Medial Gastrocnemius Activity Research Articles

Knee position affects medial gastrocnemius and soleus activation during dynamic plantarflexion: no evidence for an inter-muscle compensation in healthy young adults.

Knee joint position influences ankle torque, but it is unclear whether the soleus compensates to counteract the reductions in gastrocnemius output during knee-flexed versus knee-extended plantarflexions. Therefore, the purpose of this study was to determine the effects of knee joint position and plantarflexion contraction velocity on ankle plantarflexion torque and electromyography activity of the medial gastrocnemius and soleus in healthy young adults. Healthy male participants (n=30) performed concentric plantar flexions in a custom-built dynamometer from 15° dorsiflexion to 30° plantarflexion at gradually increasing velocities during each contraction at 30, 60, 120, 180, and 210°s-1 in a supine position with the knee fully extended and while kneeling with the knee fixed in 90° flexion. Two 16-channel linear electromyographic (EMG) arrays were placed over the medial gastrocnemius and soleus muscles. Plantarflexion torque during flexed-knee versus extended-knee plantarflexions was 31% lower (P=0.002) averaged across the five contraction velocities. The overall EMG activity of the medial gastrocnemius was 35% lower (P=0.002) during knee-flexed versus knee-extended plantarflexions. In the first half of plantarflexions at slower contractions, soleus EMG activity was 15% and 28% higher (both P=0.002) in knee-flexed versus knee-extended plantarflexion, respectively. We conclude that knee position affects medial gastrocnemius and soleus activation during dynamic plantarflexion, with plantarflexion torque being smaller in the knee-flexed versus knee-extended position. However, we found no evidence that changes in soleus activation would compensate for the decrease in medial gastrocnemius activation.

Effect of Foot Position on Ankle Muscle Activity During Wobble Board Training in Individuals With Chronic Ankle Instability

ObjectiveThe purpose of this study was to compare the effects of foot positioning on muscle activities of the peroneus longus (PL), medial gastrocnemius (MG), and tibialis anterior (TA)/PL ratio in individuals with chronic ankle instabilities (CAI) during wobble board training. MethodsThirty individuals with CAI were included, and statistical significance of PL and MG muscle activities was determined using 1-way repeated measures analysis of variance alongside TA/PL activity ratio at the university research laboratory. The participants performed the wobble board training in 3 different foot positions: medial from the centerline of the wobble board (WBT-M), middle from the centerline of the wobble board, and lateral from the centerline of the wobble board (WBT-L). Peroneus longus, MG, and TA muscle activities were measured using surface electromyography. ResultsPeroneus longus activity was significantly higher in the WBT-L position than in the other 2 positions, and it was significantly higher in the middle from the centerline of the wobble board than in the WBT-M position. Medial gastrocnemius activity was significantly greater in the WBT-L position than in the other 2 positions. Tibialis anterior/PL ratio was higher in the WBT-M position than in the other 2 positions. ConclusionThe findings of this study showed that WBT-L increased PL muscle activity by >70% of the maximal voluntary isometric contraction without increasing TA/PL ratio in individuals with CAI.

Comparison of Muscular Activity During Running with New and Used Military Boots and Running Footwears in Healthy Individuals: A Clinical Trial Study

Background: The type of footwear worn by military personnel and others could increase the risk of overuse injuries. Objectives: This study aimed to compare muscular activity during running with new and used military boots and running footwear in healthy individuals. Methods: Thirty healthy males were given a new pair of running footwear (n = 15) and thermoplastic polyurethane military boots (n = 15). Participants in each group were asked to wear these shoes for 6 months. Electromyographic activity of the dominant limb muscles was recorded during running at a speed of 3.3 m/s before and after 6 months. Results: The results indicated significant differences in muscle activity based on the type of footwear worn during various phases of running. Specifically, muscles such as the tibialis anterior, vastus lateralis, rectus femoris, biceps femoris, and semitendinosus showed varied activity during phases such as loading, mid-stance, and push-off. Additionally, there were significant effects of time on certain muscles, including the tibialis anterior and gastrocnemius medialis during the push-off phase. Interactions between footwear type and time were observed for the semitendinosus and gluteus medius during the loading phase, and the gastrocnemius medialis during the push-off phase. Conclusions: The results of this study indicate a decrease in muscle activity for most lower limb muscles in the military boots group compared to the running footwear group during the stance phase of running. The magnitude of gastrocnemius medialis activity increased in the military boots group (but not in the running footwear group) from pre-test to post-test during the push-off phase.

