Search Results (86)

This study aims to investigate asymmetries in muscle activation and co-contraction of main lower limb muscles during flamenco Zap-3 footwork with consideration of the footwork speed and dancer proficiency. Twelve flamenco dancers participated, including six professionals and six amateurs. Each participant performed the Zap-3 sequence under three speed conditions: 160 beats per minute (bpm), 180 bpm and the fastest speed level (F). The normalized surface electromyography was recorded in the gastrocnemius medialis (GM), biceps femoris (BF), tibialis anterior (TA) and rectus femoris (RF) in the dominant (DL) and non-dominant leg (NDL). The co-contraction index was also calculated for selected muscle pairs. The results showed that significant asymmetries occurred only in professional dancers and exclusively at the F speed level. Specifically, the value of the GM in the NDL was higher than that of the DL (p < 0.05, d = 1.97); the value of the BF in the DL was higher than that of the NDL (p < 0.05, d = 1.86) and the co-contraction index of BF/RF in the DL was higher than that of the NDL (p < 0.05, d = 1.87). Understanding these asymmetries may help to inform individualized training strategies aimed at optimizing performance and reducing potential risks. Full article

Background: This study investigates differences in muscle co-contraction and peak electromyography (EMG) activity between novice and advanced Taekwondo athletes during consecutive roundhouse (bandal chagui) kicks, examining the influence of body composition and experience level. Methods: Sixteen Taekwondo athletes (12 males, 4 females; mean age: 20.5 ± 4.3 years) were divided into novice (n = 8) and advanced (n = 8) groups. Muscle co-contraction indices and peak EMG activity across 15 consecutive kicks were assessed in key lower limb muscles, including the biceps femoris (BF), lateral gastrocnemius (LG), rectus femoris (RF), soleus (SO), semitendinosus (ST), tibialis anterior (TA), vastus lateralis (VL), and vastus medialis (VM). Results: Advanced athletes exhibited significantly higher co-contraction indices in BF–RF, VM–BF, and SO–TA pairs (p < 0.05) and increased peak EMG trends in the BF and LG (p < 0.05). Novice athletes showed significantly reduced peak EMG increases in the RF, VM, and VL. EMG trends were influenced by body composition, with principal component analysis indicating that higher fat mass and lower muscle mass were associated with greater variations in muscle activation. Conclusions: These findings suggest that advanced athletes refine motor control through increased co-contraction, improving stability and efficiency, while novices exhibit less optimized coordination patterns. This study provides insights into the neuromechanical adaptations associated with expertise development in Taekwondo. Full article

Background and Objectives: Anterior cruciate ligament (ACL) injury rates remain high and have a significant impact on female football players. This study aims to evaluate knee kinematics and lower limb muscle activity in players at risk of ACL injury compared to healthy players through three side-cutting tests. It also investigates how the amplitude of a change in direction influences stabilization parameters. Materials and Methods: A cross-sectional case–control study was conducted with 16 second division female futsal players (23.93 ± 5.16 years), divided into injured (n = 8) and healthy groups (n = 8). Injured players had a history of non-contact knee injury involving valgus collapse, without undergoing surgical intervention. Three change of direction tests, namely the Change of Direction and Acceleration Test (CODAT), Go Back (GOB) test, and Turn (TURN) test, were used for evaluation. The peak and range of knee joint angles and angular velocities across three planes, along with the average rectified and peak envelope EMG signals of the Biceps Femoris (BF), Semitendinosus (ST), Vastus Medialis (VM), and Lateral Gastrocnemius (LG), were recorded during the preparation and load phases. Group differences were analyzed using two-factor mixed-model ANOVA with pairwise comparisons. Statistical significance was set at p < 0.05. Results: Injured players demonstrated lower external tibial rotation angular velocity and a greater range of motion in tibial external rotation compared to healthy players. Additionally, the injured group showed significantly higher average rectified muscle activity in VM and LG both increased by 4% during the load phase. The CODAT and TURN tests elicited higher BF and VM muscle activity, compared to the GOB test. The TURN test also showed greater extension angular velocity in the sagittal plane. Conclusions: The results revealed differences in knee kinematics and muscle activity between players at risk of ACL injury and healthy players, influenced by the amplitude of directional changes. Players altered transverse plane mechanics and increased VM and LG activation during LOAD may reflect a dysfunctional motor pattern, while the greater sagittal plane angular velocity and VM and BF activation from the CODAT and the TURN test highlight their higher potential to replicate ACL injury mechanisms compared to the GOB test. Full article

