Differences In Muscle Activity Research Articles

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.

Characterizing Muscle Activity in Soccer Players with a History of Hamstring Strain Injuries during Accelerated Sprinting.

This study aimed to characterize muscle activity in male soccer players with a history of hamstring strain injuries (HSI) during accelerated sprinting. Thirteen patients each in the HSI group (history of HSI) and in the healthy group (with no history of HSI) were included. 26 male soccer players of which 13 with and 13 without HSI history were included in this study. Ten muscles were evaluated on electromyography activity during overground sprinting. The testing protocol consisted of a maximal sprint over a distance of 30 meters. One running stride was divided into the early stance phase, late stance phase, early swing phase, mid-swing phase, and late swing phase, and the average muscle activity per phase and the timing of the peak root-mean-square value appearance during each stride were calculated. Statistical analysis was performed using repeated-measures two-way ANOVA (group × phase), and multiple comparison tests were performed using the Bonferroni method when the interaction or main effect was significant. The statistical significance level was set at p < 0.05. Gluteus maximus (Gmax), gluteus medius (Gmed), and external oblique (EO) showed activity differences based on HSI history. Gmax was 30% lower, EO was 20% lower, and Gmed was 40% higher in HSI group. This study suggests that, despite previous findings that HSI is most likely during the late swing phase, the HSI group shows a higher injury risk in the early stance phase. This is due to differences in trunk and gluteal muscle activity between the late swing and early stance phases compared to the healthy group. In summary, HSI group had lower activity in the muscles contributing to trunk instability, especially EO and Gmax, before and after ground impact during accelerated sprinting, compared to Healthy.

Comparative analysis of biomechanical characteristics between the new Tai Chi elastic band exercise for opening and closing movement and elastic band resistance training for the reverse fly movement.

The objective of this study was to compare and analyze the representative opening and closing movement of Tai Chi elastic band exercise with the reverse fly movement of elastic band resistance training. The aim was to explore the biomechanical differences between the two exercises and provide theoretical support for the application of Tai Chi elastic band exercise in health intervention. A total of 26 male participants were recruited and randomly divided into two groups in a 1:1 ratio. There were 13 participants in each Tai Chi elastic band exercise group and elastic band resistance training group. Both groups of participants used an elastic band to perform movement in the experiment. Experimental data were collected using the Vicon infrared motion capture system and Delsys surface EMG system. The AnyBody software was utilized to simulate the creation of a musculoskeletal model for both exercises. The study found that the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angle and flexion angle of the shoulder joint, as well as normalized RMS of the anterior deltoid and triceps brachii, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited greater elbow flexion angle, elbow flexion torque, and muscle strength of the infraspinatus, coracobrachialis, biceps brachii, brachialis and brachioradialis, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angular velocity of the shoulder joint and a lower normalized RMS of the posterior deltoid, compared to the elastic band resistance training group (P < 0.05). (1) The opening and closing movement of Tai Chi elastic band exercise is characterized by a large elbow flexion angle, a small shoulder joint horizontal angle and flexion angle, and a slow and uniform speed of movement. The reverse fly movement of elastic band resistance training is characterized by a large horizontal abduction angle of the shoulder joint, a large flexion angle of the shoulder joint, a small flexion angle of the elbow joint, and a fast and uneven speed. (2) The opening and closing movement exerts a greater torque on the elbow flexion, while the reverse fly movement exerts a greater torque on the shoulder joint horizontal abduction and external rotation. (3) The opening and closing movement provide greater stimulation to the infraspinatus, coracobrachialis, and elbow flexor, while the reverse fly movement provides greater stimulation to the posterior deltoid, anterior deltoid, subscapularis, and elbow extensor. In summary, the variation in joint angle, joint angular velocity, and hand position could be the factor contributing to the differences in joint torque and muscle activity between the opening and closing movement of Tai Chi elastic band exercise and the reverse fly movement of elastic band resistance training.