Relation between stretch and activation of the medial gastrocnemius muscle during gait in children with cerebral palsy compared to typically developing children

Stretch hyperreflexia is often a target for treatment to improve gait in children with spastic cerebral palsy (CP). However, the presence of stretch hyperreflexia during gait remains debated. Therefore, we assessed the relation between gastrocnemius medialis muscle-tendon stretch and muscle activation during gait in children with CP compared to typically developing (TD) children. 3D gait analysis including electromyography (EMG) and dynamic ultrasound was carried out to assess, respectively gastrocnemius medialis activation and fascicle, belly, and tendon stretch during treadmill walking. Musculotendon-unit stretch was also estimated using OpenSim. Ratios of EMG/peak lengthening velocities and accelerations were compared between CP and TD. Velocity and acceleration peaks prior to EMG peaks were qualitatively assessed. EMG/velocity and EMG/acceleration ratios were up to 500% higher for CP (n = 14) than TD (n = 15) for most structures. Increased late swing muscle activation in CP was often preceded by fascicle and musculotendon-unit peak lengthening velocity, and early stance muscle activation by peaks in multiple structures. Increased muscle activation in CP is associated with muscle-tendon stretch during gait. Concluding, late swing muscle activation in CP appears velocity-dependent, whereas early stance activation can be velocity- and acceleration-dependent. These insights into stretch reflex mechanisms during gait can assist development of targeted interventions.

Effects of textured insoles on dynamic balance and ankle muscle activity in soccer players with and without chronic ankle instability.

Chronic ankle instability (CAI) poses challenges in sports. Textured insoles (TI) are a promising intervention for enhancing dynamic balance in CAI athletes. This study aimed to investigate the effects of TI on dynamic balance performance and ankle muscle activity in soccer players with and without CAI. Thirty-eight soccer players (19 CAI, 19 non-CAI) participated. Participants performed a modified star excursion balance test (mSEBT) while wearing TI and standard insoles (SI). The %SEBT reach distance and electromyography (EMG) activity of tibialis anterior (TA), medial gastrocnemius (MG), and peroneus longus (PL) were measured during maximum reached in each direction of the mSEBT. No significant effects or interactions were found between ankle conditions (CAI vs. non-CAI) or insole types (TI vs. SI) on %SEBT reach. However, CAI players showed greater MG activity in posteromedial and posterolateral direction (P=0.04, P=0.01). Overall, the application of TI did not have immediate effects on dynamic balance performance or ankle muscle activity in either CAI or non-CAI soccer players. Nonetheless, CAI players seemed to employ a different ankle strategy involving the MG muscle, possibly to control stability during dynamic movement, particularly in the posteromedial and posterolateral directions.

EMG coherence of foot and ankle muscles increases with a postural challenge in men

BackgroundThe functional role of intrinsic foot muscles in the control of standing balance is often overlooked in rehabilitation, partly because the interactions with ankle muscles are poorly understood. Research questionHow does coactivation of Flexor Digitorum Brevis (FDB) and soleus (SOL) vary across standing tasks of increasing difficulty. MethodsPostural sway (Centre of Pressure, CoP) and the electromyographic (EMG) activity of FDB, SOL, Medial Gastrocnemius (MG) and Tibialis Anterior (TA) were measured during bipedal standing, tandem stance, one-legged balance, and standing on toes. Coherence of the rectified EMG signals for SOL and FDB in two bandwidths (0–5 and 10–20 Hz) was calculated as a coactivation index. Results and significanceThe CoP sway and the EMG activity of all muscles was greater (P<0.05) for the three difficult tasks. Significant coherence between the SOL and FDB EMG activity was found in both frequency regions: 0–5 and 10–20 Hz. The coherence integral increased with the difficulty of the postural task, especially in the 10–20 Hz band. The findings underscore the important role of FDB in the control of standing balance across tasks and its coactivation with SOL. Clinical recommendations to improve balance control need to consider the interaction between the plantar flexor and intrinsic-foot muscles.