Background/Objectives: The adverse effects of low gravity on human physiology are well documented; however, much of the literature is directed at changes which occur in microgravity (µg: weightlessness) with relatively less documented on changes in hypogravity (<1 g; >µg: gravity less than Earth’s but more than microgravity). Somatosensation and neuromuscular control may be of particular importance for astronauts as they prepare for future missions to walk on the Moon. This study aimed to explore the effect of reduced weight bearing (to simulate conditions of hypogravity) on ankle somatosensation, lower-limb muscle activity, tone, and stiffness, compared to full weight bearing. Methods: Participants completed an ankle somatosensory acuity task (active movement extent discrimination assessment [AMEDA]) in two body positions: (1) upright standing (1 g), and (2) in a head-elevated supine, semi-weight bearing (0.16 g) position using a custom-built inclined “wedge bed”. The second position induced ~16% body weight on to the plantar aspect of the feet, simulating that of lunar gravity. We compared the AMEDA scores between the two positions. Lower-limb muscle activity was recorded via surface EMG throughout the AMEDA task for both positions. The ankle AMEDA has five depths of ankle inversion. We compared muscle activity between the body positions, and muscle activity between inversion depths “1” and “5” (within each position). Lower-limb muscle tone and muscle stiffness were assessed at rest in both body positions using the MyotonPRO. Results: Fifty-five participants between the ages of 18 and 65 (28 females, 27 males; mean age of 40 years) completed the study. The AMEDA scores, muscle tone and stiffness were reduced when the participants were on the lunar wedge bed, compared to upright standing (p = 0.002; p < 0.001; p < 0.001). Some lower-limb muscles exhibited less activity in the lunar wedge-bed position compared to upright standing (tibialis anterior, peroneus longus, vastus lateralis, rectus femoris; p < 0.05) but others were unchanged (gastrocnemius, vastus medialis; p > 0.05). Muscle activity was unchanged between the AMEDA depths (p = 0.188). Conclusions: The results provide insight into how the somatosensory and neuromuscular systems respond to reduced weight bearing and potentially lunar gravity conditions, thereby informing how to target interventions for future missions. Full article

Background/Objectives: Ultrasound (US) imaging and echotexture analysis are emerging techniques for assessing muscle tissue quality in the post-stroke population. Clinical studies suggest that echovariation (EV) and echointensity (EI) serve as objective indicators of muscle impairment, although methodological limitations hinder their clinical translation. This secondary analysis aimed to refine the assessment of echotexture by using robust statistical techniques. Methods: A total of 130 regions of interest (ROIs) extracted from the gastrocnemius medialis of 22 post-stroke individuals were analyzed. First, inter-examiner reliability between two physiotherapists was assessed by using Cohen’s kappa for muscle impairment classification (low/high) for each echotexture feature. For each examiner, the correlation between the classification of the degree of impairment and the modified Heckmatt scale for each feature was analyzed. The dataset was then reduced to 44 ROIs (one image per leg per patient) and assessed by three physiotherapists to analyze inter-examiner reliability by using Light´s kappa and correlation between both assessment methods globally. Statistical differences in 21 echotexture features were evaluated according to the degree of muscle impairment. A binary logistic regression model was developed by using features with a Cohen’s kappa value greater than 0.9 as predictors. Results: A strong and significant degree of agreement was observed among the three examiners regarding the degree of muscle impairment (Kappa_light = 0.85, p < 0.001), with nine of the 21 features showing excellent inter-examiner reliability. The correlation between muscle impairment classification with the modified Heckmatt scale was very high and significant both globally and for each echotexture feature. Significant differences (<0.05) were found for EV, EI, dissimilarity, energy, contrast, maximum likelihood, skewness, and the modified Heckmatt scale. Logistic regression highlighted dissimilarity, entropy, EV, Gray-Level Uniformity (GLU), and EI as the main predictors of muscle tissue impairment. The EV and EI models showed high explanatory power (Nagelkerke’s pseudo-R² = 0.74 and 0.76) and robust classification performance (AUC = 94.20% and 95.45%). Conclusions: This secondary analysis confirms echotexture analysis as a reliable tool for post-stroke muscle assessment, validating EV and EI as key indicators while identifying dissimilarity, entropy, and GLU as additional relevant features. Full article

