Biomechanical Investigation of Lower Limbs during Slope Transformation Running with Different Longitudinal Bending Stiffness Shoes.

BACKGROUND: During city running or marathon races, shifts in level ground and up-and-down slopes are regularly encountered, resulting in changes in lower limb biomechanics. The longitudinal bending stiffness of the running shoe affects the running performance. PURPOSE: This research aimed to investigate the biomechanical changes in the lower limbs when transitioning from level ground to an uphill slope under different longitudinal bending stiffness (LBS) levels in running shoes. METHODS: Fifteen male amateur runners were recruited and tested while wearing three different LBS running shoes. The participants were asked to pass the force platform with their right foot at a speed of 3.3 m/s ± 0.2. Kinematics data and GRFs were collected synchronously. Each participant completed and recorded ten successful experiments per pair of shoes. RESULTS: The range of motion in the sagittal of the knee joint was reduced with the increase in the longitudinal bending stiffness. Positive work was increased in the sagittal plane of the ankle joint and reduced in the keen joint. The negative work of the knee joint increased in the sagittal plane. The positive work of the metatarsophalangeal joint in the sagittal plane increased. CONCLUSION: Transitioning from running on a level surface to running uphill, while wearing running shoes with high LBS, could lead to improved efficiency in lower limb function. However, the higher LBS of running shoes increases the energy absorption of the knee joint, potentially increasing the risk of knee injuries. Thus, amateurs should choose running shoes with optimal stiffness when running.

Effect of forward and backward sloped support surfaces on postural equilibrium and ankle muscles activity.

INTRODUCTION: Although sloped surfaces are common in daily living, most studies of body balance are carried out on flat surfaces, and few data are available for sloping angles below 14°. OBJECTIVES: The purpose of this study was to explore the effect of forward and backward sloping surfaces at 7° and 15° on postural equilibrium and the activity of flexor/extensor ankle muscles. METHODS: Fifteen healthy subjects (8 males and 7 females) (27.67 ± 3.9 years) underwent a posturographic examination associated with a surface electromyogram (EMG) of tibialis anterior (TA), soleus (Sol) and gastrocnemius medialis (GasM) under five conditions of support inclination: 0° (H0), backward inclination at 7° and 15° (DF7 and DF15), forward inclination at 7° and 15° (PF7 and PF15). RESULTS: Results showed that the center of pressure (CP) was shifted according to the surface slope, with a forward move in PF7 (p <0.001) and PF15 (p <0.001) and a backward move in DF7 (p <0.01) and in DF15 (p <0.001). The mean displacement of the CP along the anterior-posterior axis (Xm) was increased in DF15 (p <0.01) relative to the H0 condition but reduced in PF7 (p <0.01). The normalized EMG revealed higher values when the muscles were in a shortened position (PF7 for Sol, p <0.05; PF15 for GasM, p <0.01; DF15 for TA, p<0.01) and lower values of GasM and Sol when lengthened (DF15, p <0.05). CONCLUSION: Our findings indicate that standing on a backward sloped surface impairs body balance, while low-angle forward sloped surfaces might improve postural stability. Muscular activity variations of the ankle flexors/extensors, which are stretched or shortened, also seem to be related to the length-tension relationship of skeletal muscles.

Relationship between ankle dorsiflexion range of motion and sprinting and jumping ability in young athletes.

