reliability (bias: ≈-4.5° to 2.9°, intraclass correlation coefficients = .76-.93). Waveform root mean square error was ≈1° to 4° for joint angles and ≈0.1 to 0.5 cm for center of mass, and statistical parametric mapping indicated only localized differences. Repeatability and GaitSD were comparable between systems across variables and speeds. Under controlled treadmill conditions, OpenCap showed comparable performance and repeatability metrics to motion capture.
Reliability and Validity of a Low-Cost and Portable Dynamometer: Toward a Simple Clinical Test for Assessing Plantar Flexor Strength.
Leclercq A, Pommerell F, Cattagni T … +2 more , Morel B, Rahmani A
J Appl Biomech · 2026 May · PMID 42086218 · Publisher ↗
Plantar flexor weakness is common in orthopedic and neurological disorders and requires reliable strength assessment tools. This study evaluates the validity and reliability of a portable strain gauge dynamometer compare...
Plantar flexor weakness is common in orthopedic and neurological disorders and requires reliable strength assessment tools. This study evaluates the validity and reliability of a portable strain gauge dynamometer compared with a gold-standard instrumented dynamometer. Thirty-five healthy adults were divided into 2 groups: one for validation against the reference device and another for test-retest reliability assessment. Pearson correlations, Bland-Altman analyses, and intraclass correlation coefficients were performed on plantar flexor maximal force and torque data. A strong correlation (r = .84, 95% CI: .59-.94, P < .001) confirmed the portable strain gauge dynamometer's validity, with a slight torque underestimation (-4.6% [20.5%]). Bland-Altman analysis indicated a mean bias of -4.34 N·m with 95% limits of agreement ranging from -27.9 to 19.2 N·m. Reliability was excellent across sessions and raters (intraclass correlation coefficients = .889-.926; standard error of measurement = 43.2-55.6 N·m). Absolute reliability analyses suggested that only changes above ∼120 to 155 N exceeded measurement error. These results support that the strain gauge dynamometer, fixed to a stable surface, is a valid and reliable tool for assessing plantar flexor strength in clinical settings.
Ear-Worn Inertial Sensors Can Predict Gait Metrics and Reconstruct Vertical Ground Reaction Force Curves During Running.
Stuchbury-Wass J, Ciliberto M, Butkow KJ … +5 more , Yang Q, Liu Y, Preatoni E, Ma D, Mascolo C
J Appl Biomech · 2026 Apr · PMID 42034346 · Publisher ↗
Ear-worn wearables (aka: earbuds, hearables, or earables) are commonly used by runners for entertainment, and many modern devices also include inertial sensors for user interaction. We propose harnessing the technology e...
Ear-worn wearables (aka: earbuds, hearables, or earables) are commonly used by runners for entertainment, and many modern devices also include inertial sensors for user interaction. We propose harnessing the technology embedded in earbuds to capture fundamental aspects of running mechanics and make them available to the wider community of users, outside a lab setting. While other wearables such as insoles or ankle-/sacrum-mounted inertial measurement units have already been presented, ear-worn devices may have a better potential for adoption and therefore offer an optimal compromise between validity of running gait analysis and usability. Thirty healthy participants (18 males, 12 females) ran on an instrumented treadmill (54,000 gait cycles) and floor-mounted force plates (2800 gait cycles) at a variety of speeds. Building on the information brought about by the vibrations transmitted to, and motion of, the head, we devised a gait event detection algorithm and a regression model to predict vertical ground reaction force waveforms. The validation of outcomes against quantities from force plates shows an average mean absolute percentage error of 4.8% on temporal metrics and 9.0% on scalar ground reaction force derived metrics. Additionally, the model tracks the full vertical ground reaction force curve well, achieving an normalized root mean square error of 11.1% on unseen participants. Overall, we show comparable accuracy from an ear-worn consumer device in temporal and kinetic gait parameter estimation to specialist devices, paving the way for accessible running gait monitoring.
