Effects of gait retraining using minimalist shoes on the medial gastrocnemius muscle-tendon unit behavior and dynamics during running.

The effects of a 12-week gait retraining program on the adaptation of the medial gastrocnemius (MG) and muscle-tendon unit (MTU) were investigated. 26 runners with a rearfoot strike pattern (RFS) were randomly assigned to one of two groups: gait retraining (GR) or control group (CON). MG ultrasound images, marker positions, and ground reaction forces (GRF) were collected twice during 9 km/h of treadmill running before and after the intervention. Ankle kinetics and the MG and MTU behavior and dynamics were quantified. Runners in the GR performed gradual 12-week gait retraining transitioning to a forefoot strike pattern. After 12-week, (1) ten participants in each group completed the training; eight participants in GR transitioned to non-RFS with reduced foot strike angles; (2) MG fascicle contraction length and velocity significantly decreased after the intervention for both groups, whereas MG forces increased after intervention for both groups; (3) significant increases in MTU stretching length for GR and peak MTU recoiling velocity for both groups were observed after the intervention, respectively; (4) no significant difference was found for all parameters of the series elastic element. Gait retraining might potentially influence the MG to operate at lower fascicle contraction lengths and velocities and produce greater peak forces. The gait retraining had no effect on SEE behavior and dynamics but did impact MTU, suggesting that the training was insufficient to induce mechanical loading changes on SEE behavior and dynamics.

Effects of 12-week gait retraining on plantar flexion torque, architecture, and behavior of the medial gastrocnemius in vivo.

Objective: This study aims to explore the effects of 12-week gait retraining (GR) on plantar flexion torque, architecture, and behavior of the medial gastrocnemius (MG) during maximal voluntary isometric contraction (MVIC). Methods: Thirty healthy male rearfoot strikers were randomly assigned to the GR group (n = 15) and the control (CON) group (n = 15). The GR group was instructed to wear minimalist shoes and run with a forefoot strike pattern for the 12-week GR (3 times per week), whereas the CON group wore their own running shoes and ran with their original foot strike pattern. Participants were required to share screenshots of running tracks each time to ensure training supervision. The architecture and behavior of MG, as well as ankle torque data, were collected before and after the intervention. The architecture of MG, including fascicle length (FL), pennation angle, and muscle thickness, was obtained by measuring muscle morphology at rest using an ultrasound device. Ankle torque data during plantar flexion MVIC were obtained using a dynamometer, from which peak torque and early rate of torque development (RTD50) were calculated. The fascicle behavior of MG was simultaneously captured using an ultrasound device to calculate fascicle shortening, fascicle rotation, and maximal fascicle shortening velocity (Vmax). Results: After 12-week GR, 1) the RTD50 increased significantly in the GR group (p = 0.038), 2) normalized FL increased significantly in the GR group (p = 0.003), and 3) Vmax increased significantly in the GR group (p = 0.018). Conclusion: Compared to running training, GR significantly enhanced the rapid strength development capacity and contraction velocity of the MG. This indicates the potential of GR as a strategy to improve muscle function and mechanical efficiency, particularly in enhancing the ability of MG to generate and transmit force as well as the rapid contraction capability. Further research is necessary to explore the effects of GR on MG behavior during running in vivo.

Effects of a 12-week gait retraining program on the Achilles tendon adaptation of habitually shod runners.