OBJECTIVES: To investigate the relationship between predicted risk of injury based on the dichotomous classification of the weight-bearing lunge (WBL) test scores and variables related to jumping and sprinting ability in young athletes. Furthermore, to compare the impact of the classical dichotomous classification versus a more specific quartile subdivision of the WBL test scores on the explored variables. DESIGN: Cross-sectional study. PARTICIPANTS: 125 healthy athletes (mean age 10.38 (SD = 2.28) years) were recruited. MAIN OUTCOME MEASURES: Ankle dorsiflexion was evaluated with the WBL test, jumping distance with the standing long jump (SLJ) test, and maximal running speed with the 14-m and 28-m sprint test. RESULTS: Athletes with WBL test scores lower than 10 cm exhibited significantly poorer results for the SLJ test as well as lower 14-m and 28-m sprint times than those with WBL test scores higher than 10 cm (p < 0.05). Likewise, when WBL test scores were subdivided by quartiles, a positive trend between range of motion and improved performance was shown. CONCLUSIONS: Reduced ankle dorsiflexion mobility may affect sprinting and jumping ability in young athletes. In addition, a more detailed classification of ankle restriction by quartiles is proposed in this study in order to prevent injury and enhance athletic performance.

Single-legged landing behavior of high school basketball players with chronic ankle instability.

OBJECTIVES: Anterior cruciate ligament injury is one of the most serious ligamentous injuries. The purpose is to compare the impact of the ankle joint on the knee during landing between athletes with chronic instability and a control group (coper group) and to verify the effects of the kinetic chain from other joints. DESIGN: Prospective study. SETTING: High school basketball. PARTICIPANTS: Participants were 62 female high school basketball players who had participated in team sports for >6 months. MAIN OUTCOME MEASURES: Player joint angles, movements, and moments. RESULTS: The knee valgus moment was significantly higher in the chronic ankle instability group than in the coper group (20%-60% [p < 0.01]; 80%-100% [p < 0.05]) during landing motion. The knee valgus moment was also significantly higher during the change from the maximum knee joint flexion position to the maximum extension (p < 0.05). In addition, the landing motions of the chronic instability group may have utilized suboptimal compensatory motor strategy on the sagittal plane, depending heavily on the knee joint's abduction moment. CONCLUSIONS: Our findings indicate that the chronic ankle instability group uses a different landing strategy pattern than the coper group by changing the joint moment and joint angle during landing, which may increase the risk of anterior cruciate ligament injury.

Effects of ankle joint mobilization on dynamic balance muscle activity and dynamic balance in persons with chronic ankle instability - Feasibility of a cross-over study.

INTRODUCTION: Studies with focus on effects of manual therapy techniques on postural control and muscle activity in patients with chronic ankle instability (are lacking. The purpose of this study was to evaluate the feasibility of a planned cross-over study to assess efficacy of manual therapy techniques applications in patients with chronic ankle instability. METHODS: This feasibility study used a randomized controlled, blinded assessor cross-over design. Criteria of success under evaluation were adherence and attrition rates and adverse events. while preliminary treatment effects of manual therapy techniques on muscular activity (measured by surface electromyography) and on dynamic balance (measured by time to stabilization test) were secondary aims. RESULTS: Thirteen participants (mean age: 24.4 ± 3.8 years) with chronic ankle instability volunteered in this feasibility study. Success criteria showed a high adherence (98.7%) and low attrition (0%). No missing data were reported but four out of 26 data sets could not be used for statistical analysis because of non-readability of the recorded data. Preliminary treatment effect showed divergent results for surface electromyography and time to stabilization. One significant result (p = 0.03, ES = 1.48) in peroneus longus muscle activity after jump landing between 30 and 60 ms could be determined. CONCLUSIONS: This study showed that the study protocol is feasible but should be modified by offering participants the opportunity to familiarize to the jumps and to the test repetitions. This study generates better understanding of manual therapy techniques for patients with chronic ankle instability.

Reductions in rearfoot eversion posture due to proximal muscle strengthening are dependent on foot-ankle varus alignment.