Biomechanical analysis of the snatch technique for elite and varsity weightlifters

Understanding the importance of movement asymmetries and variations in technique proficiency across different level of weightlifters is crucial. The purpose of this study was to examine differences in joint kinematics, muscle activation, and barbell parameters between elite and varsity weightlifters during the snatch utilizing integrated 3D motion capture and EMG systems. In addition, it analyzes symmetries in joint kinematics and muscle activation in both groups. Ten female participants, comprising 5 elite and 5 varsity weightlifters, along with thirteen male participants, consisting of 6 elite and 7 varsity weightlifters during snatch were measured. Several asymmetries in posture and muscle activation were identified in both elite and varsity weightlifters. In addition, elite weightlifters exhibited significantly more flexed knees than varsity counterparts (p < 0.05) at the conclusion of the second pull and at the highest position of the barbell. Furthermore, significantly lower activity in gluteus maximus was detected in elite weightlifter at the highest point of the barbell than in the varsity groups (p < 0.05). Moreover, elite males achieved a lower maximum height for the barbell compared to varsity males (p = 0.006). Furthermore, elite females demonstrated less horizontal displacement (D2x) (p = 0.005) than varsity counterparts. Varsity women presented significantly lower horizontal velocity (p = 0.003) at the conclusion of the second pull than varsity counterparts. Despite several asymmetries detected, those may not be critical factors in achieving a successful snatch lift, given that all weightlifters successfully completed the lift. However, variations in posture and muscle activation may still be associated with improvements in technique proficiency across different levels of weightlifters.

Agreement and Consistency of Absolute and Relative Corticospinal Stimulus-Response Curves for Upper, Lower, and Axial Musculature in Healthy Adults.

To assess the agreement and consistency of absolute and relative stimulus-response curve (SRC) parameter estimates for upper extremity, lower extremity, and axial muscles. Thirty (15 W, age: 27.0 ± 6.3 y, height: 171.9 ± 8.9 cm, weight: 80.2 ± 19.3 kg) healthy adults completed absolute (5% to 100% stimulator output) and relative (65% to 160% motor threshold) SRCs of the first dorsal interosseous, vastus lateralis, and rectus abdominis during submaximal isometric contractions. Mean motor-evoked potential amplitudes were fit with nonlinear regression to derive MEPmax, V50, and slope. Absolute agreement and consistency were assessed with ICCs, Cronbachs alphas, and Bland-Altman plots. Independent t-tests were used to examine differences in motor threshold, physical activity, strength, and muscle activity among participants with valid and invalid SRC parameters. Absolute and relative SRCs displayed good agreement and consistency for MEPmax and V50 but not slope. Motor thresholds were lower among participants with valid absolute SRCs for the rectus abdominis and vastus lateralis. Motor threshold, physical activity, strength, and muscle activity did not differ among those with valid and invalid parameters for all relative SRCs and absolute SRCs for the first dorsal interosseous. Absolute and relative SRCs produce similar MEPmax and V50 estimates in the first dorsal interosseous, vastus lateralis, and rectus abdominis. The validity of absolute and relative SRC results may differ depending on individual characteristics and tested muscles.

Bone and muscle differences in children and adolescents with type 1 diabetes: The mediating role of physical activity

Children with type 1 diabetes (T1D) experience an increased risk of fracture, which may be related to altered bone development. We aimed to assess differences in bone, muscle and physical activity (PA), and explore if better muscle and PA measures would mitigate bone differences between children and adolescents with T1D and typically developing peers (TDP). We matched 56 children and adolescents with T1D (mean age 11.9 yrs) and 56 TDP (11.5 yrs) by sex and maturity from 171 participants with T1D and 66 TDP (6-17 yrs). We assessed the distal radius and tibia with high-resolution peripheral quantitative computed tomography (HR-pQCT), and the radius and tibia shaft bone and muscle with pQCT. We also measured muscle function from force-related measures in neuromuscular performance tests (push-up, grip test, countermovement and long jump). We compared PA based on questionnaire scores and accelerometers between groups. Bone, muscle, and neuromuscular performance measures were compared using MANOVA. We used mediation to explore the role of PA and muscle in bone differences. Children and adolescents with T1D had 6–10 % lower trabecular density, bone volume fraction, thickness and number at both distal radius and tibia, and 11 % higher trabecular separation at the distal radius than TDP. They also had 3–16 % higher cortical and tissue mineral density, and cortical thickness at the distal radius, 5–7 % higher cortical density and 1–3 % higher muscle density at both shaft sites compared to TDP. PA mediated the between-group difference in trabecular number (indirect effect −0.04) at the distal radius. Children and adolescents with T1D had lower trabecular bone density and deficits in trabecular micro-architecture, but higher cortical bone density and thickness at the radius and tibia compared to TDP. They engaged in less PA but had comparable muscle measures to those of TDP. PA participation may assist in mitigating deficit in trabecular number observed in children and adolescents with T1D.