PURPOSE: This study investigated the effects of a 12-week gait retraining program on the morphological and mechanical properties of the Achilles tendon (AT) during running on the basis of real-time dynamic ultrasound imaging. METHODS: A total of 30 male recreational runners who were used to wearing cushioned shoes with a rearfoot strike (RFS) pattern were recruited. They were randomized into a retraining group (RG, n = 15) and a control group (CG, n = 15). The RG group was asked to run in five-fingered minimalist shoes with a forefoot strike (FFS) pattern, and the CG group was asked to keep their strike pattern. Three training sessions were performed per week. All the participants in RG uploaded running tracks obtained through a mobile application (.jpg) after each session for training supervision. The ground reaction force, kinematics, and kinetics of the ankle joint at 10 km/h were collected using an instrumented split-belt treadmill and a motion capture system. The morphological (length and cross-sectional area) and mechanical characteristics (force, stress, strain, etc.) of AT in vivo were recorded and calculated with a synchronous ultrasonic imaging instrument before and after the intervention. Repeated two-way ANOVA was used to compare the aforementioned parameters. RESULTS: A total of 28 participants completed the training. The strike angle of RG after training was significantly smaller than that before training and significantly smaller than that of CG after training (F (1, 13) = 23.068, p < 0.001, partial η2 = 0.640). The length (F (1, 13) = 10.086, p = 0.007, partial η2 = 0.437) and CSA (F (1, 13) = 7.475, p = 0.017, partial η2 = 0.365) of AT in RG increased after training. A significant main effect for time was observed for the time-to-peak AT force (F (1, 13) = 5.225, p = 0.040, partial η2 = 0.287), average (F (1, 13) = 7.228, p = 0.019, partial η2 = 0.357), and peak AT loading rate (F (1, 13) = 11.687, p = 0.005, partial η2 = 0.473). CONCLUSION: Preliminary evidence indicated that a 12-week gait retraining program could exert a beneficial effect on AT. 57% (8/14) runners in RG shifted from RFS to FFS pattern. Although not all runners were categorized as FFS pattern after the intervention, their foot strike angle was reduced. Retraining primarily positively promoted AT morphological properties (i.e., CSA and length) to strengthen AT capability for mechanical loading.

Mechanics of The Medial Gastrocnemius-Tendon Unit in Behaving more Efficiently in Habitual Non-Rearfoot Strikers than in Rearfoot Strikers during Running.

This study aims to quantify how habitual foot strike patterns would affect ankle kinetics and the behavior and mechanics of the medial gastrocnemius-tendon unit (MTU) during running. A total of 14 runners with non-rearfoot strike patterns (NRFS) and 15 runners with rearfoot strike patterns (RFS) ran on an instrumented treadmill at a speed of 9 km/h. An ultrasound system and a motion capture system were synchronously triggered to collect the ultrasound images of the medial gastrocnemius (MG) and marker positions along with ground reaction forces (GRF) during running. Ankle kinetics (moment and power) and MG/MTU behavior and mechanical properties (MG shortening length, velocity, force, power, MTU shortening/lengthening length, velocity, and power) were calculated. Independent t-tests were performed to compare the two groups of runners. Pearson correlation was conducted to detect the relationship between foot strike angle and the MTU behavior and mechanics. Compared with RFS runners, NRFS runners had 1) lower foot strike angles and greater peak ankle moments; 2) lower shortening/change length and contraction velocity and greater MG peak force; 3) greater MTU lengthening, MTU shortening length and MTU lengthening velocity and power; 4) the foot strike angle was positively related to the change of fascicle length, fascicle contraction length, and MTU shortening length during the stance phase. The foot strike angle was negatively related to the MG force and MTU lengthening power. The MG in NRFS runners appears to contract with greater force in relatively isometric behavior and at a slower shortening velocity. Moreover, the lengthening length, the lengthening velocity of MTU, and the MG force were greater in habitual NRFS runners, leading to a stronger stretch reflex response potentially.

Morphological and viscoelastic properties of the Achilles tendon in the forefoot, rearfoot strike runners, and non-runners in vivo.