Antagonist Activation Measurement in Triceps Surae Using High-Density and Bipolar Surface EMG in Chronic Hemiparesis.

After a stroke, antagonist muscle activation during agonist command impedes movement. This study compared measurements of antagonist muscle activation using surface bipolar EMG in the gastrocnemius medialis (GM) and high-density (HD) EMG in the GM and soleus (SO) during isometric submaximal and maximal dorsiflexion efforts, with knee flexed and extended, in 12 subjects with chronic hemiparesis. The coefficients of antagonist activation (CAN) of GM and SO were calculated according to the ratio of the RMS amplitude during dorsiflexion effort to the maximal agonist effort for the same muscle. Bipolar CAN (BipCAN) was compared to CAN from channel-specific (CsCAN) and overall (OvCAN) normalizations of HD-EMG. The location of the CAN centroid was explored in GM, and CAN was compared between the medial and lateral portions of SO. Between-EMG system differences in GM were observed in maximal efforts only, between BipCAN and CsCAN with lower values in BipCAN (p < 0.001), and between BipCAN and OvCAN with lower values in OvCAN (p < 0.05). The CAN centroid is located mid-height and medially in GM, while the CAN was similar in medial and lateral SO. In chronic hemiparesis, the estimates of GM hyperactivity differ between bipolar and HD-EMGs, with channel-specific and overall normalizations yielding, respectively, higher and lower CAN values than bipolar EMG. HD-EMG would be the way to develop personalized rehabilitation programs based on individual antagonist activations.

Usability of the novel ankle training equipment with spring resistance-based plantar press exercises in the standing position: A focus on chronic stroke patients with hemiplegic gait.

To improve gait disability in patients with chronic stroke, ankle muscle strengthening and calf muscle stretching exercises are required. However, currently available ankle training equipment limit ankle exercises based on the position. Recently developed ankle training equipment enables spring resistance-based plantar press exercises to be performed in the standing position with weight support. To conduct a usability test of the ankle training equipment in the standing position by stroke patients with hemiplegic gait and verify its effects on ankle movements. The ankle training equipment was applied to five patients with chronic stroke and hemiplegic gait. In the standing position, the patients performed forefoot and rearfoot press exercises in the affected side with a day's interval at 20 repetitions maximum (RM). During the exercises, surface electromyography (sEMG) was used to measure the maximum voluntary isometric contraction (%MVIC) of the leg muscles. The System Usability Scale (SUS) was used to assess the ankle training equipment. Wilcoxon signed-rank test was used to evaluate the differences in muscle activity between the two exercises. Forefoot and rearfoot press exercises increased the %MVIC in the biceps femoris. Additionally, the tibialis anterior and medial gastrocnemius activity was significantly different between the two exercises. The SUS was 78.75% (SD 12.7). The usability test of the passive-control foot press trainer (PFPT) that with improvements in the structure and functions for convenience, it could be commercialized. PFPT could be an alternative to the ankle rehabilitation robot that necessitates a sitting position.

Effect of Six Months of Using Thermoplastic Polyurethane and Rubber Military Boots on Lower Limb Muscle Activities During Running

Background: The age of boots is a significant factor that can impact the risk of injury during daily activities. Conversely, military personnel rely on their footwear to meet the physical demands of their daily professional tasks. Objectives: This study aimed to evaluate how wearing thermoplastic polyurethane (TPU) and rubber military boots for six months affects lower limb muscle activity during running. Methods: Thirty healthy male participants were provided with two new pairs of rubber and TPU military boots and instructed to wear them for six months. Electromyography signals were recorded during a pre-test and after six months while the participants ran at a speed of 3.2 m/s. Statistical analysis was conducted using a two-way ANOVA with repeated measures, with a significance level of 0.05. Results: The results did not show a significant overall effect of "boots" or "time" on muscle activities during running. However, there were significant boot-by-time interactions for muscle activities during different phases of the running cycle. These interactions were observed for the tibialis anterior (P = 0.037, η2p = 0.146), gastrocnemius medialis (P = 0.023, η2p = 0.172), and gluteus medius (P = 0.038, η2p = 0.144) activities during the loading phase, tibialis anterior activity at the mid-stance phase (P = 0.003, η2p = 0.278), and gastrocnemius medialis activity during the push-off phase (P = 0.046, η2p = 0.135). Conclusions: Wearing military boots appears to affect muscle activities, particularly the tibialis anterior, in healthy males. These findings underscore the importance of careful boot selection for running activities. Understanding the reasons behind differences in muscle activity between TPU and rubber military boots can inform further research and the development of specialized footwear tailored to specific operational needs.