BACKGROUND: Strengthening the hip and trunk muscles may decrease foot pronation in upright standing due to expected increases in hip passive torque and lower-limb external rotation. However, considering the increased pronation caused by a more varus foot-ankle alignment, subjects with more varus may experience smaller or no postural changes after strengthening. OBJECTIVE: To investigate the effects of hip and trunk muscle strengthening on lower-limb posture during upright standing and hip passive torque of women with more and less varus alignment. METHODS: This nonrandomized controlled experimental study included 50 young, able-bodied women. The intervention group (n = 25) performed hip and trunk muscle strengthening exercises, and the control group (n = 25) maintained their usual activities. Each group was split into two subgroups: those with more and less varus alignment. Hip, shank, and rearfoot-ankle posture and hip passive external rotation torque were evaluated. Mixed analyses of variance and preplanned contrasts were used to assess prepost changes and between-group differences (α = 0.05). RESULTS: The less-varus subgroup of the intervention group had a reduced rearfoot eversion posture (P = 0.02). No significant changes were observed in the less-varus subgroup of the control group (P = 0.31). There were no significant differences in posture between the control and intervention groups when varus was not considered (P ≥ 0.06). The intervention group had increased hip passive torque (P = 0.001) compared to the control group, independent of varus alignment. CONCLUSION: Despite the increases in hip passive torque, the rearfoot eversion posture was reduced only in women with a less-varus alignment. Having more foot-ankle varus may prevent eversion reductions.

Feature Decoupling for Multimodal Locomotion and Estimation of Knee and Ankle Angles Implemented by Multi-Model Fusion.

Many challenges exist in the study of using orthotics, exoskeletons or exosuits as tools for rehabilitation and assistance of healthy people in daily activities due to the requirements of portability and safe interaction with the user and the environment. One approach to dealing with these challenges is to design a control system that can be deployed in a portable device to identify the relationships that exist between the gait variables and gait cycle for different locomotion modes. In order to estimate the knee and ankle angles in the sagittal plane for different locomotion modes, a novel multimodal feature-decoupled kinematic estimation system consisting of a multimodal locomotion classifier and an optimal joint angle estimator is proposed in this paper. The multi-source information output from different conventional primary models are fused by assigning the non-fixed weight. To improve the performance of the primary models, a data augmentation module based on the time-frequency domain analysis method is designed. The results show that the inclusion of the data augmentation module and multi-source information fusion modules has improved the classification accuracy to 98.56% and kinematic estimation performance (PCC) to 0.904 (walking), 0.956 (running), 0.899 (stair ascent), 0.851 (stair descent), respectively. The kinematic estimation quality is generally higher for faster speed (running) or proximal joint (knee) compared to other modes and ankle. The limitations and advantages of the proposed approach are discussed. Based on our findings, the multimodal kinematic estimation system has potential in facilitating the deployment for human-in-loop control of lower-limb intelligent assistive devices.

A Biomechanical Comparison Between a High and Low Barbell Placement on Net Joint Moments, Kinematics, Muscle Forces, and Muscle-Specific Moments in 3 Repetition Maximum Back Squats.

ABSTRACT: Larsen, S, de Zee, M, Kristiansen, EL, and van den Tillaar, R. A biomechanical comparison between a high and low barbell placement on net joint moments, kinematics, muscle forces, and muscle-specific moments in 3 repetition maximum back squats. J Strength Cond Res 38(7): 1221-1230, 2024-This study aimed to investigate the impact of a high barbell vs. low barbell placement on net joint moments, muscle forces, and muscle-specific moments in the lower extremity joints and muscles during maximum back squats. Twelve recreationally trained men (age = 25.3 ± 2.9 years, height = 1.79 ± 7.7 m, and body mass = 82.8 ± 6.9 kg) volunteered for the study. A marker-based motion capture system and force plate data were used to calculate the net joint moments, and individual muscle forces were estimated using static optimization. Muscle forces were multiplied by their corresponding internal moment arms to determine muscle-specific moments. Statistical parametric mapping was used to analyze the effect of barbell placement as time-series data during the concentric phase. The 3 repetition maximum barbell load lifted by the subjects was 129.1 ± 13.4 kg and 130.2 ± 12.7 kg in the high bar and low bar, which were not significantly different from each other. Moreover, no significant differences were observed in net joint moments, muscle forces, or muscle-specific moments for the hip, knee, or ankle joint between the low- and high bar placements. The findings of this study suggest that barbell placement plays a minor role in lower extremity muscle forces and moment-specific moments when stance width is standardized, and barbell load lifted does not differ between barbell placements among recreationally resistance-trained men during maximal back squats. Therefore, the choice of barbell placement should be based on individual preference and comfort.