The purpose of this study was to investigate the differences in the morphological and viscoelastic properties of the Achilles tendon (AT) among different groups (rearfoot strikers vs. forefoot strikers vs. non-runners). Thirty healthy men were recruited, including habitual forefoot strike runners (n = 10), rearfoot strike runners (n = 10), and individuals with no running habits (n = 10). The AT morphological properties (cross-sectional area and length) were captured by using an ultrasound device. The real-time ultrasound video of displacement changes at the medial head of the gastrocnemius and the AT junction during maximal voluntary isometric contraction and the plantar flexion moment of the ankle was obtained simultaneously by connecting the ultrasound device and isokinetic dynamometer via an external synchronisation box. The results indicated that male runners who habitually forefoot strike exhibited significantly lower AT hysteresis than male non-runners (p < 0.05). Furthermore, a greater peak AT force during maximal voluntary contraction was observed in forefoot strike male runners compared to that in male individuals with no running habits (p < 0.05). However, foot strike patterns were not related to AT properties in recreational male runners (p > 0.05). The lower AT hysteresis in male FFS runners implied that long-term forefoot strike patterns could enhance male-specific AT's ability to store and release elastic energy efficiently during running, resulting in a more effective stretch-shortening cycle. The greater peak AT force in male FFS runners indicated a stronger Achilles tendon.

Anodal transcranial direct current stimulation enhances ankle force control and modulates the beta-band activity of the sensorimotor cortex.

This study aimed to investigate the cortical responses to the ankle force control and the mechanism underlying changes in ankle force control task induced by transcranial direct current stimulation (tDCS). Sixteen young adults were recruited, and they completed the electroencephalogram (EEG) assessment and high-definition tDCS (HD-tDCS) sessions. Root mean square (RMS) error was used to evaluate ankle force control task performance. Spectral power analysis was conducted to extract the average power spectral density (PSD) in the alpha (8-13 Hz) and beta (13-30 Hz) bands for resting state and tasking (i.e. task-PSD). The ankle force control task induced significant decreases in alpha and beta PSDs in the central, left, and right primary sensorimotor cortex (SM1) and beta PSD in the central frontal as compared with the resting state. HD-tDCS significantly decreased the RMS and beta task-PSD in the central frontal and SM1. A significant association between the percent change of RMS and the percent change of beta task-PSD in the central SM1 after HD-tDCS was observed. In conclusion, ankle force control task activated a distributed cortical network mainly including the SM1. HD-tDCS applied over SM1 could enhance ankle force control and modulate the beta-band activity of the sensorimotor cortex.

Effects of a 12-week gait retraining program combined with foot core exercise on morphology, muscle strength, and kinematics of the arch: A randomized controlled trial.

Objective: This study aims to explore the effects of a 12-week gait retraining program combined with foot core exercise on arch morphology, arch muscles strength, and arch kinematics. Methods: A total of 26 male recreational runners with normal arch structure who used rear-foot running strike (RFS) were divided into the intervention group (INT group) and control group (CON group) (n = 13 in each group). The INT group performed a 12-week forefoot strike (FFS) training combined with foot core exercises. The CON group did not change the original exercise habit. Before and after the intervention, the arch morphology, as well as the strength of hallux flexion, lesser toe flexion, and the metatarsophalangeal joint (MPJ) flexors were measured in a static position, and changes in the arch kinematics during RFS and FFS running were explored. Results: After a 12-week intervention, 1) the normalized navicular height increased significantly in the INT group by 5.1% (p = 0.027, Cohen's d = 0.55); 2) the hallux absolute flexion and relative flexion of the INT group increased significantly by 20.5% and 21.7%, respectively (p = 0.001, Cohen's d = 0.59; p = 0.001, Cohen's d = 0.73), the absolute and relative strength of the MPJ flexors of the INT group were significantly improved by 30.7% and 32.5%, respectively (p = 0.006, Cohen's d = 0.94; p = 0.006, Cohen's d = 0.96); 3) and during RFS, the maximum arch angle of the INT group declined significantly by 5.1% (p < 0.001, Cohen's d = 1.49), the arch height at touchdown increased significantly in the INT group by 32.1% (p < 0.001, Cohen's d = 1.98). Conclusion: The 12-week gait retraining program combined with foot core exercise improved the arch in both static and dynamic positions with a moderate to large effect size, demonstrating the superiority of this combined intervention over the standalone interventions. Thus, runners with weak arch muscles are encouraged to use this combined intervention as an approach to enhance the arch.

Effects of intervention combining transcranial direct current stimulation and foot core exercise on sensorimotor function in foot and static balance.

