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Muscle stiffness estimated using shear wave elastography can provide an index of individual muscle force during isometric contraction and may therefore be a promising method for quantifying co-contraction. We estimated the shear modulus of the lateral gastrocnemius (LG) muscle using supersonic shear wave imaging and measured its myoelectrical activity using surface electromyography (sEMG) during graded isometric contractions of plantar flexion and dorsiflexion (n=7). During dorsiflexion, the average shear modulus was 26±6kPa at peak sEMG amplitude, which was significantly less (P=0.02) than that measured at the same sEMG level during plantar flexion (42±10kPa). The passive tension during contraction was estimated using the passive LG muscle shear modulus during a passive ankle rotation measured at an equivalent ankle angle to that measured during contraction. The passive shear modulus increased significantly (P<0.01) from the plantar flexed position (16±5kPa) to the dorsiflexed position (26±9kPa). Once this change in passive tension from joint rotation was accounted for, the average LG muscle shear modulus due to active contraction was significantly greater (P<0.01) during plantar flexion (26±8kPa) than at sEMG-matched levels of dorsiflexion (0±4kPa). The negligible shear modulus estimated during isometric dorsiflexion indicates negligible active force contribution by the LG muscle, despite measured sEMG activity of 19% of maximal voluntary plantar flexion contraction. This strongly suggests that the sEMG activity recorded from the LG muscle during isometric dorsiflexion was primarily due to cross-talk. However, it is clear that passive muscle tension changes can contribute to joint torque during isometric dorsiflexion.

Exercise-induced fatigue causes changes within the central nervous system that decrease force production capacity in fatigued muscles. The impact on unrelated, non-exercised muscle performance is still unclear. The primary aim of this study was to examine the impact of a bilateral forearm muscle contraction on the motor function of the distal and unrelated ankle plantar-flexor muscles. The secondary aim was to compare the impact of maximal and submaximal forearm contractions on the non-fatigued ankle plantar-flexor muscles. Maximal voluntary contractions (MVC) of the forearm and ankle plantar-flexor muscles as well as voluntary activation (VA) and twitch torque of the ankle plantar-flexor muscles were assessed pre-fatigue and throughout a 10-min recovery period. Maximal (100 % MVC) and submaximal (30 % MVC) sustained isometric handgrip contractions caused a decreased handgrip MVC (to 49.3 ± 15.4 and 45.4 ± 11.4 % of the initial MVC for maximal and submaximal contraction, respectively) that remained throughout the 10-min recovery period. The fatigue protocols also caused a decreased ankle plantar-flexor MVC (to 77 ± 8.3 and 92.4 ± 6.2 % of pre-fatigue MVC for maximal and submaximal contraction, respectively) and VA (to 84.3 ± 15.7 and 97.7 ± 16.1 % of pre-fatigue VA for maximal and submaximal contraction, respectively). These results suggest central fatigue created by the fatiguing handgrip contraction translated to the performance of the non-exercised ankle muscles. Our results also show that the maximal fatigue protocol affected ankle plantar-flexor MVC and VA more severely than the submaximal protocol, highlighting the task-specificity of neuromuscular fatigue.

Limited ankle dorsiflexion range of motion is one of the most important risk factors for lower limb injury, which changes the biomechanics and the neuromuscular control of the lower limb muscles. This study aims to test the effectiveness of a comprehensive corrective exercise program (CCEP) on the range of motion, proprioception, dynamic balance, and muscle activation in female athletes with limited weight-bearing lunge ankle dorsiflexion range of motion. 30 female athletes aged 15 to 25 years with dorsiflexion under 34° were randomized to two groups. The intervention group (n = 15) received eight weeks of CCEP including soft tissue mobilization, joint mobilization, stretching, and strengthening, and the control (n = 15) group did not receive any intervention. range of motion, proprioception, dynamic balance, and muscle activation were assessed before and after the intervention. The training group showed clinically acceptable and statistically significant changes in ankle dorsiflexion range of motion (ES = 0.714), balance (ES = 0.423), and proprioception (ES = 0.253; P < 0.05). There were significant changes in the activity of the tibialis anterior and soleus muscles in the dynamic overhead squat test (descending and ascending phases) and the activity of the medial gastrocnemius in the descending phase decreased significantly (P < 0.05). No significant change was observed in the activity of the peroneus longus muscle (P > 0.05). The findings show that CCEP appears to be beneficial in increasing dorsiflexion range of motion, proprioception, balance, and decreasing ankle muscle activity among individuals with limited ankle dorsiflexion. Improving the dorsiflexion range of motion may be promising for reducing ankle sprain injury.