The Effect of Sensor Feature Inputs on Joint Angle Prediction across Simple Movements.

The use of wearable sensors, such as inertial measurement units (IMUs), and machine learning for human intent recognition in health-related areas has grown considerably. However, there is limited research exploring how IMU quantity and placement affect human movement intent prediction (HMIP) at the joint level. The objective of this study was to analyze various combinations of IMU input signals to maximize the machine learning prediction accuracy for multiple simple movements. We trained a Random Forest algorithm to predict future joint angles across these movements using various sensor features. We hypothesized that joint angle prediction accuracy would increase with the addition of IMUs attached to adjacent body segments and that non-adjacent IMUs would not increase the prediction accuracy. The results indicated that the addition of adjacent IMUs to current joint angle inputs did not significantly increase the prediction accuracy (RMSE of 1.92° vs. 3.32° at the ankle, 8.78° vs. 12.54° at the knee, and 5.48° vs. 9.67° at the hip). Additionally, including non-adjacent IMUs did not increase the prediction accuracy (RMSE of 5.35° vs. 5.55° at the ankle, 20.29° vs. 20.71° at the knee, and 14.86° vs. 13.55° at the hip). These results demonstrated how future joint angle prediction during simple movements did not improve with the addition of IMUs alongside current joint angle inputs.

The ankle dorsiflexion kinetics demand to increase swing phase foot-ground clearance: implications for assistive device design and energy demands.

BACKGROUND: The ankle is usually highly effective in modulating the swing foot's trajectory to ensure safe ground clearance but there are few reports of ankle kinetics and mechanical energy exchange during the gait cycle swing phase. Previous work has investigated ankle swing mechanics during normal walking but with developments in devices providing dorsiflexion assistance, it is now essential to understand the minimal kinetic requirements for increasing ankle dorsiflexion, particularly for devices employing energy harvesting or utilizing lighter and lower power energy sources or actuators. METHODS: Using a real-time treadmill-walking biofeedback technique, swing phase ankle dorsiflexion was experimentally controlled to increase foot-ground clearance by 4 cm achieved via increased ankle dorsiflexion. Swing phase ankle moments and dorsiflexor muscle forces were estimated using AnyBody modeling system. It was hypothesized that increasing foot-ground clearance by 4 cm, employing only the ankle joint, would require significantly higher dorsiflexion moments and muscle forces than a normal walking control condition. RESULTS: Results did not confirm significantly increased ankle moments with augmented dorsiflexion, with 0.02 N.m/kg at toe-off reducing to zero by the end of swing. Tibialis Anterior muscle force incremented significantly from 2 to 4 N/kg after toe-off, due to coactivation with the Soleus. To ensure an additional 4 cm mid swing foot-ground clearance, an estimated additional 0.003 Joules/kg is required to be released immediately after toe-off. CONCLUSION: This study highlights the interplay between ankle moments, muscle forces, and energy demands during swing phase ankle dorsiflexion, offering insights for the design of ankle assistive technologies. External devices do not need to deliver significantly greater ankle moments to increase ankle dorsiflexion but, they should offer higher mechanical power to provide rapid bursts of energy to facilitate quick dorsiflexion transitions before reaching Minimum Foot Clearance event. Additionally, for ankle-related bio-inspired devices incorporating artificial muscles or humanoid robots that aim to replicate natural ankle biomechanics, the inclusion of supplementary Tibialis Anterior forces is crucial due to Tibialis Anterior and Soleus co-activation. These design strategies ensures that ankle assistive technologies are both effective and aligned with the biomechanical realities of human movement.