OBJECTIVE: This study aimed to examine the effects of combining transcranial direct current stimulation (tDCS) and foot core exercise (FCE) on the sensorimotor function of the foot (i.e., toe flexor strength and passive ankle kinesthesia) and static balance. METHODS: In this double-blinded and randomized study, 30 participants were randomly assigned into two groups: tDCS combined with FCE and sham combined with FCE (i.e., control group). The participants received 2 mA stimulation for 20 min concurrently with FCE over 4 weeks (i.e., three sessions per week). After the first two groups completed the intervention, a reference group (FCE-only group) was included to further explore the placebo effects of sham by comparing it with the control group. Foot muscle strength, passive ankle kinesthesia, and static balance were assessed at baseline and after the intervention. RESULTS: Compared with the control group and baseline, tDCS combined with FCE could increase toe flexor strength (p < 0.001) and decrease the passive kinesthesia threshold of ankle eversion (p = 0.002). No significant differences in static balance were observed between tDCS + FCE and control groups. The linear regression models showed an association towards significance between the percent changes in metatarsophalangeal joint flexor strength and the anteroposterior average sway velocity of the center of gravity in one-leg standing with eyes closed following tDCS + FCE (r2 = 0.286; p = 0.057). The exploratory analysis also showed that compared with FCE alone, the sham stimulation did not induce any placebo effects during FCE. CONCLUSION: Participating in 4 weeks of intervention using tDCS in combination with FCE effectively enhances toe flexor strength and foot-ankle sensory function.

Effects of Barefoot and Shod on the In Vivo Kinematics of Medial Longitudinal Arch During Running Based on a High-Speed Dual Fluoroscopic Imaging System.

Shoes affect the biomechanical properties of the medial longitudinal arch (MLA) and further influence the foot's overall function. Most previous studies on the MLA were based on traditional skin-marker motion capture, and the observation of real foot motion inside the shoes is difficult. Thus, the effect of shoe parameters on the natural MLA movement during running remains in question. Therefore, this study aimed to investigate the differences in the MLA's kinematics between shod and barefoot running by using a high-speed dual fluoroscopic imaging system (DFIS). Fifteen healthy habitual rearfoot runners were recruited. All participants ran at a speed of 3 m/s ± 5% along with an elevated runway in barefoot and shod conditions. High-speed DFIS was used to acquire the radiographic images of MLA movements in the whole stance phase, and the kinematics of the MLA were calculated. Paired sample t-tests were used to compare the kinematic characteristics of the MLA during the stance phase between shod and barefoot conditions. Compared with barefoot, shoe-wearing showed significant changes (p < 0.05) as follows: 1) the first metatarsal moved with less lateral direction at 80%, less anterior translation at 20%, and less superiority at 10-70% of the stance phase; 2) the first metatarsal moved with less inversion amounting to 20-60%, less dorsiflexion at 0-10% of the stance phase; 3) the inversion/eversion range of motion (ROM) of the first metatarsal relative to calcaneus was reduced; 4) the MLA angles at 0-70% of the stance phase were reduced; 5) the maximum MLA angle and MLA angle ROM were reduced in the shod condition. Based on high-speed DFIS, the above results indicated that shoe-wearing limited the movement of MLA, especially reducing the MLA angles, suggesting that shoes restricted the compression and recoil of the MLA, which further affected the spring-like function of the MLA.

Influence of Shod and Barefoot Running on the In Vivo Kinematics of the First Metatarsophalangeal Joint.