Deficits in the propioceptive system of the ankle contribute to chronic ankle instability (CAI). Recently, whole-body-vibration (WBV) training has been introduced as a preventive and rehabilitative tool.   To evaluate how a 6-week WBV training program on an unstable surface affected balance and body composition in recreational athletes with CAI.   Randomized controlled clinical trial.   Research laboratory.   Fifty recreational athletes with self-reported CAI were randomly assigned to a vibration (VIB), nonvibration (NVIB), or control group.   The VIB and NVIB groups performed unilateral balance training on a BOSU 3 times weekly for 6 weeks. The VIB group trained on a vibration platform, and the NVIB group trained on the floor.   We assessed balance using the Biodex Balance System and the Star Excursion Balance Test (SEBT). Body composition was measured by dual-energy x-ray absorptiometry.   After 6 weeks of training, improvements on the Biodex Balance System occurred only on the Overall Stability Index ( P = .01) and Anterior-Posterior Stability Index ( P = .03) in the VIB group. We observed better performance in the medial ( P = .008) and posterolateral ( P = .04) directions and composite score of the SEBT in the VIB group ( P = .01) and in the medial ( P < .001), posteromedial ( P = .002), and posterolateral ( P = .03) directions and composite score of the SEBT in the NVIB group ( P < .001). No changes in body composition were found for any of the groups.   Only the VIB group showed improvements on the Biodex Balance System, whereas the VIB and NVIB groups displayed better performance on the SEBT.

AimPrevious stretching studies mostly investigated effects on the skeletal muscle but comprehensive explorations regarding the role of the connective tissue are scarce. Since the deep fascia has been demonstrated to be sensitive to mechanical tension, it was hypothesized that the fascia would also respond to stretching, contributing to enhanced range of motion (ROM).MethodsForty (40) recreationally active participants (male: n = 25, female: n = 15) were included in the randomized controlled cross-over trial and allocated to different groups performing 5 min static (STAT) or dynamic (DYN) plantar flexor stretching or control condition (CC) in a random order. Pre- and immediately post-intervention, muscle and fascia stiffness, as well as muscle and fascia thickness were measured using high-resolution ultrasound and strain elastography. ROM was assessed in the ankle joint via the knee to wall test (KtW) and goniometer.ResultsSTAT reduced both, muscle and fascia stiffness (d = 0.78 and 0.42, p < 0.001, respectively), while DYN did not reduce stiffness compared to the control condition (p = 0.11–0.41). While both conditions showed significant increases in the KtW (d = 0.43–0.46, p = 0.02–0.04), no significant differences to the CC were observed for the isolated ROM testing (p = 0.09 and 0.77). There was a small correlation between fascia stiffness decreases and ROM increases (r = − 0.25, p = 0.006) but no association was found between muscle stiffness decreases and ROM increases (p = 0.13–0.40).ConclusionOur study is the first to reveal stretch-induced changes in fascia stiffness. Changes of fascia`s but not muscle`s mechanical properties may contribute to increased ROM following stretching.

