The control of mediolateral standing balance is disrupted in many clinical populations, likely due in part to altered sensation. Contributions of specific feedback sources to balance control can be investigated using sensory perturbations, as can be evoked with musculotendon vibration. The purpose of this study was to determine whether hip abductor vibration can elicit mediolateral sway at frequencies below 1 Hz, which dominate standing posture. Participants (n = 12) without neurological or orthopedic conditions performed a series of randomized standing trials on a force plate in which either hip abductor vibration was delivered or the standing surface translated mediolaterally. Vibration was delivered bilaterally in an out-of-phase pattern, with time-varying intensity following sum-of-sine trajectories with frequency content from 0.1 to 0.9 Hz. Surface translations followed similar sinusoidal trajectories, with the goal of increasing the likelihood that trials with vibration would be interpreted as reflecting true mediolateral sway. Participants were not instructed how to respond to the stimuli, and center of pressure location was calculated using recorded ground reaction forces and moments from the force plate. Vibration caused significant increases in mediolateral sway only at the specific frequencies targeted by each trajectory, suggesting that appropriately delivered hip vibration could shape mediolateral sway patterns through sensory augmentation.
Increased contralateral pelvic drop (CPD) during running is associated with running injuries, yet its direct influence on tissue loading remains unclear. The purpose of this study was to investigate how increased CPD affects internal loading at 4 common injury sites: the iliotibial band (ITB), Achilles tendon, patellofemoral joint (PFJ), and tibia. Eighteen healthy runners completed 2 overground running conditions at their 10 km pace: habitual running and increased CPD. Gait retraining with real-time visual feedback was used to alter pelvic drop. Kinetic and kinematic data were collected and musculoskeletal modeling estimated peak active and passive ITB strain, Achilles tendon force, PFJ contact force, and normal stress on the distal third of the tibia using elliptical beam theory. Participants increased peak CPD in the modified condition (-10.4° vs -6.0°, P < .001), resulting in increased passive and active tensor fascia latae component of the ITB strain (P < .05), with decreases in medial and lateral tibial stress (P < .05). No changes were observed in Achilles tendon force or PFJ contact force (P > .05). These results suggest increased CPD influences frontal plane mechanics and ITB loading but may not increase loading at other sites, including the Achilles tendon, PFJ, or distal tibia.
Carrying tasks are a part of everyday life for both able-bodied individuals and those with clinical gait asymmetries. While carrying tasks and gait asymmetries have each independently been associated with low back pain, the combination of these factors has received limited attention. We addressed this gap by employing an established experimental protocol to induce gait asymmetries with a clinical walking boot in healthy able-bodied participants (n = 12). Participants carried dumbbells weighing 7.5% and 15% of body weight in 1 or 2 hands. Low back joint and muscle forces estimated from a musculoskeletal model during asymmetric and symmetric gaits were compared. Our results indicated that normalized peak low back forces were mostly not impacted by gait asymmetry except when carrying the higher 15% load alone in the hand contralateral to the walking boot. Raw peak L5/S1 intervertebral joint compression (1291-3551 N) and shear (181-604 N) forces during all carrying tasks were below spinal unit tissue injury tolerances for manual materials handling. Future work should look to examine nonbiomechanical factors, alternative sources or levels of asymmetry, or other daily tasks that could contribute to low back pain in those with gait asymmetries.
Studying ground reaction force (GRF) is essential for in situ running analysis, as they provide critical insights into both performance optimization and the etiology of running-related injuries. However, the use of current measurement systems in ecological or field conditions remains limited: their restricted measurement areas constrain data collection to only a few steps, and their high cost hinders widespread adoption. Recently, a size-adjustable instrumented track has been developed to measure the vertical component of GRF outside the laboratory environment. Building on this advancement, the present study aims to develop a neural network approach for predicting the anteroposterior component from the measured vertical component and to evaluate the impact of prediction errors on joint kinetics. A public data set comprising 9500 running steps was used to train, validate, and test the prediction model. The results demonstrated that a convolutional neural network can accurately predict the anteroposterior component of the GRF (relative root mean square error = 7.44%). While these anteroposterior-GRF prediction errors had only a minor impact on ankle moment calculations, estimates at the knee and hip were more substantially affected. These findings suggest that the proposed model may be effectively applied in conjunction with the size-adjustable instrumented track.
This study aimed to identify key kinematic and kinetic factors that affect ball velocity in professional baseball pitchers, focusing on the role of pitching timing. It was hypothesized that pitchers in the high-velocity group (HG) would exhibit delayed timing of key pitching events, as well as greater pelvic and trunk kinematics, and higher ground reaction force (GRF) than those in the low-velocity group (LG). Based on ball velocity, this study categorized 40 professional pitchers registered with the Korea Baseball Organization into HG and LG. A Vicon motion capture system, force plates, and a speed gun were utilized to collect data on body segment motion, joint angular velocity, and GRF. Independent t-tests were conducted to compare differences between the 2 groups. The results revealed that the HG exhibited notably higher trunk angular velocity, drive leg anterior GRF impulse, and stride leg vertical GRF than the LG. Moreover, the HG demonstrated later stride foot contact, maximal external rotation, and ball release, indicating that delayed pitching timing contributes to increased ball velocity. These results highlight the importance of trunk rotation and GRF production for achieving high ball velocity. Furthermore, the timing of key pitching events is considered a distinguishing factor among elite pitchers.