Quantifying Plantar Flexor Muscles Stiffness During Passive and Active Force Generation Using Shear Wave Elastography in Individuals With Chronic Stroke

ObjectivesThis study aims to investigate the mechanical properties of paretic and healthy plantar flexor muscles and assesses the spatial distribution of stiffness between the gastrocnemius medialis (GM) and lateralis (GL) during active force generation. MethodsShear wave elastography measurements were conducted on a control group (CNT, n=14; age= 59.9 ± 10.6 years; BMI= 24.5 ± 2.5 kg/m2) and a stroke survivor group (SSG, n = 14; age = 63.2 ± 9.6 years; BMI = 23.2 ± 2.8 kg/m2). Shear modulus within the GM and GL was obtained during passive ankle mobilization at various angles of dorsiflexion (P0= 0°; P1= 10°; P2= 20°; P3= -20° and P4= -30°) and during different levels of maximal voluntary contraction (MVC) (100%, 30%, 50%, 70%). Muscle activation of GM, GL, and tibialis anterior was also evaluated. ResultsThe results revealed a significant increase in passive stiffness within the paretic plantar flexor muscles under high tension during passive mobilization (p<0.05). Yet, during submaximal and maximal MVC, the paretic plantar flexors exhibited decreased active stiffness levels (p<0.05). A notable discrepancy was found between the stiffness of the GM and GL muscles, with the GM demonstrating greater stiffness from 0° of dorsiflexion in the SSG (p<0.05), and from 10° of dorsiflexion in the CNT (p<0.05). No significant difference in stiffness was observed between the GM and GL muscles during active conditions. ConclusionStroke affects the mechanical properties differently depending on the state of muscle activation. Notably, the distribution of stiffness among synergistic plantar flexor muscles varied in passive condition, while remaining consistent in active condition.

Relationship between Trailing Limb Angle and Medial Gastrocnemius Muscle Activity at Different Walking Speeds

Relationship between Trailing Limb Angle and Medial Gastrocnemius Muscle Activity at Different Walking Speeds

Muscle activation while running on the ground compared to artificial turf in males with pronated and supinated feet

BackgroundRunning on different surfaces, including natural and artificial surfaces, requires different gait mechanics, especially in individuals with foot deformity. Research questionHow muscle activity change during running on the ground and artificial turf in males with pronated and supinated feet? MethodsIn this quasi-experimental study, we assessed a cohort of young male subjects, classified as healthy (n = 10), and with pronated (n = 10) or supinated (n = 10) feet. An electromyographic system was used to record lower limb muscle activity while running on the ground and artificial turf at constant speed (3.2 m/s). ResultsResults demonstrated significant main effects of the "surface" factor for vastus medialis activity during the loading phase (p = 0.040, η2 =0.147). Paired comparison revealed significantly greater vastus medialis activity while running on artificial grass with respect to the ground. A significant effect of the “group” factor was found for medial gastrocnemius during loading phase (p = 0.020, η2 =0.250). Paired-wise comparison revealed significantly lower medial gastrocnemius activity in the pronated and supinated feet groups than in the healthy group. SignificanceThe healthy group may possess better neuromuscular control, allowing them to effectively coordinate the activation of the medial gastrocnemius with other muscles involved in running. Based on these findings, running on artificial turf is useful when the runner would like to strengthen vastus medialis muscle. The runner should carefully choose the running surface according to his/her state and training session goal.

Comparison of biomechanical analysis results using different musculoskeletal models for children with cerebral palsy.