The biomechanics of the first metatarsophalangeal joint (MTPJ) is affected by different shoe conditions. In the biomechanical research field, traditional skin marker motion capture cannot easily acquire the in vivo joint kinematics of the first MTPJ in shoes. Thus, the present study aims to investigate the differences of the first MTPJ's six-degree-of-freedom (6DOF) kinematics between shod and barefoot running by using a high-speed dual fluoroscopic imaging system (DFIS). In total, 15 healthy male runners were recruited. Computed tomography scans were taken from each participant's right foot for the construction of 3D models and local coordinate systems. Radiographic images were acquired at 100 Hz while the participants ran at a speed of 3 m/s ± 5% in shod and barefoot conditions along an elevated runway, and 6DOF kinematics of the first MTPJ were calculated by 3D-2D registration. Paired sample t-tests were used to compare the kinematic characteristics of the first MTPJ 6DOF kinematics during the stance phase between shod and barefoot conditions. Compared with barefoot, wearing shoes showed significant changes (p < 0.05): 1) the first MTPJ moved less inferior at 50% but moved less superior at 90 and 100% of the stance phase; 2) the peak medial, posterior, and superior translation of the first MTPJ significantly decreased in the shod condition; 3) the extension angle of the first MTPJ was larger at 30-60% but smaller at 90 and 100% of the stance phase; 4) the maximum extension angle and flexion/extension range of motion of the first MTPJ were reduced; and 5) the minimum extension and adduction angle of the first MTPJ was increased in the shod condition. On the basis of the high-speed DFIS, the aforementioned results indicated that wearing shoes limited the first MTPJ flexion and extension movement and increased the adduction angle, suggesting that shoes may affect the propulsion of the first MTPJ and increase the risk of hallux valgus.

Effects of 4 Weeks of High-Definition Transcranial Direct Stimulation and Foot Core Exercise on Foot Sensorimotor Function and Postural Control.

Objective: This study aimed to examine the effects of 4 weeks of high-definition transcranial direct current stimulation (HD-tDCS) and foot core exercise (FCE) on foot sensorimotor function (i.e., toe flexor strength and passive ankle kinesthesia) and postural control. Methods: In total, 36 participants were randomly assigned into three groups as follows: HD-tDCS, FCE, and the control group. A total of 12 training sessions were performed over 4 weeks (i.e., three sessions per week) in the laboratory. The HD-tDCS group received 20-min HD-tDCS with a current density of 2 mA, and the FCE group completed short foot exercise, towel curls, toe spread and squeeze, and balance board training. Participants in the control group just maintained the activities what they usually did and did not receive any interventions. Foot muscle strength, passive ankle kinesthesia, and postural control were assessed at baseline and post-intervention. Results: HD-tDCS induced a greater decrease in the percentage changes in the passive kinesthesia thresholds of ankle inversion (p < 0.001) and eversion (p = 0.013) than the control group. Compared with the control group, a significant increase in the percentage change in the metatarsophalangeal joint flexor strength was found in the HD-tDCS group (p = 0.008) and the FCE group (p = 0.027), and a significant increase in the percentage change in toe flexor strength was observed in the FCE group (p = 0.015). Moreover, FCE induced a greater reduction in the percent changes in the medial-lateral average center of gravity sway velocity in one-leg standing with eyes open (p = 0.033) and the anteroposterior average center of gravity sway velocity in one-leg standing with eyes closed (p < 0.001) than control. Conclusion: This study demonstrated that 4 weeks of HD-tDCS and FCE induced distinct benefits on foot sensorimotor function and the standing postural control performance in healthy young adults. HD-tDCS could improve the metatarsophalangeal joint flexor strength and the passive kinesthesia thresholds of ankle inversion and eversion. Meanwhile, FCE could also enhance foot muscle strength and enhance postural control performance in one-leg standing.

Exercise Effects on the Biomechanical Properties of the Achilles Tendon-A Narrative Review.

The morphological and mechanical properties (e.g., stiffness, stress, and force) of the Achilles tendon (AT) are generally associated with its tendinosis and ruptures, particularly amongst runners. Interest in potential approaches to reduce or prevent the risk of AT injuries has grown exponentially as tendon mechanics have been efficiently improving. The following review aims to discuss the effect of different types of exercise on the AT properties. In this review article, we review literature showing the possibility to influence the mechanical properties of the AT from the perspective of acute exercise and long-term training interventions, and we discuss the reasons for inconsistent results. Finally, we review the role of the habitual state in the AT properties. The findings of the included studies suggest that physical exercise could efficiently improve the AT mechanical properties. In particular, relatively long-term and low-intensity eccentric training may be a useful adjunct to enhance the mechanical loading of the AT.