Members of the Athletic Trainers' Osteoarthritis Consortium (ATOAC) participated in a harvest activity at the 2019 Annual Meeting as an initial step to identify common data elements that researchers should consider when studying osteoarthritis and posttraumatic osteoarthritis. The consortium decided on 6 primary categories (Physical Activity, Patient-Reported Outcomes, Biomechanics, Neural Function, Imaging, and Biomarkers) in which attending members were able to vote on which variables were considered most important when studying or treating patients with osteoarthritis and posttraumatic osteoarthritis. Workgroups were then comprised of experts within the ATOAC to explore these variables and the suitability for research implantation. The following information on Imaging and Biomarkers is presented to provide recommendations for researchers to adopt when developing patient-centered research for osteoarthritis and posttraumatic osteoarthritis to homogenize the literature for better patient outcomes.
Members of the Athletic Trainers' Osteoarthritis Consortium participated in a harvest activity at the 2019 Annual Meeting as an initial step to identify common data elements that researchers should consider when studying osteoarthritis and posttraumatic osteoarthritis. The consortium decided on 6 primary categories (Physical Activity, Patient-Reported Outcomes, Biomechanics, Neural Function, Imaging, and Biomarkers) in which attending members were able to vote on which variables were considered most important when studying or treating patients with osteoarthritis and posttraumatic osteoarthritis. Workgroups were then comprised of experts within the Athletic Trainers' Osteoarthritis Consortium to explore these variables and the suitability for research implantation. The following information on Biomechanics and Neural Function is presented to provide recommendations for researchers to adopt when developing patient-centered research for osteoarthritis and posttraumatic osteoarthritis to homogenize the literature for better patient outcomes.
Hamstring strains result in alterations to muscle function; however, evidence regarding how these changes affect balance performance remains limited. This study investigated the impact of altered hamstring function on balance control in athletes with hamstring injuries. Thirty-two participants (16 injured hamstrings and 16 controls) participated in this study. Hamstring properties and strength were assessed to evaluate muscle function. Participants performed maximum lean forward in both single- and double-leg stances under eyes-closed and eyes-open conditions on a force platform. Then, the center of pressure was analyzed. Injured athletes exhibited higher hamstring stiffness (P = .028) and decrement (P = .019), and lower strength (P = .024 at 0° and P = .005 at 90°). Also, they displayed a greater sway range in both the anteroposterior (P = .029) and mediolateral directions (P = .030), together with increased center of pressure velocity (P = .019) and a larger sway area (P = .020) during a forward lean task under eye-closed conditions. Significant associations were identified between hamstring function and balance control. These findings indicate that alterations in hamstring function following muscle strains contribute to impaired balance control. This factor should be considered in training and rehabilitation for athletes recovering from hamstring injuries.
Members of the Athletic Trainers' Osteoarthritis Consortium participated in a harvest activity at the 2019 Annual Meeting as an initial step to identify common data elements that researchers should consider when studying osteoarthritis and posttraumatic osteoarthritis. The consortium decided on 6 primary categories (Physical Activity, Patient-Reported Outcomes, Biomechanics, Neural Function, Imaging, and Biomarkers), and attending members were able to vote on which variables were considered most important when studying or treating patients with osteoarthritis and posttraumatic osteoarthritis. Workgroups were then comprised of experts within the Athletic Trainers'Osteoarthritis Consortium to explore these variables and the suitability for research implantation. The following information on Physical Activity and Patient-Reported Outcomes is presented to provide recommendations for researchers to adopt when developing patient-centered research for osteoarthritis and posttraumatic osteoarthritis to homogenize the literature for better patient outcomes.
In full marathons, a considerable slowdown that typically occurs after 30 km, often referred to as "hitting the wall," is well known, but the underlying biomechanical mechanism remains unclear. This study aimed to elucidate pacing patterns and kinematic changes in marathon runners. Hierarchical clustering of running pace per kilometer of 297 participants, obtained from 58 marathon races, identified 3 groups, each exhibiting different biomechanical changes tracked by wearable sensors. Two groups that experienced a slowdown showed decreases in step length (effect size [ES] = 0.40-1.43), step frequency (ES = 0.30-0.34), and vertical stiffness (ES = 0.55-0.65), along with an increase in contact time (ES = 0.56-0.86). The group that slowed down suddenly after 30 km displayed unchanged vertical oscillation, in contrast to the group that began slowing down earlier. The relationship among contact time, step length, and vertical stiffness observed differs from findings in laboratory tests with constant speed, suggesting that changes in step length in response to decreased vertical stiffness may contribute to the slowdown. The mechanism of sudden slowdown after 30 km, which is unique to marathon running, should be distinguished from slowdowns that occur earlier.