Introduction: Musculoskeletal model-based simulations have gained popularity as a tool for analyzing human movement biomechanics. However, when examining the same gait, different models with varying anatomical data and assumptions may produce inconsistent biomechanical results. This inconsistency is particularly relevant for children with cerebral palsy, who often exhibit multiple pathological gait patterns that can impact model outputs. Methods: The aim of this study was to investigate the effect of selecting musculoskeletal models on the biomechanical analysis results in children with cerebral palsy. Gait data were collected from multiple participants at slow, medium, and fast velocities. Joint kinematics, joint dynamics, and muscle activation were calculated using six popular musculoskeletal models within a biomechanical simulation environment. Results: The degree of inconsistency, measured as the root-mean-square deviation, in kinematic and kinetic results produced by the different models ranged from 4% to 40% joint motion range and 0%-28% joint moment range, respectively. The correlation between the results of the different models (both kinematic and kinetic) was good (R0.85, P 0.01), with a stronger correlation observed in the kinetic results. Four of the six models showed a positive correlation between the simulated muscle activation of rectus femoris and the surface EMG, while all models exhibited a positive correlation between the activation of medial gastrocnemius and the surface EMG (P 0.01). Discussion: These results provide insights into the consistency of model results, factors influencing consistency, characteristics of each model's outputs, mechanisms underlying these characteristics, and feasible applications for each model. By elucidating the impact of model selection on biomechanical analysis outcomes, this study advances the field's understanding of musculoskeletal modeling and its implications for clinical gait analysis model decision-making in children with cerebral palsy.

Influences of dynamic load phase shifts on the energetics and biomechanics of humans.

Using load-suspended backpacks to reduce vertical peak dynamic load exerted on humans can reduce metabolic costs. However, is it possible to further reduce metabolic cost by modulating dynamic load phase shift? If so, is anti-phase better than the others? In this study, we investigated the biomechanics, energetics and trunk response under phase shifts. Nine subjects wearing an active backpack with 19.4 kg loads walked on a treadmill at 5 km h-1 with four phase shift trials (T1-T4) and a load-locked trial (LK). Our results show that anti-phase trial (T3) assists ankle more and reduces the moment and gastrocnemius medialis activity, while T4 assists knee more and reduces the moment and rectus femoris activity. Due to the load injecting more mechanical energy into human in T3 and T4, the positive centre-of-mass work is significantly reduced. However, the gross metabolic rate is lowest in T4 and 4.43% lower than in T2, which may be because the activations of erector spinae and gluteus maximus are reduced in T4. In addition, T3 increases trunk extensor effort, which may weaken the metabolic advantage. This study provides guidance for improving assistance strategies and human-load interfaces and deepens the understanding of the energetics and biomechanics of human loaded walking.

Muscle coordination patterns in regulation of medial gastrocnemius activation during walking

The ankle plantar flexion in the late stance phase is referred to as the ankle push-off. When the ankle push-off force is enhanced, compensatory adjustments occur in the adjacent phases. The muscle control that achieves these compensatory movements remains unknown, although they are expected to be coordinately regulated across multiple muscles and phases. Muscle synergy is used as a quantification technique for muscle coordination, and this analysis enables the comparison of synchronized activity between multiple muscles. Therefore, this study aimed to elucidate the tuning of muscle synergies in muscle activation adjustment of push-off. It is hypothesized that muscle activation adjustment of push-off is performed in the muscle synergy related to ankle push-off and in the muscle synergy that activates during the adjacent push-off phase. Eleven healthy men participated, and participants manipulated the activity of the medial gastrocnemius during walking through visual feedback. Two conditions were compared as experimental conditions: increasing the muscle activity to 1.6 times that during normal walking (High) and matching it with that during normal walking (Normal). Twelve muscle activities in the trunk and lower limb and kinematic data were recorded. Muscle synergies were extracted by the non-negative matrix factorization. No significant difference was observed in the number of synergies (High: 3.5 ± 0.8, Normal: 3.7 ± 0.9, p = 0.21) and muscle synergy activation timing and duration between the High and Normal conditions (p > 0.27). However, significant differences were observed in the peak muscle activity during the late stance phase of the rectus femoris (RF), biceps femoris (BF) between conditions (RF at High: 0.32 ± 0.21, RF at Normal: 0.45 ± 0.17, p = 0.02; BF at High: 0.16 ± 0.01, BF at Normal: 0.08 ± 0.06 p = 0.02). Although the quantification of force exertion has not been conducted, the modulation of RF and BF activation could have occurred due to the attempts to help knee flexion. Muscle synergies during normal walking are therefore maintained, and slight adjustments in the amplitude of muscle activity occurred for each muscle.