Trunk muscle activation of core stabilization exercises in subjects with and without chronic low back pain.

Weakness and atrophy in trunk muscles have been associated with chronic low back pain (CLBP). This study aimed to identify isometric exercises resulting the highest trunk muscle activity for individuals with and without CLBP. Fourteen males with CLBP and 15 healthy age-matched healthy subjects were recruited for this study. Muscle activity during maximal voluntary isometric contraction (MVIC) was measured for a comparative reference with surface electromyography (sEMG) from six trunk muscles. Thereafter maximum EMG amplitude values were measured during eleven trunk stability exercises. The maximal EMG activity in each exercise relative to the MVICs was analyzed using generalizing estimating equations (GEE) models with the unstructured correlation structure. The GEE models showed statistically significant differences in muscle activity between exercises within both groups (p< 0.001), with no significant differences between groups (p> 0.05). The highest muscle activity was achieved with the hip flexion machine for multifidus, side pull with a resistance band for lumbar extensors, side and single-arm cable pull exercises for thoracic extensors, rotary plank and the hip flexion machine for abdominal. This study found five isometric trunk exercises that exhibited highest muscle activity depending on muscle tested, with no significant difference between individuals with and without CLBP.

Differences in Muscle Activity during Horseback Riding Trotting and Walking in Patients with Chronic Back Pain

Differences in Muscle Activity during Horseback Riding Trotting and Walking in Patients with Chronic Back Pain

Effect of scapular posterior tilting exercise on scapular muscle activities in men and women with a rounded shoulder posture

Round-shoulder posture (RSP) is a common postural condition, characterized by protraction, downward rotation, anterior tilting and internal rotation of the scapula. RSP can lead to shoulder dysfunction. Different methods have been proposed for rehabilitating and correcting the altered posture in RSP including stretching, strengthening exercises, and shoulder brace or taping. However, the findings are controversial and studies are ongoing to develop more effective method. The present study is aimed at investigating the effects of scapular posterior tilting (SPT) exercise in different support positions on scapular muscle activities in men and women with RSP. In a prospective observational clinical study, we assessed demographic, basic clinical parameters and study variables of the subjects with RSP (n = 20) (men/women = 9/11) attending Daegu University in Gyeongsan, South Korea. To do so, we compared electromyographic (EMG) activities of lower trapezius and serratus anterior muscles between men and women with RSP during SPT exercise on four different support surfaces to determine any difference in the EMG activities. The results revealed that women showed significant differences in EMG activities in the lower and left upper trapezius and serratus anterior muscles, while men showed significant differences in EMG activity only in the lower trapezius muscle during SPT exercise on four different surfaces (P < 0.05). The post-hoc analysis revealed significantly greater EMG activity values in the lower trapezius and serratus anterior muscles during SPT exercise on the upper body unstable surface and whole-body unstable surface (p < 0.05). Independent t-tests after the Bonferroni correction showed no significant differences in muscle activities between men and women on the four different surfaces (p > 0.0125).

Effects of differences in femoral anteversion and hip flexion angle on hip abductor muscles activity during clam exercise in females.