Background: Exoskeleton robots are emerging as a transformative technology in healthcare, rehabilitation, and industrial settings, providing significant benefits such as improving gait restoration and preventing injuries. These robots enhance mobility for individuals with neuromuscular disorders by providing muscular assistance and reducing physical strain, while also supporting workers in physically demanding tasks. They improve gait efficiency, muscle activation, and overall physical function, contributing to both rehabilitation and occupational health. Objective: This study aims to investigate the impact of exoskeleton use on muscle activation patterns, fatigue levels, and gait parameters in healthy individuals. Methods: Thirty-six participants engaged in a randomized sequence gait experiment on a treadmill for 30 min, both with and without an exoskeleton, with electromyography (EMG) and OptoGait measurements collected during the sessions. A one-week washout period was implemented before participants switched conditions. Results: In the Maximum voluntary contraction (MVC) analysis, significant differences were observed in the Rectus femoris (RF) and gastrocnemius(GM) when wearing the exoskeleton robot compared to not wearing it. At 10 min, 20 min, and 30 min, the differences were statistically significant (p < 0.05) for all muscles. In the muscle fatigue analysis, significant differences were observed in RF, GM, vastus medialis (VM), and hamstring(HS) at 10 min, 20 min, and 30 min (p < 0.05). In the step length and stride length analysis, significant differences were observed at 10 min and 30 min, but no differences were found at 20 min (p < 0.05). Conclusions: This study demonstrates that the use of the exoskeleton robot significantly impacts muscle activation, muscle fatigue, and gait parameters. The results emphasize the potential benefits of exoskeletons in enhancing mobility and reducing muscle strain, providing important insights for rehabilitation and occupational applications Full article

The ‘forward lunge’ is a crucial movement in badminton that demands effective muscle activation and coordination. This study compared the muscle activation patterns of professional and amateur male badminton players during this movement. A total of 24 players (12 professionals and 12 amateurs) participated, with surface electromyography (sEMG) used to measure the activity of 12 muscles on the right side during the lunge. The movement was divided into swing and support phases based on ground reaction force data. The sEMG signals were analyzed using integral EMG (iEMG) and root-mean-square (RMS) amplitude, and muscle synergy patterns were extracted via non-negative matrix factorization (NNMF) and k-means clustering. The results showed significantly higher iEMG and RMS values in muscles such as the gastrocnemius, biceps femoris, gluteus maximus, external oblique, and latissimus dorsi in professional players (p < 0.05), while no significant differences were observed in the tibialis anterior, vastus medialis, vastus lateralis, deltoideus, biceps, and soleus muscles. Muscle synergy analysis revealed three activation patterns in the professional group, compared to two in the amateur group. The additional synergy pattern in the professional players involved greater recruitment of lower limb and core muscles, especially during the support phase. In contrast, the amateur group showed earlier muscle activation but exhibited less efficient coordination. These findings suggest that muscle activation and coordination patterns in the forward lunge are influenced by playing level, highlighting the importance of lower limb and core training for badminton athletes to optimize performance and reduce injury risk. Full article

Mental imagery influences the body, movement, and technical skills of the dancer. The aim of this study was to identify the influence of dance imagery on the electromyographic parameters of selected muscles in a professional ballet dancer during three ballet tasks: parallel position, demi pointe relevé, and demi plié. Five mental imageries according to the Franklin Method^® were used: foot dome, the wheelbarrow, pushing the toes, space behind the kneecap, and the kneecap float. Electromyographic signals were recorded bilaterally for lumbar erector spinae, rectus abdominis, vastus medialis, long head of biceps femoris, lateral head of gastrocnemius, tibialis anterior, and fibularis longus. All of the mental imageries resulted in increased activity (above 20% compared with no-imagery performance) of the selected muscles in the studied classical dance positions and tasks. Overall, the ankle muscles were influenced the most. This study indicates that mental images effectively influence a physiological parameter, as indicated by an electromyographic signal. Full article