The Jump Throw Proximal-to-Distal Sequence-Contribution of the Proximal Segments to the Shoulder Kinematics.
Árnason K, Agustsson A, Briem K
J Appl Biomech · 2026 Apr · PMID 42034343 · Publisher ↗
Kinematic descriptions of the handball jump throw are scarce, and the influence of proximal kinematics on peak shoulder internal rotation (IR) angular velocity during a jump throw is not well understood. Positional kinem...
Kinematic descriptions of the handball jump throw are scarce, and the influence of proximal kinematics on peak shoulder internal rotation (IR) angular velocity during a jump throw is not well understood. Positional kinematic differences related to on-field demands also remain underexplored. This cross-sectional study analyzed jump throws (n = 41; central/back players = 20, wing/pivot players = 21) using 3D motion capture. The proximal-to-distal sequence was evaluated by comparing the timing of peak angular velocities across joints and segments (paired t tests). Peak angular velocity and joint range of motion excursion were compared between central/back and wing/pivot players (independent t test). Correlation coefficients assessed associations between proximal and distal variables, and significant variables were entered into a hierarchical regression to determine their contribution to shoulder IR angular velocity. Results revealed a proximal-to-distal sequence pattern. Central/back players demonstrated higher peak angular velocities in most segments, along with increased range of motion in the hip, pelvis, and thorax. Hip and pelvis kinematics explained 44% of the variance in peak shoulder IR angular velocity (R2 = .44, P = .001). This is the first study to highlight the substantial influence of proximal kinematics on shoulder IR angular velocity in the jump throw. Observed positional differences underscore the need for position-specific strength and power training strategies in handball.
Trunk Postural Control During Unstable Sitting Does Not Explain Whole-Body Angular Momentum Control During Walking Among Individuals With Unilateral Lower Limb Amputation.
Golyski PR, Hendershot BD, Butowicz CM
J Appl Biomech · 2026 Apr · PMID 42034341 · Publisher ↗
During walking, uninjured individuals maintain whole-body angular momentum (WBAM) within a narrow range. Individuals with lower limb amputation (LLA) have demonstrated larger WBAM ranges during walking relative to uninju...
During walking, uninjured individuals maintain whole-body angular momentum (WBAM) within a narrow range. Individuals with lower limb amputation (LLA) have demonstrated larger WBAM ranges during walking relative to uninjured controls, suggesting disrupted WBAM control. Given that the trunk is a principal contributor to WBAM and trunk control may be altered after LLA, we related trunk postural control isolated during unstable sitting and WBAM control during walking across 9 individuals with unilateral transfemoral amputation, 24 individuals with unilateral transtibial amputation, and 16 uninjured controls. Linear regressions revealed weak relationships (R2 = .050-.350, P < .071), particularly in the sagittal and transverse planes, between trunk postural control measures and WBAM ranges. Trunk postural control measures during unstable sitting were larger among individuals with LLA versus uninjured controls (P < .029) but were not different between individuals with transtibial amputation versus transfemoral amputation. Similarly, WBAM ranges during walking were larger in all planes between individuals with LLA versus uninjured controls (P < .005), with individuals with transtibial amputation having larger ranges than individuals with transfemoral amputation in the sagittal (P < .001) and frontal (P = .006) but not the transverse (P = 1.000) planes. Our findings suggest that trunk postural control during unstable sitting does not explain differences in WBAM control during walking among individuals with versus without LLA, particularly in the sagittal and transverse planes.
Manual Load Carriage Impairs Compensatory Step Reactions to Recover Balance.
Marchant HJ, Zettel JL
J Appl Biomech · 2026 Apr · PMID 41997576 · Publisher ↗
Manual materials handling is a common occupational task associated with workplace falls. The aim of this study was to examine whether an anterior manual load impacts balance recovery via compensatory stepping. Step recov...