This study aimed to determine differences in the hip abductor muscle activity during clam exercise at different hip flexion and femoral anteversion angles. Thirty healthy females were divided into two groups based on the femoral anteversion angle: the excessive femoral anteversion group and the normal group. Clam exercise was performed at three different hip flexion angles (60°, 45°, and 30°). Tensor fascia latae, gluteus medius, and superior portion of gluteus maximus activities were measured during the exercise, and the results were normalized to the activity during maximum voluntary isometric contraction to calculate the gluteal-to-tensor fascia latae muscle activation index. The superior portion of gluteus maximus activities at a hip flexion of 60° and 45° were greater than that at 30°. The excessive femoral anteversion group had a lower gluteal-to-tensor fascia latae muscle activation index than the normal group; the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° was higher than that at 45°, and the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° and 45° were higher than that at 30°. Therefore, the femoral anteversion angle and hip joint position were related to the activity of the hip abductor muscles during clam exercise. These findings may provide a rationale for instructing exercises to maximize the activity of the hip abductor muscles in individuals with an excessive femoral anteversion angle.

Age- and Parkinson-related differences in trunk and lower-limb muscle activation during four balance tasks: A case-control pilot study

BackgroundPoor postural control has been reported in people with Parkinson's disease, which could be explained by the changes in muscular activation patterns related to antigravitational muscles. This study aims to measure the muscle activation of antigravitational muscles during balance tasks in individuals, with and without Parkinson's. MethodsSixteen (16) participants (9 with Parkinson's), aged ≥65 yrs., performed 2 × 30-s trials of 4 balance tasks (bipodal and semi-tandem opened eyes and closed eyes) on a force platform (center of pressure measurement); while surface electromyography measurements were obtained bilaterally on the multifidus at L5, biceps femoris and medialis gastrocnemius. Electromyography amplitude analysis was processed by the Root Mean Square (250 ms window epochs) and normalized by the peak of activation during the balance task, to determine each muscle's activity level. FindingsThe Parkinson's group reported lower muscle activation than control across tasks (in mean for multifidus = 8%, biceps femoris = 16%, gastrocnemius = 7%), although not statistically significant. Parkinson's reported significantly poorer postural control than control, mainly for the center of pressure sway ellipse area (p = 0.016) from challenge balance tasks such as semi-tandem. InterpretationPoor postural control was confirmed in the Parkinson's group, but not significantly associated by the changes from muscle activation of trunk and lower limbs, during balance performance.

Exploring lower limb muscle activity and performance variations during instrumented Sit-to-Stand-to-Sit in sedentary individuals: Influence of limb dominance and testing modalities

Purposeto explore lower limb muscle activity concerning limb dominance, as well as variations in force and power during the standing up and sitting down phases of the instrumented sit-to-stand-to-sit test in sedentary individuals, across isokinetic and isotonic modalities. Methods33 sedentary individuals underwent testing using a functional electromechanical dynamometer in both isokinetic and isotonic modes, accompanied by surface electromyography. ResultsIn the isokinetic mode, the non-dominant gastrocnemius medialis and vastus medialis exhibited significantly (p < 0.05) higher muscle activity values during the standing up and sitting down phase compared to dominant counterparts. In the isotonic mode standing up phase, significant differences in muscle activity were noted for non-dominant gastrocnemius medialis, vastus medialis, and biceps femoris compared to their dominant counterparts. The sitting down phase in isotonic mode showed higher muscle activity for non-dominant vastus medialis compared to dominant vastus medialis. Regard to performance outcomes, significantly lower (p < 0.0001) values were observed for standing up (12.7 ± 5.1 N/kg) compared to sitting down (15.9 ± 6.1 N/kg) peak force, as well as for standing up (18.7 ± 7.8 W/kg) compared to sitting down (25.9 ± 9.7 W/kg) peak power in isokinetic mode. In isotonic mode, lower values were found for sitting down (6.5 (6.3–7.1) N/kg) compared to standing up (7.8 (7.3–8.9) N/kg) peak force and for sitting down (18.5 (13.2–21.7) W/kg) compared to standing up (33.7 (22.8–41.6) W/kg) peak power. ConclusionsLimb dominance influences lower-limb muscle activity during the instrumented sit-to-stand-to-sit test, and the choice of testing mode (isokinetic or isotonic) affects muscle engagement and performance outcomes.