Wearing Cushioning Shoes Reduce Load Rates More Effectively in Post-Fatigue than in Pre-Fatigue during Landings.

PURPOSE: this study aimed to investigate the footwear cushioning effects on impact forces and joint kinematics of the lower extremity during bipedal drop landings before and after acute exercise-induced fatigue protocol. METHODS: in this case, 15 male collegiate basketball athletes performed drop landings from a 60 cm platform wearing highly-cushioned shoes (HS) and less cushioned shoes (control shoes, CS) before and after acute fatigue-inducing exercises (i.e., shuttle run combined with multiple vertical jumps). Force plates and motion capturing systems were synchronised to measure ground reaction forces and kinematic data during drop landings. Maximum jump height was analysed with one-way ANOVA. Two-way repeated measure ANOVAs were performed on each of the tested variables to examine if there was significant main effects of shoe and fatigue as well as the interaction. The significance level was set to 0.05. RESULTS: rearfoot peak impact forces and loading rates significantly reduced when the participants wore HS in pre- and post-fatigue conditions. The peak loading rates in forefoot significantly reduced when HS were worn in post-fatigue. Compared with pre-fatigue, wearing HS contributed to with 24% and 13% reduction in forefoot and rearfoot peak loading rates, respectively, and the occurrence times of first and second peak impact forces and loading rates were much later. In the post-fatigue, a significant increase in the initial contact and minimum angles of the ankle were observed in HS compared with CS. CONCLUSION: these findings suggest that footwear cushioning can reduce landing-related rearfoot impact forces regardless of fatigue conditions. In a situation where the neuromuscular activity is reduced or absent such as post-fatigue wearing better cushioning shoes show superior attenuation, as indicated by lower forefoot and rearfoot impacts.

Effects of 12-week transition training with minimalist shoes on Achilles tendon loading in habitual rearfoot strike runners.

Minimalist shod runners have reported greater material and mechanical properties of the Achilles tendon (AT) due to increased loading than runners who wear more cushioned running shoes. This study aimed to investigate the effects of 12-week transition training from conventional shoes to minimalist shoes on AT loading in habitual rearfoot strike runners. Seventeen healthy male habitual rearfoot strikers completed 12-week transition training. They were instructed either to run in minimalist shoes with a forefoot strike pattern (MIN + FFS, n = 9) or run in minimalist shoes but were free to develop their strike pattern (MIN, n = 8). Ultrasound images were captured to determine the cross-sectional area of the AT. Sagittal plane ankle kinematics and ground reaction forces were recorded simultaneously to quantify ankle joint mechanics and AT loading. The strike angle significantly decreased in MIN + FFS after the transition training, indicating a flatter foot at initial contact, whereas no changes were observed in MIN. After training, a significant increase in peak plantarflexion moment was observed for MIN + FFS (15.4%) and MIN (7.6%). Significantly increased peak AT force, peak loading rate and peak stress were observed after training in both groups. Specifically, MIN + FFS had a greater increase in peak AT force (20.3% versus 10.1%), peak loading rate (37.2% versus 25.4%) and peak AT stress (13.7% versus 8.1%) than MIN. Furthermore, for both groups, there were no significant differences in the moment arm and cross-sectional area of the AT observed before and after 12 weeks of training. The results of this study suggested that it was insufficient to promote the morphological adaptation of the AT, but the mechanical loading of the AT was adapted during running after 12-week transition training with minimalist shoes in MIN + FFS and MIN. Preliminary evidence showed that a gradual transition to minimalist shoes with a forefoot strike pattern may be beneficial to the mechanical loading of the AT.

Sex Differences in the Morphological and Mechanical Properties of the Achilles Tendon.