Functional effects of arthroscopic modified Broström procedure on lateral ankle instability: A pilot study

BackgroundThis study aims to assess the mechanical and functional effects of the arthroscopic modified Broström procedure (AMBP) on patients with lateral ankle instability. MethodsEight patients with unilateral ankle instability treated with AMBP and eight healthy subjects were recruited. Healthy subjects, preoperative and one-year postoperative patients were assessed using outcome scales and the Star Excursion Balance Test (SEBT) for dynamic postural control. One-dimensional statistical parametric mapping was performed to compare ankle angle and muscle activation curve during stair descent. ResultsThe patients with lateral ankle instability showed good clinical outcomes and increased posterior lateral reach during the SEBT after the AMBP (p = 0.046). The medial gastrocnemius activation after initial contact was reduced (p = 0.049), and the peroneal longus activation after initial contact was promoted (p = 0.014). ConclusionThe AMBP has functional effects of promoting dynamic postural control and peroneal longus activation within one year of follow-up, which can benefit patients with functional ankle instability. However, the medial gastrocnemius activation was unexpectedly reduced post operation.

Muscle activation and rating of perceived exertion of typically developing children during DRY and aquatic treadmill walking.

Aquatic treadmill gait training is a poorly understood rehabilitation method that alters bodyweight support, increases lower limb resistance, and assists with postural stability. This training could be an attractive tool for clinical populations with balance control issues or limited weight-bearing prescriptions for the lower limb. As a first step, the purpose of this study was to quantify differences in mean muscle activity of the tibialis anterior, rectus femoris, medial gastrocnemius, and semitendinosus, and perceived exertion (RPE) in typically developing children (7:8 M:F, age=11.3±4.1years, 1.46±0.18m, and 44.2±16.8kg) during dry and aquatic treadmill walking at 75%, 100%, and 125% self-selected speed. We hypothesized that the greatest mean muscle activity, normalized to percent maximum voluntary contraction and averaged across all strides, would be observed during 125% dry treadmill walking and that aquatic treadmill walking would produce lower RPE. Overall, aquatic treadmill walking reduced mean medial gastrocnemius activity by 50.2% (padj<0.001), increased mean rectus femoris activity at least 32.8% (padj<0.006), and produced 78.0% (padj=0.007) greater RPE compared to dry treadmill walking. This study provides normative pediatric data for future aquatic treadmill walking studies in clinical populations to help inform gait rehabilitation protocols.

Broader Estimates of Gastrocnemius Activity Generated a More Representative Cocontraction Index: A Study in Pediatric Population.

The electromyography (EMG) cocontraction index (CCI) given by the antagonistic/agonistic Root Mean Square (RMS) amplitude ratio of the same muscle is a qualified biomarker used for spastic cocontraction quantification and management in cerebral palsy children. However, this normative EMG ratio is likely subject to a potential source of errors with biased estimates when measuring the gastrocnemius plantar flexors activity. Due to the uneven distribution of electrical activity within the muscle volume, cocontraction levels can be misestimated, if EMGs are obtained from the sole traditional bipolar sensor location recommended by SENIAM. This preliminary study, on 10 healthy children (mean age 10 yr), investigated whether surface EMG detected proximally and distally via two pairs of bipolar electrodes, within the medial gastrocnemius (MG), provides a significant difference in CCI estimates during non-dynamic (isometric dorsiflexion) and dynamic (swing phases of gait) conditions. Gait cycles were extracted from Inertial Measurement Unit sensors. Medial gastrocnemius activity was greater distally than proximally during plantar flexion when it acts as an agonist (~24±18%) and it was greater proximally during dorsiflexion (~23±9%) when it is acting as an antagonist. As a direct consequence, CCI estimates from the conventional sensor location were significantly different (~36%) from the CCIs computed by considering broader MG regions. This difference arose in all subjects during isometric efforts and in two of 10 healthy children during the swing phase of gait who presented cocontraction patterns (p<0.05). EMG bipolar sampling encompassing proximal and distal gastrocnemius muscle regions may reduce bias in CCI computation and provide a more representative and accurate cocontraction index that is especially important for comparisons to the diseased state.