Differences in muscle activity of extrinsic and intrinsic foot muscles in toe grip and push-down movements of the great toe

Toe flexor strength is generated primarily by the flexor hallucis longus (FHL) of the extrinsic foot muscles (EFMs) and the plantar intrinsic foot muscles (PIFMs) of the great toe. Toe flexion methods can be broadly classified into toe grip (TG) and toe push-down (TP). Additionally, TP's interphalangeal joint (IPJ) position may influence the FHL and PIFMs activity ratios. This study aimed to elucidate the differences in the muscle activity and muscle activity ratios of the FHL and AbdH during TG, TP with IPJ flexion (TPIF), and TP with IPJ extension (TPIE).Surface electromyography and a custom-made instrument were used to measure the FHL and AbdH muscle activity during TG, TPIF, and TPIE of the great toe in 28 healthy men. The muscle activity and AbdH/FHL muscle activity ratio in the three conditions were statistically compared.The FHL activity was significantly higher during TG and TPIF than during TPIE. The AbdH muscle activity was significantly higher during TPIF and TPIE than that during TG. The AbdH/FHL muscle activity ratio was significantly higher for TPIE, TPIF, and TG in that order.This study showed that the FHL and AbdH muscle activity differed depending on the TG and TP of the great toe, and that the AbdH/FHL muscle activity ratio was different in the IPJ position. These results suggest that selecting a toe flexion method according to the target muscle when measuring and training the great toe flexor strength is important.

Gender differences in neck muscle activity during near-maximum forward head flexion while using smartphones with varied postures

Women frequently express heightened neck discomfort even though they exhibit smaller neck flexion (NF) during smartphone use. Differences in natural posture while using smartphones may result in varying muscle activation patterns between genders. However, no study focused on this issue. This study investigated the influence of gender on neck muscle activity and NF when using smartphones, ranging from slight (20°) to nearly maximal forward head flexion, across different postures. We analyzed smartphone usage patterns in 16 men and 16 women and examined these behaviors across different scenarios: standing, supported sitting, and unsupported sitting, at 20°, 30°, 40°, and the maximum head angles. During data collection, muscle activity was measured, expressed as a percentage of the maximum voluntary contraction (%MVC), in the cervical erector spinae (CES) and upper trapezius (UTZ), along with NF. Results show significant influences of gender, head angle, and posture on all measures, with notable interactions among these variables. Women displayed higher muscle activities in CES and UTZ, yet exhibited lesser NF, while using smartphones in both standing (12.3%MVC, 10.7% MVC, and 69.0°, respectively) and unsupported sitting (10.8%MVC, 12.3%MVC, and 71.8°, respectively) compared to men (standing: 9.5%MVC, 8.8%MVC, and 76.1°; unsupported sitting: 9.7%MVC, 10.8%MVC, and 76.1°). This study provides a potential rationale for gender-related disparities in injury outcomes, emphasizing that women experience higher neck and shoulder discomfort level, despite their smaller NF during smartphone use, as found in previous research. Additionally, the cervical flexion-relaxation phenomenon may occur when the head angle exceeded 40°. The near-maximum head angle during smartphone use might induce the cervical flexion-relaxation phenomenon, potentially aggravating neck issues. We recommend limiting smartphone usage postures that exceed the near-maximum head angle, as they are commonly adopted by individuals in the daily smartphone activities.

Impairments in peroneal muscle size and activation in individuals with patellofemoral pain in weight-bearing position.

Patellofemoral pain (PFP) is characterized by chronic pain in the anterior aspect of the knee during loading activities. Many studies investigating muscle morphology changes for individuals with PFP focus on the proximal joints, however, few studies have investigated muscles of the foot and ankle complex. This study aimed to explore the differences in peroneal muscle size and activation between individuals with PFP and healthy controls using ultrasound imaging in weight-bearing. A case-control study in a university lab setting was conducted. Thirty individuals with PFP (age: 20.23±3.30years, mass: 74.70±27.63kgs, height: 161.32±11.72cm) and 30 healthy individuals (age: 20.33±3.37years, mass: 64.02±11.00kgs, height: 169.31±9.30cm) participated. Cross-sectional area (CSA) images of the peroneal muscles were taken in non-weight bearing and weight-bearing positions. The functional activation ratio from lying to single-leg standing (SLS) was calculated. There was a statistically significant (p=0.041) group (PFP, healthy) by position (non-weight-bearing, weight-bearing) interaction for the peroneal muscle CSA with a Cohen's d effect size of 0.2 in non-weight-bearing position and 0.7 in weight-bearing position. The functional activation ratio for the healthy group was significantly more (p=0.01) than the PFP group. Peroneal muscles were found to be smaller in size in those with PFP compared to the healthy subjects in the weight-bearing SLS position. This study found that those with PFP have lower activation of peroneal muscles in functional position.