BACKGROUND: Patients with Achilles tendon (AT) injuries are often engaged in sedentary work because of decreasing tendon vascularisation. Furthermore, men are more likely to be exposed to AT tendinosis or ruptures. These conditions are related to the morphological and mechanical properties of AT, but the mechanism remains unclear. This study aimed to investigate the effects of sex on the morphological and mechanical properties of the AT in inactive individuals. METHODS: In total, 30 inactive healthy participants (15 male participants and 15 female participants) were recruited. The AT morphological properties (cross-sectional area, thickness, and length) were captured by using an ultrasound device. The AT force-elongation characteristics were determined during isometric plantarflexion with the ultrasonic videos. The AT stiffness was determined at 50%-100% maximum voluntary contraction force. The AT strain, stress, and hysteresis were calculated. RESULTS: Male participants had 15% longer AT length, 31% larger AT cross-sectional area and 21% thicker AT than female participants (p < 0.05). The plantarflexion torque, peak AT force, peak AT stress, and AT stiffness were significantly greater in male participants than in female participants (p < 0.05). However, no significant sex-specific differences were observed in peak AT strain and hysteresis (p > 0.05). CONCLUSIONS: In physically inactive adults, the morphological properties of AT were superior in men but were exposed to higher stress conditions. Moreover, no significant sex-specific differences were observed in peak AT strain and hysteresis, indicating that the AT of males did not store and return elastic energy more efficiently than that of females. Thus, the mechanical properties of the AT should be maintained and/or improved through physical exercise.

Compression Garments Reduce Soft Tissue Vibrations and Muscle Activations during Drop Jumps: An Accelerometry Evaluation.

OBJECTIVES: To explore the effects of wearing compression garments on joint mechanics, soft tissue vibration and muscle activities during drop jumps. METHODS: Twelve healthy male athletes were recruited to execute drop jumps from heights of 30, 45 and 60 cm whilst wearing compression shorts (CS) and control shorts (CON). Sagittal plane kinematics, ground reaction forces, accelerations of the quadriceps femoris (QF), hamstrings (HM) and shoe heel-cup, and electromyography images of the rectus femoris (RF) and biceps femoris (BF) were collected. RESULTS: Compared with wearing CON, wearing CS significantly reduced the QF peak acceleration at 45 and 60 cm and the HM peak acceleration at 30 cm. Wearing CS significantly increased the damping coefficient for QF and HM at 60 cm compared with wearing CON. Moreover, the peak transmissibility when wearing CS was significantly lower than that when wearing CON for all soft tissue compartments and heights, except for QF at 30 cm. Wearing CS reduced the RF activity during the pre-, post-, and eccentric activations for all heights and concentric activations at 45 cm; it also reduced the BF activity during post- and eccentric activations at 30 and 60 cm, respectively. The hip and knee joint moments and power or jump height were unaffected by the garment type. CONCLUSION: Applying external compression can reduce soft tissue vibrations without compromising neuromuscular performance during strenuous physical activities that involve exposure to impact-induced vibrations.

In Vivo Foot and Ankle Kinematics During Activities Measured by Using a Dual Fluoroscopic Imaging System: A Narrative Review.

Foot and ankle joints are complicated anatomical structures that combine the tibiotalar and subtalar joints. They play an extremely important role in walking, running, jumping and other dynamic activities of the human body. The in vivo kinematic analysis of the foot and ankle helps deeply understand the movement characteristics of these structures, as well as identify abnormal joint movements and treat related diseases. However, the technical deficiencies of traditional medical imaging methods limit studies on in vivo foot and ankle biomechanics. During the last decade, the dual fluoroscopic imaging system (DFIS) has enabled the accurate and noninvasive measurements of the dynamic and static activities in the joints of the body. Thus, this method can be utilised to quantify the movement in the single bones of the foot and ankle and analyse different morphological joints and complex bone positions and movement patterns within these organs. Moreover, it has been widely used in the field of image diagnosis and clinical biomechanics evaluation. The integration of existing single DFIS studies has great methodological reference value for future research on the foot and ankle. Therefore, this review evaluated existing studies that applied DFIS to measure the in vivo kinematics of the foot and ankle during various activities in healthy and pathologic populations. The difference between DFIS and traditional biomechanical measurement methods was shown. The advantages and shortcomings of DFIS in practical application were further elucidated, and effective theoretical support and constructive research direction for future studies on the human foot and ankle were provided.