Scapular kinematics are influenced by age, but the relationship in older populations and across functional tasks needs further investigation. The objective of this study was to examine scapular and humeral kinematics during the Work-Related Activities and Functional Task protocol across a broad age range. Eighty healthy adults (46 [20] y; 170 [11] cm; 78.8 [16.8] kg) completed the Work-Related Activities and Functional Task protocol and 2 planar elevations while shoulder motion was tracked with optical motion capture. Scapular and humeral angles were assessed in relation to age. Pearson correlation analyses showed that scapular tilt was significantly ( P < .001) correlated with age at many humeral elevations during the comb hair ( r = .443–.490), wash axilla ( r = .478–.498), overhead reach ( r = .256–.406), and sagittal flexion ( r = .316–.426) movements. Two-way analyses of variance with sex and age group factors (older [>65] and younger [<35] only) revealed that the older group had significantly more scapular posterior tilt, and statistical parametric mapping independent t tests showed that older adults also used consistently more humeral elevation during several movements. These findings provide insight into the interacting influence of age and shoulder kinematics on shoulder musculoskeletal health.
Goaltending techniques have evolved to include goaltenders dropping to their knees to cover the lower part of the net, utilizing stances, such as the butterfly and reverse vertical horizontal (RVH). These stances are suggested to place considerable stress on the hip, knee, and ankle joints compared with traditional stances (eg, standing and vertical horizontal). However, the kinematic differences between these techniques and potential implications for injury risk have not been fully explored. This study aimed to quantify 3D lower-extremity joint kinematics during key goaltending stances. The 3D hip, knee, and ankle angles of 26 goaltenders (mean (SD): age = 19.5 (2.3) y) were quantified during key goaltending stances (ie, butterfly, standing ready, RVH, and vertical horizontal) using Theia3D markerless technology. The butterfly and RVH compared with the standing ready and vertical horizontal demonstrated higher mean hip internal rotation (16.6° and 22.2° vs 5.2° and 11.4°, respectively) and ankle external rotation (11.7° and 15.9° vs −1.6° and −10.8°). Compared with the standing ready, the kneeling stances (vertical horizontal, butterfly, and RVH) also involved higher mean knee abduction (5.6° vs 12.4° to 15.1°) and external rotation (0.7° vs 13.0° to 21.3°). The butterfly and RVH stances showed riskier kinematics for common hip, knee, and ankle injuries in goaltenders.
Market-available soccer footwear is predominantly designed according to male athlete mechanics. With known sex differences in cutting strategies, it should not be assumed that the female body can withstand the same amount of traction as males. Mechanical stability of the lower limbs is affected by fatigue, with negative effects most pronounced in female athletes. Soccer cleats could play a key role in moderating female athletes' exposure to torsional injury mechanisms across game play, such as those mechanisms in anterior cruciate ligament injury. This study investigates the influence of soccer cleat stud shape, elliptical, and bladed on traction utilization and knee mechanics of male and female participants during lateral cutting before and after fatigue progression. College-aged soccer participants (10 males, 10 females) performed 2 data collections in cleated footwear of different stud shapes. Lower limb kinetics and kinematics were compared between cleats and across fatigue states. No interaction effects were found on knee mechanics, though main effects of sex and fatigue were observed. A 3-way interaction on the rate of traction utilized at initial contact was found, demonstrating the influence of fatigue and cleat on sex-specific ground interactions. Future works are warranted to understand the effect of high-performance product on female mechanics.
Lumbar spine passive stiffness (LSPS) has been theorized to be a necessary source of stability for the vertebral column. However, the degree that LSPS plays in maintaining spinal stability has yet to be investigated. Trunk moment of inertia has been linked to LSPS, suggesting that an optimal LSPS value may exist. Determining trunk moment of inertia and LSPS allows the trunk to be modeled as an oscillatory system. Therefore, the current work aimed to determine if LSPS can be applied to infer spinal stability by comparing the predicted natural frequency of the trunk to the mean power frequency of lumbopelvic sway. Twenty participants completed a 5-minute standing trial. The mean power frequency of their lumbopelvic angle sway was quantified using a Fourier transform. The natural frequency of the trunk was estimated using anthropometric measures. A significant relationship was observed between the natural frequency of lumbopelvic angle sway and the natural frequency of the trunk, suggesting that trunk kinematics can be modeled using inputs of LSPS and trunk moment of inertia. Such findings reinforce the importance of LSPS in maintaining the stability of the spine and provide a novel avenue for spinal stability to be investigated.
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.
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.
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.
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.
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.