Neural Respiratory Drive During Different Dyspnea Relief Positions and Breathing Exercises in Individuals With COPD.

When the work load of the respiratory muscles increases and/or their capacity decreases in individuals with COPD, respiratory muscle activation increases to maintain gas exchange and respiratory mechanics, and perception of dyspnea occurs. The present study aimed to compare diaphragm and accessory respiratory muscle activation during normal breathing, pursed-lip breathing, and breathing control in different dyspnea relief positions, supine and side lying. A cross-sectional study design was used. Sixteen individuals with COPD age between 40-75 y were included. Pulmonary function was evaluated by spirometry, muscle activation by surface electromyography, and dyspnea by the modified Borg scale. Muscle activation was measured in the diaphragm, scalene, sternocleidomastoid, and parasternal muscles. The evaluation was made in the dyspnea relief positions (sitting leaning forward, sitting leaning forward at a table, leaning forward with back against a wall, standing leaning forward, and high lying), seated erect, supine, and side lying. There were significant differences between the 8 positions (P < .001). There was no significant difference in muscle activation between sitting leaning forward and sitting leaning forward at a table position with analyzing post hoc test results (P > .99 for each muscle). However, muscle activation was lower in these 2 positions than in the other positions (P < .001 for each muscle). Muscle activation was greater in the supine position than in the other positions (P < .001 for each muscle). No difference was observed in muscle activation between the seated erect, leaning forward with back against a wall, standing leaning forward, high-lying, or side-lying positions (P > .05 for each muscle with a minimum P value of .09). The use of sitting leaning forward and sitting leaning forward at a table positions together with breathing control may help people with COPD to achieve more effective dyspnea relief and greater energy efficiency.

Comparison of trunk muscle activity during lumbar stabilization exercises on stable and unstable surfaces.

Lumbar stabilization exercises (LSE) provide dynamic trunk stability, promote muscle strength and endurance, and improve low back pain rehabilitation and performance. To clarify the differences in trunk muscle activity during LSEs on stable and different unstable surfaces. Fifteen healthy males performed three exercises (elbow-toe, hand-knee, and side bridge) on stable (floor) and unstable surfaces. Muscle activity of the bilateral rectus abdominis, internal oblique, external oblique, and erector spinae were recorded. Data were compared using the Friedman test. Pairwise comparisons were performed using Wilcoxon's signed rank test if significant differences were observed. In the elbow-toe exercise, muscle activity of the rectus abdominis and right internal oblique increased in the following order: floor, low-difficulty, and high-difficulty unstable surface. In the hand-knee exercise, muscle activity of the internal oblique on the lower-extremity elevated side, external oblique, and erector spinae on the upper-extremity elevated side were greater on unstable surface exercise performance. In the side bridge exercise, rectus abdominis muscle activity was highest on a high-difficulty unstable surface. Trunk muscle activity increased during exercise on unstable surfaces. Since the effects of unstable surfaces vary depending on muscle and exercise types, exercise difficulty and surface stability must be considered accordingly.

Influence of Amputation on Kinetic Chain Musculature Activity During Basic and Modified Core Exercises.