Gender Difference in Architectural and Mechanical Properties of Medial Gastrocnemius-Achilles Tendon Unit In Vivo.

This study aims to explore whether gender differences exist in the architectural and mechanical properties of the medial gastrocnemius-Achilles tendon unit (gMTU) in vivo. Thirty-six healthy male and female adults without training experience and regular exercise habits were recruited. The architectural and mechanical properties of the gMTU were measured via an ultrasonography system and MyotonPRO, respectively. Independent t-tests were utilized to quantify the gender difference in the architectural and mechanical properties of the gMTU. In terms of architectural properties, the medial gastrocnemius (MG)'s pennation angle and thickness were greater in males than in females, whereas no substantial gender difference was observed in the MG's fascicle length; the males possessed Achilles tendons (ATs) with a longer length and a greater cross-sectional area than females. In terms of mechanical properties, the MG's vertical stiffness was lower and the MG's logarithmic decrement was greater in females than in males. Both genders had no remarkable difference in the AT's vertical stiffness and logarithmic decrement. Gender differences of individuals without training experience and regular exercise habits exist in the architectural and mechanical properties of the gMTU in vivo. The MG's force-producing capacities, ankle torque, mechanical efficiency and peak power were higher in males than in females. The load-resisting capacities of AT were greater and the MG strain was lesser in males than in females. These findings suggest that males have better physical fitness, speed and performance in power-based sports events than females from the perspective of morphology and biomechanics.

[Progress on in vivo ankle biomechanics based on dual fluoroscopic imaging technology].

The technical deficiencies in traditional medical imagining methods limit the study of in vivo ankle biomechanics. A dual fluoroscopic imaging system (DFIS) provides accurate and non-invasive measurements of dynamic and static activities in joints of the body. This approach can be used to quantify the movement in the single bones of the ankle and analyse different morphological and complex bone positions and movement patterns within these organs and has been widely used in the field of image diagnosis and evaluation of clinical biomechanics. This paper reviews the applications of DFIS that were used to measure the in vivo kinematics of the ankle in the field of clinical and sports medicine. The advantages and shortcomings of DFIS in the practical application are summarised. We further put forward effective research programs for understanding the movement as well as injury mechanism of the ankle in vivo, and provide constructive research direction for future study.

Systematic Review of the Impact of Transcranial Direct Current Stimulation on the Neuromechanical Management of Foot and Ankle Physical Performance in Healthy Adults.

Objective: This study aims to review existing literature regarding the effects of transcranial direct current stimulation (tDCS) on the physical performances of the foot and ankle of healthy adults and discuss the underlying neurophysiological mechanism through which cortical activities influence the neuromechanical management of the physical performances of the foot and ankle. Methods: This systematic review has followed the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses. A systematic search was performed on PubMed, EBSCO, and Web of Science. Studies were included according to the Participants, Intervention, Comparison, Outcomes, and Setting inclusion strategy. The risk of bias was assessed through the Cochrane Collaboration tool, and the quality of each study was evaluated through the Physiotherapy Evidence Database (PEDro) scale. Results: The electronic search resulted in 145 studies. Only eight studies were included after screening. The studies performed well in terms of allocation, blinding effectiveness, and selective reporting. Besides, the PEDro scores of all the studies were over six, which indicated that the included studies have high quality. Seven studies reported that tDCS induced remarkable improvements in the physical performances of the foot and ankle, including foot sole vibratory and tactile threshold, toe pinch force, ankle choice reaction time, accuracy index of ankle tracking, and ankle range of motion, compared with sham. Conclusion: The results in these studies demonstrate that tDCS is promising to help improve the physical performances of the foot and ankle. The possible underlying mechanisms are that tDCS can ultimately influence the neural circuitry responsible for the neuromechanical regulation of the foot and ankle and then improve their physical performances. However, the number of studies included was limited and their sample sizes were small; therefore, more researches are highly needed to confirm the findings of the current studies and explore the underlying neuromechanical effects of tDCS.