Background: Achilles tendon rupture rehabilitation protocols often emphasize two key factors, namely plantar flexion and load restriction during the early recovery stages. However, we hypothesize that variations in walking speed also play a significant role in affecting the load on the Achilles tendon. This study aims to explore the combined impact of plantar flexion angle and walking speed on the surface electromyography (EMG) activity of the calf muscles. Methods: Surface EMG measurements on 24 healthy volunteers assessed the activity of the calf muscles (gastrocnemius lateralis, gastrocnemius medialis, and soleus). Participants walked on a treadmill using two designs of ankle foot orthoses set at three different angles of the ankle joint (mainly 0°, 15°, or 30° plantar flexion), as well as barefoot and in sports shoes. The tests were performed at full loads of 1, 2 and 4 km/h or with additional measurements at 1 and 2 km/h with a partial load of 20 kg. The walking speed of 4 km/h in sports shoes was used as reference, corresponding to the maximum load on the calf muscles during walking. Results: Both orthoses demonstrated a significant reduction in EMG activity by more than half even at a 0° setting and 1 km/h compared to walking barefoot or in sports shoes. However, as walking speed increased to 2 km/h and especially to 4 km/h, EMG activity significantly increased, approaching the level of walking with sports shoes at 1 km/h. The results indicated that even minor changes in walking speed had a significant impact on muscle activity, underscoring the importance of this parameter. Conclusions: This study suggests that walking speed should be considered a crucial factor in rehabilitation protocols for Achilles tendon ruptures, alongside plantar flexion and load restrictions, to optimize recovery outcomes. Full article

Examining the dynamic interplay of muscle contributions to postural stability enhances our understanding of the neuromuscular mechanisms underlying balance control. This study examined the similarity in shape (using cross-correlation analysis) between seven individual lower limb electromyographic (EMG) signals and center-of-pressure (COP) displacements (i.e., EMG–COP correlation) in 20 young adults (25.2 ± 4.0 years) performing bipedal balance tasks on both stable and multi-axially unstable surfaces, testing the effects of four factors—leg dominance, surface stability, sway direction, and foot position—on individual EMG–COP correlations. The results revealed significant effects of leg dominance (p = 0.004), surface stability (p ≤ 0.001), and sway direction (p ≤ 0.001) on specific muscles. Notably, balancing on the non-dominant leg resulted in a stronger correlation between tibialis anterior activity and postural sway compared to the dominant leg. On a stable surface, postural sway showed stronger correlations with the rectus femoris, semitendinosus, biceps femoris, gastrocnemius medialis, and soleus muscles than on an unstable surface. Additionally, anteroposterior postural sway exhibited a greater correlation with semitendinosus and tibialis anterior activity compared to mediolateral sway. These findings underscore the importance of specific muscles in maintaining bipedal balance, with implications for improving balance performance across various populations. Full article

Objective: This study aimed to investigate the effects of a 12-week self-designed exercise game intervention on the kinematic and kinetic data of the supporting leg in preschool children during the single-leg jump. Methods: Thirty 5- to 6-year-old preschool children were randomly divided into an experimental group (EG) and a control group (CG). The BTS SMART DX motion capture analysis system was used to collect single-leg jump data before the intervention. The experimental group underwent a 12-week intervention, with self-designed exercise games conducted three times a week for 30 min each session, while the control group only participated in regular kindergarten recess activities and physical education classes. After the intervention, the same equipment was used to collect single-leg jump data again, and the kinematic and kinetic data were analyzed using Anybody 7.4 simulation software. Results: After the intervention, the experimental group showed significant changes in joint angles and joint torques, with a notable increase in the force exerted by dominant muscles such as the vastus medialis, vastus lateralis, and gastrocnemius and a significant increase in the ground reaction force. Although the control group also showed some changes in the dominant muscles, the changes were not as significant as those in the experimental group. Conclusions: A 12-week exercise game intervention significantly improved the technique and force characteristics of 5- to 6-year-old preschool children during the single-leg jump, making muscle exertion more focused and efficient and effectively enhancing explosive power and performance during the single-leg jump. Full article

Arm swing is an inherent aspect of human locomotion that enhances lower limb (LL) muscle activation, which may explain its benefits for stroke rehabilitation over fixed-arm approaches. This study analyzed how restricting arm movement affects LL muscle coordination by comparing treadmill walking with arms (WWA) and walking with no arms (WNA) through muscle synergy analysis. Surface electromyography was recorded from eight LL muscles in ten healthy participants. Significant differences were found in muscle activity envelopes at 50% of the gait cycle (GC) for the Gluteus Medius, 0% and 100% GC for the Vastus Lateralis and Semitendinosus, and 25% GC for the Semitendinosus, Gastrocnemius Medialis, and Soleus. The Rectus Femoris and Vastus Lateralis showed higher variability and activation in WNA compared to WWA. Synergy analysis revealed four muscle synergies, with a median global variance of 95%. While spatial components were similar, temporal differences emerged at 0% GC for Synergy 1, 5% and 90% GC for Synergy 2, and 95% GC for Synergy 3 (p < 0.05). Our results suggest that arm swing influences LL muscle activity and coordination during walking. Future studies will aim at understanding the effects of arm swing in stroke rehabilitation, which could help design more effective gait rehabilitation protocols including arm swing. Full article