Surface electromyography analysis of ankle flexor and extensor activity under different standing stability levels.

Background: To observe the activation strategies of the ankle muscles using surface electromyography (sEMG) during single-leg standing (SLS) and both-leg standing (BLS) on flat ground (FG), soft mat (SM), and BOSU ball (BB) surfaces. Methods: Thirty healthy young adults participated in the study. The muscle activities of the tibialis anterior (TA) and gastrocnemius medial (GM) were measured on the three surfaces during SLS and BLS. Electromyographic evaluations of the TA and GM were recorded during maximum voluntary isometric contractions (MVIC). Muscle activation was evaluated using MVIC%, and muscle co-contraction was evaluated using the co-contraction index (CI). Results: A statistically significant increase was observed in the MVIC% of the TA, GM, and CI on the three surfaces during SLS compared to BLS, except for the comparison of CI on BB between SLS and BLS (t = -1.35, p = 0.19). The MVIC% of the TA and GM during SLS and BLS on BB was significantly increased in comparison with FG and SM. The CI during BLS on BB increased compared to FG (t = 3.19, p < 0.01) and SM (t = 4.64, p < 0.01). The CI during BLS on SM (t = -1.46, p = 0.15) decreased when compared to FG but without statistical significance. Conclusions: SLS and unstable surfaces can induce greater muscle activation, and SLS can have a greater influence on ankle muscles.

Design and preliminary verification of a novel powered ankle-foot prosthesis: From the perspective of lower-limb biomechanics compared with ESAR foot.

A novel powered ankle-foot prosthesis is designed. The effect of wearing the novel prosthesis and an energy-storage-and-return (ESAR) foot on lower-limb biomechanics is investigated to preliminarily evaluate the design. With necessary auxiliary materials, a non-amputated subject (a rookie at using prostheses) is recruited to walk on level ground with an ESAR and the novel powered prostheses separately. The results of the stride characteristics, the ground reaction force (GRF) components, kinematics, and kinetics in the sagittal plane are compared. Wearing the powered prosthesis has less prolongation of the gait cycle on the unaffected side than wearing the ESAR foot. Wearing ESAR or proposed powered prostheses influences the GRF, kinematics, and kinetics on the affected and unaffected sides to some extent. Thereinto, the knee moment on the affected side is influenced most. Regarding normal walking as the reference, among the total of 15 indexes, the influences of wearing the proposed powered prosthesis on six indexes on the affected side (ankle's/knee's/hip's angles, hip's moment, and Z- and X-axis GRF components) and five indexes on the unaffected side (ankle's/knee's/hip's angles and ankle's/hip's moments) are slighter than those of wearing the ESAR foot. The influences of wearing the powered prosthesis on two indexes on the unaffected side (knee's moment and X-axis GRF component) are similar to those of wearing the ESAR foot. The greatest improvement of wearing the powered prosthesis is to provide further plantarflexion after reaching the origin of the ankle joint before toe-off, which means that the designed powered device can provide further propulsive power for the lifting of the human body's centre of gravity during walking on level ground. The results demonstrate that wearing the novel powered ankle-foot prosthesis benefits the rookie in recovering the normal gait more than wearing the ESAR foot.

Asymmetry in kinematics of dominant/nondominant lower limbs in central and lateral positioned college and sub-elite soccer players.