Under pressure: design and validation of a pressure-sensitive insole for ankle plantar flexion biofeedback during neuromuscular gait training.

Electromyography (EMG)-based audiovisual biofeedback systems, developed and tested in research settings to train neuromuscular control in patient populations such as cerebral palsy (CP), have inherent implementation obstacles that may limit their translation to clinical practice. The purpose of this study was to design and validate an alternative, plantar pressure-based biofeedback system for improving ankle plantar flexor recruitment during walking in individuals with CP. Eight individuals with CP (11-18 years old) were recruited to test both an EMG-based and a plantar pressure-based biofeedback system while walking. Ankle plantar flexor muscle recruitment, co-contraction at the ankle, and lower limb kinematics were compared between the two systems and relative to baseline walking. Relative to baseline walking, both biofeedback systems yielded significant increases in mean soleus (43-58%, p < 0.05), and mean (68-70%, p < 0.05) and peak (71-82%, p < 0.05) medial gastrocnemius activation, with no differences between the two systems and strong relationships for all primary outcome variables (R = 0.89-0.94). Ankle co-contraction significantly increased relative to baseline only with the EMG-based system (52%, p = 0.03). These findings support future research on functional training with this simple, low-cost biofeedback modality.

A biomechanical approach to study lunge in fence athletes

Fencing requires neuromuscular coordination, strength, and power, and it has a high impact on the musculoskeletal system [1–5]. The lunge is the most important strike action. It is produced with explosive power and surprises the opponent to score points. The lunge starts from the armed arm, which must be moved as quickly as possible toward the opponent, combined with lower body movements to provide a boosting action [4]. The present study aims at assessing kinematics and electromyographic differences between tasks and categories. The participants were 28 male and female, élite and recreational fencers, practicing foil and épée. The age ranged from 8 to 35 years old. Anthropometric and biographical information were taken. Kinematics data were acquired using a wearable inertial system BTS G-SENSOR2, positioned on the L5 vertebra. Four wearable EMG probes BTS FREEEMG 1000 were used to detect EMG signal of Deltoideus Anterior (DLTA) and Rectus femoris (RF) both on the armed side; Erector Longissimus muscle (LONG) and Gastrocnemius medialis (GAM), on the opposite one. These devices were synchronized by the acquisition software BTS EMG-Analyzer. Muscles' MVC and two trials of lunge (AF), step forward lunge (AA) and step backward lunge (DA) were taken. Data were processed with MATLAB and Tracker. VWilcoxon’s effect size for continuous variables and prevalence differences for categorical ones. Age and anthropometric measures were statistically different between the two categories (P < 0.05). No statistically significant differences are observed between the sexes, excluding thigh circumference (P < 0.05). The normalized distances and x-axis ROM between tasks and the y-axis ROM in the second trial (AA), the mean normalized muscle activation of DLTA, RF, and GAM between categories were statistically different (P <0.05). No significant statistical differences in muscle activation patterns were observed between different categories. Each correlation coefficient was interpreted based on a previously described classification using similar variables: 0-0.4 (weak), 0.4-0.7 (moderate), and 0.7-1.0 (strong). Table 1 summarizes the results observed from the correlation, the direction of the arrow stands for the direction of correlation (positive or negative), while the number of arrows is the intensity of correlation (weak, moderate, or strong). It is important to emphasize the negative correlation between lunge time and activation intensity of the LONG muscle, as well as the positive correlation between lunge distance and activation intensity of the GAM muscle. Differences have been observed in some kinematic and electromyographic parameters among categories and tasks. No substantial difference in muscle patterns is observed between different categories. Furthermore, correlations have emerged between muscular activity and spatiotemporal variables of movement: a greater rapidity of movement is associated with greater activity of the LONG, because it is balance responsible. A longer lunge distance is related to a greater activity of the GAM (boosting muscle).