Background/Objectives: Strokes remain a major global health concern, contributing significantly to disability and healthcare costs. Currently, there are no established indicators to accurately assess the degree of muscle tissue impairment in stroke-affected individuals. However, ultrasound imaging with an echotexture analysis shows potential as a quantitative tool to assess muscle tissue quality. This study aimed to identify specific echotexture features in the gastrocnemius medialis that effectively characterize muscle impairment in post-stroke individuals. Methods: An observational study was conducted with 22 post-stroke individuals. A total of 21 echotexture features were extracted and analyzed, including first-order metrics, a grey-level co-occurrence matrix, and a grey-level run length matrix. The modified Heckmatt scale was also applied to correlate with the most informative echotexture features. Results: Among the features analyzed, echovariation (EV), echointensity, and kurtosis emerged as the most informative indicators of muscle tissue quality. The EV was highlighted as the primary feature due to its strong and significant correlation with the modified Heckmatt scale (r = −0.81, p < 0.001) and its clinical and technical robustness. Lower EV values were associated with poorer muscle tissue quality, while higher values indicated better quality. Conclusions: The EV may be used as a quantitative indicator for characterizing the gastrocnemius medialis muscle tissue quality in post-stroke individuals, offering a more nuanced assessment than traditional qualitative scales. Future studies should investigate the correlation between the EV and other clinical outcomes and explore its potential to monitor the treatment efficacy, enhancing its applicability in clinical practice. Full article

Skeletal muscle fiber characteristics are pivotal in assessing meat quality. However, there is currently a lack of research precisely quantifying the total number of myofibers (TNM) of skeletal muscles. This study used Arbor Acres (AA) broilers and Wenchang (WC) chickens to determine the TNM of several skeletal muscles and the meat quality of the pectoralis major muscle (PM). The results showed that the TNMs of the PM in AA males and females were 935,363.64 ± 92,529.28 and 873,983.72 ± 84,511.28, respectively, significantly higher than those in WC (511,468.97 ± 73,460.81 and 475,371.93 ± 70,187.83) at 7 days of age (p < 0.01). In terms of gastrocnemius medialis in AA males and females, we recorded values of 207,551.43 ± 31,639.97 and 177,203.23 ± 28,764.01, showing a significant difference compared to the values observed in WC (146,313.03 ± 29,633.21 and 124,238.9 ± 20,136.95) (p < 0.01). Similarly, the levels of gastrocnemius lateralis exhibited a significant difference between AA and WC (p < 0.01). Furthermore, the essential, umami, and sweet amino acids were found to be significantly higher in WC compared to AA (p < 0.01). These findings offer valuable data and insights for accurately quantifying the TNM in livestock and for the development of further genetic breeding strategies for meat quality. Full article

This cross-sectional study examined gastrocnemius medialis fascicle length (FL) and anatomical cross-sectional area (ACSA) in female volleyball athletes aged 8–18 years, in an attempt to investigate morphological growth changes during childhood and adolescence. Methods: Eighty-nine athletes were assigned to five groups: 8–10, 10–12, 12–14, 14–16 and 16–18 years old. Height, body mass, leg and calf length were measured, and maturity offset was calculated from anthropometrics. FL and ACSA were assessed using ultrasonography. Results: FL was longer and ACSA was larger in the 12–14 y group compared with the 8–10 y group (4.31 ± 0.60 vs. 3.66 ± 0.40 cm, p = 0.008 and 13.08 ± 3.01 cm² vs. 9.98 ± 2.07 cm², p = 0.018, respectively). However, there were no differences in FL or ACSA among the groups aged between 12 and 18 years (p > 0.573 and p > 0.352). Notably the percentage increase in ACSA between the youngest (8–10 y) and the oldest group (16–18 y) was twofold greater than the percentage increase in FL (49% vs. 24%). Significant correlations were found between anthropometric characteristics FL and ACSA (r = 0.366–760, p < 0.001). Conclusions: These data indicate that there is a rapid increase in FL and ACSA from the age of 8 y until the age of 14 y, which is a crucial time frame for muscle growth. Full article