Change of direction, stops, and pivots are among the most common non-contact movements associated with anterior cruciate ligament (ACL) injuries in soccer. By observing these dynamic movements, clinicians recognize abnormal kinematic patterns that contribute to ACL tears such as increased knee valgus or reduced knee flexion. Different motions and physical demands are observed across playing positions, which may result in varied lower limb kinematic patterns. In the present study, 28 college and sub-elite soccer players performed four dynamic motions (change of direction with and without ball, header, and instep kick) with the goal of examining the effect of on-field positioning, leg dominance, and gender in lower body kinematics. Motion capture software monitored joint angles in the knee, hip, and ankle. A three-way ANOVA showed significant differences in each category. Remarkably, centrally positioned players displayed significantly greater knee adduction (5° difference, p = 0.013), hip flexion (9° difference, p = 0.034), hip adduction (7° difference, p = 0.016), and dorsiflexion (12° difference, p = 0.022) when performing the instep kick in comparison to their laterally positioned counterparts. These findings suggest that central players tend to exhibit a greater range of motion when performing an instep kicking task compared to laterally positioned players. At a competitive level, this discrepancy could potentially lead to differences in lower limb muscle development among on-field positions. Accordingly, it is suggested to implement position-specific prevention programs to address these asymmetries in lower limb kinematics, which can help mitigate dangerous kinematic patterns and consequently reduce the risk of ACL injury in soccer players.

Role of midsole hollow structure in energy storage and return in running shoes.

Understanding the relationship between footwear features and their potential influence on running performance can inform the ongoing innovation of running footwear, aimed at pushing the limits of humans. A notable shoe feature is hollow structures, where an empty space is created in the midsole. Presently, the potential biomechanical effect of the hollow structures on running performance remains unknown. We investigated the role of hollow structures through quantifying the magnitude and timing of foot and footwear work. Sixteen male rearfoot runners participated in an overground running study in three shoe conditions: (a) a shoe with a hollow structure in the forefoot midsole (FFHS), (b) the same shoe without any hollow structure (Filled-FFHS) and (c) a shoe with a hollow structure in the midfoot midsole (MFHS). Distal rearfoot power was used to quantify the net power generated by foot and footwear together. The magnitude and timing of distal rearfoot work and ankle joint work were compared across shoe conditions. The results indicated that MFHS can significantly (p = 0.024) delay distal rearfoot energy return (3.4 % of stance) when compared to Filled-FFHS. Additionally, FFHS had the greatest positive (0.425 J/kg) and negative (-0.383 J/kg) distal rearfoot work, and the smallest positive (0.503 J/kg) and negative (-0.477 J/kg) ankle joint work among the three conditions. This showed that the size and location of the midsole hollow structure can affect timing and magnitude of energy storage and return. The forefoot hollow shoe feature can effectively increase distal rearfoot work and reduce ankle joint work during running.

The effect of including a mobile arch, toe joint, and joint coupling on predictive neuromuscular simulations of human walking.

Predictive neuromuscular simulations are a powerful tool for studying the biomechanics of human walking, and deriving design criteria for technical devices like prostheses or biorobots. Good agreement between simulation and human data is essential for transferability to the real world. The human foot is often modeled with a single rigid element, but knowledge of how the foot model affects gait prediction is limited. Standardized procedures for selecting appropriate foot models are lacking. We performed 2D predictive neuromuscular simulations with six different foot models of increasing complexity to answer two questions: What is the effect of a mobile arch, a toe joint, and the coupling of toe and arch motion through the plantar fascia on gait prediction? and How much of the foot's anatomy do we need to model to predict sagittal plane walking kinematics and kinetics in good agreement with human data? We found that the foot model had a significant impact on ankle kinematics during terminal stance, push-off, and toe and arch kinematics. When focusing only on hip and knee kinematics, rigid foot models are sufficient. We hope our findings will help guide the community in modeling the human foot according to specific research goals and improve neuromuscular simulation accuracy.

Test-retest reliability of gastrocnemius medialis fascicle force-length relationship.