Robot-assisted training is a promising tool under development for improving walking function based on repetitive goal-oriented task practice. The challenges in developing the controllers for gait training devices that promote desired changes in gait is complicated by the limited understanding of the human response to robotic input. A possible method of controller formulation can be based on the principle of bio-inspiration, where a robot is controlled to apply the change in joint moment applied by human subjects when they achieve a gait feature of interest. However, it is currently unclear how lower extremity joint moments are modulated by even basic gait spatio-temporal parameters. In this study, we investigated how sagittal plane joint moments are affected by a factorial modulation of two important gait parameters: gait speed and stride length. We present the findings obtained from 20 healthy control subjects walking at various treadmill-imposed speeds and instructed to modulate stride length utilizing real-time visual feedback. Implementing a continuum analysis of inverse-dynamics derived joint moment profiles, we extracted the effects of gait speed and stride length on joint moment throughout the gait cycle. Moreover, we utilized a torque pulse approximation analysis to determine the timing and amplitude of torque pulses that approximate the difference in joint moment profiles between stride length conditions, at all gait speed conditions. Our results show that gait speed has a significant effect on the moment profiles in all joints considered, while stride length has more localized effects, with the main effect observed on the knee moment during stance, and smaller effects observed for the hip joint moment during swing and ankle moment during the loading response. Moreover, our study demonstrated that trailing limb angle, a parameter of interest in programs targeting propulsion at push-off, was significantly correlated with stride length. As such, our study has generated assistance strategies based on pulses of torque suitable for implementation via a wearable exoskeleton with the objective of modulating stride length, and other correlated variables such as trailing limb angle.

When fitting prosthetic feet, prosthetists fuse information from their visual assessment of patient gait with the patient’s communicated perceptions and preferences. In this study, we sought to simultaneously and independently assess patient and prosthetist preference for prosthetic foot stiffness using a custom variable-stiffness prosthesis. In the first part of the experiment, seven subjects with below-knee amputation walked on the variable-stiffness prosthetic foot set to a randomized stiffness, while several prosthetist subjects simultaneously observed their gait. After each trial, the amputee subjects and prosthetist subjects indicated the change to stiffness that they would prefer (increase or decrease). This paradigm allowed us to simultaneously measure amputee subject and prosthetist subject preferences, and provided a reliability index indicating the consistency of their preferences. In the second part of the experiment, amputee subjects were instructed to communicate verbally with one prosthetist subject to arrive at a mutually preferred stiffness. On average, prosthetist subjects preferred a 26% higher stiffness than amputee subjects ( p  < 0.001), though this depended on the amputee subject ( p  < 0.001). Prosthetist subjects were also considerably less consistent than amputee subjects in their preferences (CV of 5.6% for amputee subjects, CV of 23% for prosthetist subjects; p  = 0.014). Mutual preference seemed to be dictated by the specific patient-prosthetist dynamic, and no clear trends emerged.

Exposure footwear for firemen (EFF) is a crucial component of firefighters’ personal protective equipment, designed to protect against hazards, such as heat, punctures, impact, and electrocution. However, its effect on gait biomechanics remains unclear. This study was aimed to investigate the influence of EFF on firefighters’ lower limb biomechanical performance and the underlying mechanisms. Twenty healthy male firefighters (mean height: 175.41 ± 4.39 cm, mean weight: 65.74 ± 5.81 kg, mean BMI: 21.37 ± 2.17 kg/m 2 ) were randomly assigned to wear EFF and fitness training shoes for comparison during walking tasks. Lower limb biomechanics were analyzed, focusing on joint range of motion (ROM), moments, work and muscle activity. The results indicated that wearing EFF led to increased hip and knee joint ROM in the sagittal plane, reduced ankle and metatarsophalangeal (MTP) joint ROM in the sagittal plane, increased peak hip flexion/extension and ankle dorsiflexion moments, and decreased MTP joint dorsiflexion peak moments. EFF use also resulted in increased positive work done by the hips, increased negative work done by the ankles, reduced positive work done by the ankle joints, and increased negative work by the MTP joint, The activation levels of the rectus femoris and tibialis anterior muscles were higher when wearing EFF compared to fitness training shoes. In conclusion, EFF significantly alters the biomechanical characteristics of firefighters’ lower limbs during walking, leading to elevated muscle activation in the rectus femoris and tibialis anterior. This increased demand on the lower limb muscle groups for mechanical energy generation heightens the risk of fatigue, musculoskeletal injuries, and osteoarthritis. Therefore, it is recommended that EFF boots be designed using lightweight and flexible materials. Additionally, training programs should prioritize strengthening the hip flexor/extensor, ankle dorsiflexor muscle groups, and especially the rectus femoris and tibialis anterior muscles.