Manual materials handling is a common occupational task associated with workplace falls. The aim of this study was to examine whether an anterior manual load impacts balance recovery via compensatory stepping. Step recovery following unpredictable perturbations to standing were compared with and without a manual load in 12 young healthy male and female adults. Recovery from forward perturbations was measured via the margin of stability during and following the step, as well as by step coordination in terms of maintaining lateral stability in shifting support between legs when stepping, along with step timing and placement. While the load did not affect forward destabilization during the step, it did delay the reversal of the falling motion after landing the foot. Moreover, the load disrupted lateral stability control such that a greater fall toward the unsupported step-leg side occurred but with no increase in step-width to compensate. Step-length was also unchanged, but the load did elicit slightly earlier step timing that in turn reduced the prestep interval to enact lateral weight shifts. These results show that a load compromises step recovery by delaying poststep restabilization and disrupting step coordination, identifying step response efficacy as a possible factor in fall risk associated with manual loads.
Behind the Curtain of the Faculty Job Interview Process.
Johnson RT, Sánchez N
J Appl Biomech · 2026 Apr · PMID 41997573 · Publisher ↗
Securing a faculty position is the final milestone for many individuals completing their PhD or postdoctoral training. However, navigating the academic job market can feel like a full-time endeavor, which often has to be...
Securing a faculty position is the final milestone for many individuals completing their PhD or postdoctoral training. However, navigating the academic job market can feel like a full-time endeavor, which often has to be balanced alongside tasks like manuscript preparation, dissertation completion, or grant applications. Despite extensive training in research and teaching, many candidates report feeling underprepared for the multifaceted and often hidden nature of the faculty interview process. Furthermore, seeking guidance about this process can be intimidating for some, as individuals may lack access to a career development mentoring team. As part of the 2024 American Society of Biomechanics Annual Meeting's Career Development roundtables, the authors, drawing from their experiences as both applicants and interviewers, compiled key considerations to support aspiring faculty members. This resource aims to: (1) offer a structured approach to initiating the faculty application process and (2) highlight departmental expectations during interviews to help candidates prepare effectively and present themselves confidently. By sharing practical strategies and insights, we hope to empower future faculty to successfully identify, apply for, interview for, negotiate, and accept academic positions.
The Influence of Standing-Induced Low Back Pain on Spatiotemporal Gait Variables and Trunk-Pelvis Kinematics.
Gallagher KM, Schmitt AC, Nelson-Wong E … +3 more , Throckmorton S, Aston K, Austin G
J Appl Biomech · 2026 Apr · PMID 41991146 · Publisher ↗
Standing-induced low back pain (LBP), wherein individuals with no LBP history report pain during prolonged standing, can be prevented by altered lumbopelvic posture and/or increased movement. Walking breaks can reduce st...
Standing-induced low back pain (LBP), wherein individuals with no LBP history report pain during prolonged standing, can be prevented by altered lumbopelvic posture and/or increased movement. Walking breaks can reduce standing-induced LBP. Although LBP and walking are typically studied in the context of chronic pain, the standing-induced pain model can establish whether altered gait mechanics precede pain and whether movement after standing reduces pain. This study used a standing-induced LBP paradigm to assess effects of standing on spatiotemporal gait parameters and trunk-pelvis kinematics. Participants stood for 75 minutes completing computer tasks, with prestanding and poststanding walking recorded using markerless motion capture. Ten of 31 participants developed LBP during standing; however, their gait changes differed from those in the literature for chronic LBP. Pain-developing participants showed less trunk-pelvis lateral bend deviation angle during walking. Trunk axial twist deviation phase angle increased, which may signal a redistribution of force across different tissues following a pain-inducing task or reduced function of the deep stabilizer muscles of the spine, resulting in more movement variability. Future work will measure muscle activity throughout walking and standing to link kinematics and muscle activity and explore whether walking at different speeds may alter pain development.
The Contribution of Muscle-Tendon Interactions to Superior Running Economy: An Uphill Versus Level Running Paradigm.
