Muscle Activation Patterns Research Articles

Stride-to-stride fluctuations and temporal patterns of muscle activity exhibit similar responses during walking to variable visual cues

Incorporating variability within gait retraining approaches has been proposed and shown to lead to positive changes. Specifically, submitting the individuals to walk in synchrony to cues that are temporally organized with a fractal-like patterns, promotes changes at the stride-to-stride fluctuations closer to those typically find in young adults. However, there is still a need to understand the underlying neuromuscular mechanisms associated to such improvement. Thus, this study aimed to investigate whether changes in the temporal structure of the variability in gait patterns are accompanied by changes in muscle activity patterns. Fourteen young individuals walked synchronized to one uncued (UNC) and three cued conditions: isochronous (ISO), fractal (FRC) and random (RND). Inter-stride intervals were determined from an accelerometer placed on the lateral malleoli. Inter-muscle peak intervals were obtained from the electromyographic signal from the gastrocnemius muscle. Fractal scaling, obtained through detrended fluctuation analysis, and coefficient of variation were calculated. Repeated measures ANOVAs were used to identify differences between conditions. Significant main effect was observed for both fractal scaling and coefficient of variation. Both shown no differences between UNC and FRC conditions, while ISO and RND were significantly lower compared to UNC and FRC conditions. In addition, a Pearson’s Correlation was used to test the correlation between variables. A strong correlation was found the temporal structure of gait and muscle activity patterns. These findings strengthen the current literature regarding the incorporation of variability within cued approaches. Specifically, it shows that such an approach allows the modification of the neuromuscular processes underlying the stride-to-stride fluctuations.

Static versus dynamic muscle modelling in extinct species: a biomechanical case study of the Australopithecus afarensis pelvis and lower extremity.

The force a muscle generates is dependent on muscle structure, in which fibre length, pennation angle and tendon slack length all influence force production. Muscles are not preserved in the fossil record and these parameters must be estimated when constructing a musculoskeletal model. Here, we test the capability of digitally reconstructed muscles of the Australopithecus afarensis model (specimen AL 288-1) to maintain an upright, single-support limb posture. Our aim was to ascertain the influence that different architectural estimation methods have on muscle specialisation and on the subsequent inferences that can be extrapolated about limb function. Parameters were estimated for 36 muscles in the pelvis and lower limb and seven different musculoskeletal models of AL 288-1 were produced. These parameters represented either a 'static' Hill-type muscle model (n=4 variants) which only incorporated force, or instead a 'dynamic' Hill-type muscle model with an elastic tendon and fibres that could vary force-length-velocity properties (n=3 variants). Each muscle's fibre length, pennation angle, tendon slack length and maximal isometric force were calculated based upon different input variables. Static (inverse) simulations were computed in which the vertical and mediolateral ground reaction forces (GRF) were incrementally increased until limb collapse (simulation failure). All AL 288-1 variants produced somewhat similar simulated muscle activation patterns, but the maximum vertical GRF that could be exerted on a single limb was not consistent between models. Three of the four static-muscle models were unable to support >1.8 times body weight and produced models that under-performed. The dynamic-muscle models were stronger. Comparative results with a human model imply that similar muscle group activations between species are needed to sustain single-limb support at maximally applied GRFs in terms of the simplified static simulations (e.g., same walking pose) used here. This approach demonstrated the range of outputs that can be generated for a model of an extinct individual. Despite mostly comparable outputs, the models diverged mostly in terms of strength.

Muscular Strategies for Correcting the Pelvic Position to Improve Posture-An Exploratory Study.

The correction of postural weaknesses through the better positioning of the pelvis is an important approach in sports therapy and physiotherapy. The pelvic position in the sagittal plane is largely dependent on the muscular balance of the ventral and dorsal muscle groups. The aim of this exploratory study was to examine whether healthy persons use similar muscular activation patterns to correct their pelvic position or whether there are different motor strategies. The following muscles were recorded in 41 persons using surface electromyography (EMG): M. trapezius pars ascendens, M. erector spinae pars lumbalis, M. gluteus maximus, M. biceps femoris, M. rectus abdominis, and M. obliquus externus. The participants performed 10 voluntary pelvic movements (retroversion of the pelvis). The anterior pelvic tilt was measured videographically via marker points on the anterior and posterior superior iliac spine. The EMG data were further processed and normalized to the maximum voluntary contraction. A linear regression analysis was conducted to assess the relationship between changes in the pelvic tilt and muscle activities. Subsequently, a Ward clustering analysis was applied to detect potential muscle activation patterns. The differences between the clusters and the pelvic tilt were examined using ANOVA. Cluster analysis revealed the presence of four clusters with different muscle activation patterns in which the abdominal muscles and dorsal muscle groups were differently involved. However, the gluteus maximus muscle was involved in every activation pattern. It also had the strongest correlation with the changes in pelvic tilt. Different individual muscle patterns are used by different persons to correct pelvic posture, with the gluteus maximus muscle apparently playing the most important role. This can be important for therapy, as different muscle strategies should be trained depending on the individually preferred motor patterns.