We aimed to investigate the effects of ankle taping on lower extremity biomechanics related to injury development and how these effects change after sports-specific use. Randomized, repeated measures design with three conditions: Barefoot, tape applied fresh, and tape after sports-specific use (between-subject factor: sex). Twenty-five healthy participants (ten female) performed sports-specific movements, including running, drop jumping, and 180° change of direction, under the three conditions. Kinetic and kinematic data were collected using 3D motion capturing and force platforms. Tape applied fresh and tape after sports-specific use significantly reduced peak ankle inversion. Biomechanical risk factors for anterior cruciate ligament or running overuse injuries were either unchanged or decreased with tape applied fresh, except for the peak loading rate of the resultant ground reaction force, which increased between 4% and 18% between movement types. After 15 minutes of sports-specific use of the tape, the alterations induced by tape applied fresh remained for some biomechanical risk factors while they became closer to barefoot again for others, indicating a differential response to prolonged use of taping for different biomechanical variables. Ankle taping protects the ankle joint by reducing biomechanical risk factors associated with ankle sprains, and most biomechanical risk factors for anterior cruciate ligament or running overuse injuries are not increased. Further research is needed to explore the duration of protective effects, variations across sports, and its impact on patients with chronic ankle instability, contributing to a more comprehensive understanding of ankle taping's influence on lower extremity biomechanics.

The prevention and management of injuries in runners is a key area of research in sports medicine. Fatigue during running can lead to biomechanical imbalances and inhibition of stabilizing muscles, increasing the risk of injury. With the ankle being the most commonly injured joint in runners, rigid tape (RT) and Kinesiotape (KT) have been proposed as effective methods to improve joint stability and reduce injury risk. The objective of this study was to compare the effects of a KT and RT and no tape (control group) on lower limb balance, ankle dorsiflexion ROM, and electromyographic (EMG) activation of the pronator and supinator muscles of the ankle during a Single Leg Drop Jump (SLDJ) following a treadmill fatigue protocol. From March 1 st until April 10 th , 2024, a cross-over clinical trial with three conditions: control group, with a RT, and with KT was conducted with n = 22 well-trained runners aged 29.29 ±  10.98 years. Lower limb stability, ankle dorsiflexion mobility, SLDJ parameters, and electromyographic activation of the ankle muscles (tibialis anterior (TA), extensor digitorum longus (EDL), peroneus longus (PL), and medial gastrocnemius (MG)) during a SLDJ were analyzed Pre and Post fatigue protocol, involving a 30-minute run at 85% of the maximal aerobic speed on a treadmill. Statistical analysis was conducted using repeated-measures ANOVA with Bonferroni correction. The RT bandage decreased ankle dorsiflexion ROM compared to both KT bandage and a control group during pre fatigue treadmill protocol measurements in the lunge and Y Balance Tests (specifically in the anterior direction). Group-by-time interaction showed significant differences for the lunge test (p =  0.045), SLDJ height (p =  0.014), flight time (p =  0.019) and ground contact time (p =  0.035). With the RT condition, the runners exhibited higher peak activation of the EDL muscle compared to the KT and control group during initial landing (p =  0.028), with a lesser decay in activation during take-off (p =  0.016). The KT showed a significant increase in the activation of the PL muscle during the first contact phase of the SLDJ (p =  0.046). Concerning flight and contact time during the SLDJ, both KT and RT proved beneficial in mitigating fatigue symptoms before and after the treadmill protocol. Regarding the RT bandage’s specific effects on muscle activation, our findings indicate that the RT group exhibited higher peak activation of the EDL muscle compared to the KT and control groups during initial landing, with a lesser decay in activation during take-off. The KT showed a significant increase in the activation of the PL muscle during the first contact phase of the SLDJ. To conclude, our study highlights the potential benefits of both KT and RT in reducing fatigue symptoms during SLDJ. The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12624000099527) on February 2 nd , 2024 ( https://anzctr.org.au/ ).