Core strength is vital for athletic performance, and many more exercises that involve the kinetic chain have been designed for able-bodied athletes. Disabilities that impair the kinetic chain can reduce the effectiveness of strength training. However, the impact of amputation on core strength training of people with disabilities and its underlying mechanism remains unclear. This study aimed to evaluate the muscle activation patterns and levels in athletes with amputation during 4 basic and modified weight-bearing core strength-training exercises. Fifteen elite athletes with unilateral amputation (170.6 [7.3]cm; 63.9 [11.9]kg; 25.9 [5.3]y) volunteered for this study. Surface electromyography was used to measure the muscle activity mainly in the lumbopelvic-hip complex-stabilizing muscles during 4 kinetic chain trunk exercises with and without modifications. The significance level was set at α = .05. The results showed a significant difference in muscle activation between different body sides (P < .05). Specifically, amputation on the support position resulted in a diagonal pattern of muscle activation, and amputation on the free distal segments resulted in a unilateral dominant pattern with higher activation in muscles on the nonamputated side (P < .05). Modifications led to significant decreases in muscle activation asymmetry index (P < .05). Amputation caused muscle activation asymmetry and 2 activation patterns. Modifications by enhancing proximal stability and adjusting distal loading effectively reduced the asymmetry of muscle activation. Coaches and clinicians can use these results to tailor exercises for athletes with disabilities in training and rehabilitation.

Differences on Thigh Muscles&amp;apos; Activity by Types of Squat

OBJECTIVES Thigh strength has many features in our life. Many people perform vary squat types to stimulate different thigh muscles. However, there is a lack of information on which squat is the most effective on targeted muscles. Therefore, the purpose of this study was to compare thigh muscles’ activity by squat types and suggest the correct squat for strengthening thigh.METHODS Total of 20 men and women (age: 23.9±1.5yrs, height: 173.3±6.6cm, weight: 75.1±13.2kg, BMI: 24.9±3.1kg/m&lt;sup&gt;2&lt;/sup&gt;) who had no musculoskeletal pathologies within last one year, and had weight training experience for more than 1 year were participated. Squat types were classified into standard (SS), narrow (NS), wide (WS), jump (JS), and Smith machine squats (SMS). Surface electromyography was used to collect the muscle activity of the thigh during three repetitions of each squat without weights. Time points during squat are defined as follows: E1 (start), E2 (maximum knee flexion, MKF), E3 (returned), P1 (from start to MKF), and P2 (from MKF to return). Repeated measured ANOVA was used to verify differences in lower limb muscle activity between squat types.RESULTS At the E2, significant differences were found in RF (p=.00) and ST (p=.00). In the P1, significant differences were found in RF (p=.00), VL (p=.00), and BF (p=.02). In the P2, significant differences were found in RF (p=.00), VM (p=.00), and ST (p=.01).CONCLUSIONS For more activity of both quadriceps and hamstrings, plyometric-based JS is the most effective squat, but by considering the performer's lack of exercise experience, postural control may not be performed correctly which may lead to injury. In addition, stable squat using the Smith machine should be considered and the intensity, number of repetitions, and weight should be carefully set according to type of squat.

Identification of the Biomechanical Response of the Muscles That Contract the Most during Disfluencies in Stuttered Speech.

Stuttering, affecting approximately 1% of the global population, is a complex speech disorder significantly impacting individuals' quality of life. Prior studies using electromyography (EMG) to examine orofacial muscle activity in stuttering have presented mixed results, highlighting the variability in neuromuscular responses during stuttering episodes. Fifty-five participants with stuttering and 30 individuals without stuttering, aged between 18 and 40, participated in the study. EMG signals from five facial and cervical muscles were recorded during speech tasks and analyzed for mean amplitude and frequency activity in the 5-15 Hz range to identify significant differences. Upon analysis of the 5-15 Hz frequency range, a higher average amplitude was observed in the zygomaticus major muscle for participants while stuttering (p < 0.05). Additionally, when assessing the overall EMG signal amplitude, a higher average amplitude was observed in samples obtained from disfluencies in participants who did not stutter, particularly in the depressor anguli oris muscle (p < 0.05). Significant differences in muscle activity were observed between the two groups, particularly in the depressor anguli oris and zygomaticus major muscles. These results suggest that the underlying neuromuscular mechanisms of stuttering might involve subtle aspects of timing and coordination in muscle activation. Therefore, these findings may contribute to the field of biosensors by providing valuable perspectives on neuromuscular mechanisms and the relevance of electromyography in stuttering research. Further research in this area has the potential to advance the development of biosensor technology for language-related applications and therapeutic interventions in stuttering.