Fascicle force-length relationship is one major basic mechanical property of skeletal muscle, subsequently influencing movement mechanics. While force-length properties are increasingly described through ultrafast ultrasound imaging, their test-retest reliability remains unknown. Using ultrafast ultrasound, and electrically evoked contractions at various ankle angles, gastrocnemius medialis fascicle force-length relationship was assessed twice, few days apart, in sixteen participants. The test-retest reliability of the resulting fascicle force-length relationship key parameters - i.e., maximal force (Fmax), and optimal fascicle length (L0) - was evaluated considering (i) all the trials obtained at each ankle joint and (ii) the mean of the two trials obtained at each tested angle. Considering all trials, L0 indicated a 'high' test-retest reliability, with intra-class correlation coefficients (ICC) of 0.89 and Fmax a 'moderate' reliability (ICC = 0.71), while when averaging the two trials L0 reliability was 'very-high' (ICC = 0.91), and Fmax reliability 'moderate' (ICC = 0.73). All values of coefficient of variation and standard error of measurement were low, i.e., ≤7.7 % and ≤0.35 cm for L0 and ≤3.4 N for Fmax, respectively. Higher absolute reliability was reported for L0 than Fmax, with better reliability when averaging the two trials at each angle. All these parameters, in accordance with the limit of agreement, demonstrated that L0 and Fmax test-retest reliability is acceptable, particularly when averaging multiple points obtained at a given angle. Interestingly, the shape of the fascicle force-length relationship is more variable. Therefore, L0 and Fmax can be used to compare between days-effects following an intervention, while a comparison of fascicle operating lengths may require more precautions.

Effects of 6 weeks of whole-body vibration training on ankle motor control: a randomized controlled trial.

BACKGROUND: Interventions on ankle motor control are important to prevent recurrent ankle sprains. Training using whole-body vibration may easily and effectively improve ankle motor control, but the effects have not been investigated. Therefore, this study aimed to clarify the effects of 6 weeks of training with whole-body vibration on ankle motor control in a dynamic movement task among healthy participants. METHODS: Twenty healthy university students (6 males and 14 females) were randomly allocated to whole-body vibration training and control groups, with 10 participants in each group. The training was performed twice a week for 6 weeks in both groups. Primary outcome was mean ankle angular jerk cost in the star excursion balance test. Secondary outcomes were maximum ankle motion angle and maximum reach distance in the star excursion balance test, ankle proprioception, and range of ankle dorsiflexion motion in the loaded position. RESULTS: There was a significant group × period (pre- and postintervention) interaction for mean ankle angular jerk cost in the direction of ankle abduction/adduction during posterolateral reaching, which was significantly lower at postintervention than that at preintervention in the whole-body vibration group In the whole-body vibration group, the maximum ankle dorsiflexion motion angle during anterior and posterolateral reaching was significantly higher at postintervention than that at preintervention. CONCLUSIONS: Training with whole-body vibration improves ankle motor control in dynamic movement tasks, although the direction of reach and plane of motion are limited. Additionally, training with whole-body vibration is also effective in increasing the ankle dorsiflexion angle during dynamic movement tasks.

Effect of age on ankle biomechanics and tibial compression during stair descent.

BACKGROUND: Stress fracture is a concern among older adults, as age-related decrements in ankle neuromuscular function may impair their ability to attenuate tibial compressive forces experienced during daily locomotor tasks, such as stair descent. Yet, it is unknown if older adults exhibit greater tibial compression than their younger counterparts when descending stairs. RESEARCH QUESTION: Do older adults exhibit differences in ankle biomechanics that alter their tibial compression during stair descent compared to young adults, and is there a relation between tibial compression and specific changes in ankle biomechanics? METHODS: Thirteen young (18-25 years) and 13 older (> 65 years) adults had ankle joint biomechanics and tibial compression quantified during a stair descent. Discrete ankle biomechanics (peak joint angle and moment, and joint stiffness) and tibial compression (maximum and impulse) measures were submitted to an independent t-test, while ankle joint angle and moment, and tibial compression waveforms were submitted to an independent statistical parametric mapping t-test to determine group differences. Pearson correlation coefficients (r) determined the relation between discrete ankle biomechanics and tibial compression measures for all participants, and each group. RESULTS: Older adults exhibited smaller maximum tibial compression (p = 0.004) from decreases in peak ankle joint angle and moment between 17 % and 34 % (p = 0.035), and 20-31 % of stance (p < 0.001) than young adults. Ankle biomechanics exhibited a negligible to weak correlation with tibial compression for all participants, with peak ankle joint moment and maximum tibial compression (r = -0.48 ±â€¯0.32) relation the strongest. Older adults typically exhibited a stronger relation between ankle biomechanics and tibial compression (e.g., r = -0.48 ±â€¯0.47 vs r = -0.27 ±â€¯0.52 between peak ankle joint moment and maximum tibial compression). SIGNIFICANCE: Older adults altered ankle biomechanics and decreased maximum tibial compression to safely execute the stair descent. Yet, specific alterations in ankle biomechanics could not be identified as a predictor of changes in tibial compression.