Swinnen W, Hoogkamer W, Segers V
J Appl Biomech · 2026 Apr · PMID 41946452 · Publisher ↗
Trained runners exhibit better running economy (RE) during level running than untrained individuals, though the underlying contributors remain unclear. Using an indirect approach, we explored whether more effective muscl...
Trained runners exhibit better running economy (RE) during level running than untrained individuals, though the underlying contributors remain unclear. Using an indirect approach, we explored whether more effective muscle-tendon interactions might explain this superior RE. We measured RE, biomechanics, and lower limb muscle activation in 16 runners and 16 aerobically fit nonrunners during level (1.7 and 3.5 m/s) and uphill (+8.1°, 1.7 m/s) running. Unlike level running, uphill running requires net positive mechanical work, reducing the contribution of fine-tuned muscle-tendon interactions to RE. Therefore, we hypothesized that RE differences between runners and nonrunners would be smaller during uphill running. Our results confirmed that runners had better RE on level ground (P ≤ .046) but showed no RE advantage during uphill running (P = 1.00). Across all conditions, runners ran with higher average positive and negative ankle joint power (P ≤ .010) and a greater relative contribution of the ankle to the total positive joint power (P = .037). Despite this increased ankle reliance, relative triceps surae muscle activation was similar between groups. These findings suggest that superior RE observed in runners on level ground may stem from more optimized interaction between the triceps surae muscles and the Achilles tendon.
Comparison of Circular and Ellipse-Based Methods for Assessing Coordination Variability.
Jeong H, van Emmerik R
J Appl Biomech · 2026 Apr · PMID 41934959 · Publisher ↗
Vector coding is a widely adopted technique for analyzing coordination variability, but traditional circular statistics methods with finite difference are sensitive to outliers and artifacts, potentially affecting the ac...
Vector coding is a widely adopted technique for analyzing coordination variability, but traditional circular statistics methods with finite difference are sensitive to outliers and artifacts, potentially affecting the accuracy of assessments. To address the limitation, Ellipse-based methods using finite difference or angular velocity have been proposed, but formal statistical comparisons have not been performed. Therefore, this study aimed to (1) assess coordination variability using 3 distinct vector coding methods: circular statistics with finite difference, ellipse-based coding with finite difference, and ellipse-based coding with angular velocity; and (2) examine how each method responds to changes in coordination variability resulting from variations in gait speed. Comparing coordination variability across these methods, the circular statistics method differed from the ellipse methods (ELMs) throughout the gait cycle, while the 2 ELMs showed similar patterns but responded differently to gait speed changes due to input variable differences. Notably, only the ELM with angular velocity consistently detected gait speed-related increases in coordination variability, suggesting caution when comparing findings across studies due to their methodological incompatibility. Furthermore, our findings indicate that the ELM incorporating angular velocity may be the most sensitive for detecting changes in gait speed.
Lower Limb Muscle Activation and Ground Reaction Forces During Forward Drop Lunges From Varying Heights.
Günay A, Gülmez İ
J Appl Biomech · 2026 Apr · PMID 41927029 · Publisher ↗
This study investigated lower limb muscle activation and vertical ground reaction forces (GRF) during forward drop lunges from 3 different heights (0, 10, and 20 cm). Twenty-three active male athletes (mean age 21 [2] y;...
This study investigated lower limb muscle activation and vertical ground reaction forces (GRF) during forward drop lunges from 3 different heights (0, 10, and 20 cm). Twenty-three active male athletes (mean age 21 [2] y; height 178 [6] cm; body mass 70 [9] kg; body mass index 21 [4]) participated. Surface electromyography was recorded from the biceps femoris, vastus lateralis, rectus femoris, and vastus medialis muscles. After maximum voluntary contraction assessment, participants performed drop lunges onto a force platform. Electromyography signals were filtered and normalized to maximum voluntary contraction using MATLAB. Repeated-measures analysis of variance and paired t-tests evaluated the effects of height and side. During the eccentric phase, significant differences emerged in biceps femoris and rectus femoris activation depending on height (P < .05). In the concentric phase, all muscles except left vastus medialis showed significant differences (P < .05). Concentric activation and left-side muscle activity were significantly higher than eccentric and right-side activity, respectively. GRF values increased significantly with drop height (P < .05). However, only concentric phase muscle activation showed a linear relationship with height. These findings suggest that manipulating platform height in lunge training can effectively increase quadriceps activation and GRF without external load, especially in the concentric phase, and may enhance lower-limb strength and performance.