Hindfoot kinematics and kinetics - A combined in vivo and in silico analysis approach.

BACKGROUND: The complex anatomical structure of the foot-ankle imposes challenges to accurately quantify detailed hindfoot kinematics and estimate musculoskeletal loading parameters. Most systems used to capture or estimate dynamic joint function oversimplify the anatomical structure by reducing its complexity. RESEARCH QUESTION: Can four dimensional computed tomography (4D CT) imaging in combination with an innovative foot manipulator capture in vivo hindfoot kinematics during a simulated stance phase of walking and can talocrural and subtalar articular joint mechanics be estimated based on a detailed in silico musculoskeletal foot-ankle model. METHODS: A foot manipulator imposed plantar/dorsiflexion and inversion/eversion representing a healthy stance phase of gait in 12 healthy participants while simultaneously acquiring 4D CT images. Participant-specific 3D hindfoot rotations and translations were calculated based on bone-specific anatomical coordinate systems. Articular cartilage contact area and contact pressure of the talocrural and subtalar joints were estimated using an extended foot-ankle model updated with an elastic foundation contact model upon prescribing the participant-specific rotations measured in the 4D CT measurement. RESULTS: Plantar/dorsiflexion predominantly occurred at the talocrural joint (RoM 15.9±3.9°), while inversion/eversion (RoM 5.9±3.9°) occurred mostly at the subtalar joint, with the contact area being larger at the subtalar than at the talocrural joint. Contact pressure was evenly distributed between the talocrural and subtalar joint at the beginning of the simulated stance phase but was then redistributed from the talocrural to the subtalar joint with increasing dorsiflexion. SIGNIFICANCE: In a clinical case study, the healthy participants were compared with four patients after surgically treaded intra-articular calcaneal fracture. The proposed workflow was able to detect small but meaningful differences in hindfoot kinematics and kinetics, indicative of remaining hindfoot pathomechanics that may influence the onset and progression of degenerative joint diseases.

BiLSTM-Based Joint Torque Prediction From Mechanomyogram During Isometric Contractions: A Proof of Concept Study.

Quantifying muscle strength is an important measure in clinical settings; however, there is a lack of practical tools that can be deployed for routine assessment. The purpose of this study is to propose a deep learning model for ankle plantar flexion torque prediction from time-series mechanomyogram (MMG) signals recorded during isometric contractions (i.e., a similar form to manual muscle testing procedure in clinical practice) and to evaluate its performance. Four different deep learning models in terms of model architecture (based on a stacked bidirectional long short-term memory and dense layers) were designed with different combinations of the number of units (from 32 to 512) and dropout ratio (from 0.0 to 0.8), and then evaluated for prediction performance by conducting the leave-one-subject-out cross-validation method from the 10-subject dataset. As a result, the models explained more variance in the untrained test dataset as the error metrics (e.g., root-mean-square error) decreased and as the slope of the relationship between the measured and predicted joint torques became closer to 1.0. Although the slope estimates appear to be sensitive to an individual dataset, >70% of the variance in nine out of 10 datasets was explained by the optimal model. These results demonstrated the feasibility of the proposed model as a potential tool to quantify average joint torque during a sustained isometric contraction.