Minimum Slip Perturbation Amplitudes Required to Identify Altered Kinematics and Muscle Excitations.
Beyer C, Feldman J, Allen J … +1 more , Franz JR
J Appl Biomech · 2026 Mar · PMID 41921954 · Publisher ↗
Monitoring instability is critical for diagnosing falls risk and preventing fall events. This study aimed to establish minimum slip perturbation amplitudes required for identification of altered signals via surface elect...
Monitoring instability is critical for diagnosing falls risk and preventing fall events. This study aimed to establish minimum slip perturbation amplitudes required for identification of altered signals via surface electromyography and inertial measurement units in the context of conscious perception thresholds. We tested the null hypothesis that minimum detectable amplitudes for conscious perception would be indistinguishable from those for electromyography and inertial measurement unit signals. Fifteen healthy younger adults participated. After each perturbation, participants were asked if they had perceived the perturbation. The average conscious perception threshold was 0.061 m/s (ie, Δ velocity). Minimal detectable effects were based on the fraction of signals exceeding 3 standard deviations of unperturbed walking. For electromyography, we found thresholds of 0.053 m/s for the tibialis anterior and 0.018 m/s for the gastrocnemius. For IMUs, we found thresholds for most anatomical placements of ≤0.016 m/s. Clear differences in minimal detectable amplitudes for local muscle reflexes versus conscious perception support exploring this experimental paradigm for screening in individuals with sensory, motor, and cognitive-motor pathologies. We also conclude that inertial measurement unit signals are highly sensitive to slip perturbations in walking, supporting continued development into their application for monitoring and measuring instability in the real world.
Lower-Extremity Interjoint Coordination During Stair Ascent in Knee Osteoarthritis and the Therapeutic Response to Tai Chi Training.
Chai Y, Zheng J, Liu D … +4 more , Guo M, Ma Y, Wang X, Hou M
J Appl Biomech · 2026 Jun · PMID 41921951 · Publisher ↗
Knee osteoarthritis (OA) alters lower-extremity kinematics during stair ascent, but interjoint coordination changes remain unclear. Improving coordination and balance is also a critical target for knee OA rehabilitation....
Knee osteoarthritis (OA) alters lower-extremity kinematics during stair ascent, but interjoint coordination changes remain unclear. Improving coordination and balance is also a critical target for knee OA rehabilitation. This study compared lower-extremity interjoint coordination during stair ascent between 69 knee OA individuals and 30 age-matched healthy older adults. Knee OA participants were randomized into Tai Chi or control (balance and postural training) groups, receiving 12-week interventions. 3D motion analysis assessed interjoint coordination via perimeter, area, and coordination coefficient of cyclogram at baseline and postintervention. Compared with healthy elderly, individuals with knee OA exhibited greater sagittal plane joint excursions, increased hip-knee angular range, and less smooth cyclograms. Postintervention, both groups exhibited reduced excursions in the sagittal and frontal planes, with greater reductions observed in the control group. The Tai Chi group showed decreased hip-ankle and knee-ankle angular ranges, whereas the control group displayed reduced hip-knee ranges, both shifting coordination parameters toward healthy levels. Only the sagittal plane hip-knee cyclogram area differed significantly between interventions, being smaller in the balance group. Knee OA impairs stair ascent coordination in elderly. Both interventions enhance coordination, but Tai Chi's benefits are predominantly sagittal specific, whereas balance training improves both planes and demonstrates superior efficacy in improving hip-knee flexion-extension coordination.
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