How to activate the glutes best? Peak muscle activity of acceleration-specific pre-activation and traditional strength training exercises.

Isometric training and pre-activation are proven to enhance acceleration performance. However, traditional strength training exercises do not mirror the acceleration-specific activation patterns of the gluteal muscles, characterized by ipsilateral hip extension during contralateral hip flexion. Therefore, the aim of the study was to determine gluteal muscle activity of acceleration-specific exercises compared to traditional strength training exercises. In a cross-sectional study design, thepeak electromyographic activity of two acceleration-specific exercises was investigated and compared to two traditional strength training exercises each for the gluteus maximus and medius. Twenty-four participants from various athletic backgrounds (13 males, 11 females, 26years, 178cm, 77kg) performed four gluteus maximus [half-kneeling glute squeeze (HKGS), resisted knee split (RKS), hip thrust (HT), split squat (SS)] and four gluteus medius [resisted prone hip abduction (RPHA), isometric clam (IC), side-plank with leg abduction (SP), resisted side-stepping (RSS)] exercises in a randomized order. The RKS (p = 0.011, d = 0.96) and the HKGS (p = 0.064, d = 0.68) elicited higher peak gluteus maximusactivity than the SS with large and moderate effects, respectively. No significant differences (p > 0.05) were found between the HT, RKS and HKGS.The RPHA elicited significantly higher gluteus medius activity with a large effect compared to RSS (p < 0.001, d = 1.41) and a moderate effect relative to the SP (p = 0.002, d = 0.78). The acceleration-specific exercises effectively activate the gluteal muscles for pre-activation and strength training purposes and might help improve horizontal accelerationdue to their direct coordinative transfer.

Treadmill induced belt-accelerations may not accurately evoke the muscle responses to obstacle trips in older people

BackgroundTreadmill belt-accelerations are a commonly utilised surrogate for tripping, but their physiological validity is unknown. This study examined if a treadmill belt-acceleration induces lower limb muscle activation responses similar to a trip on a walkway. Methods38 older people (65+ years) experienced one treadmill belt-acceleration and one walkway obstacle trip in random order. Muscle responses were assessed bilaterally using surface electromyography on the rectus femoris (RF), tibialis anterior (TA), semitendinosus (ST) and gastrocnemius medial head (GM). Unperturbed muscle activity, post-perturbation onset latency, peak magnitude, time to peak and co-contraction index (CCI) were examined. ResultsMuscle activity in the right ST was greater during unperturbed walking on the treadmill compared to walkway (P=0.011). Compared to a treadmill belt-acceleration, a walkway trip elicited faster onset latencies in all muscles; greater peak magnitudes in the left RF, TA, GM and right GM; faster time to peaks in the left TA and right GM; and lower knee and ankle muscle CCI (P<0.05). ConclusionsWalkway trips and treadmill belt-accelerations elicit distinct muscle activation patterns. While walkway trips induced faster and larger muscle responses, treadmill belt-accelerations involved greater co-contraction. Therefore, treadmill belt-accelerations may not accurately simulate the muscle responses to trips.

Forelimb muscle activation patterns in American alligators: Insights into the evolution of limb posture and powered flight in archosaurs.

The evolution of archosaurs provides an important context for understanding the mechanisms behind major functional transformations in vertebrates, such as shifts from sprawling to erect limb posture and the acquisition of powered flight. While comparative anatomy and ichnology of extinct archosaurs have offered insights into musculoskeletal and gait changes associated with locomotor transitions, reconstructing the evolution of motor control requires data from extant species. However, the scarcity of electromyography (EMG) data from the forelimb, especially of crocodylians, has hindered understanding of neuromuscular evolution in archosaurs. Here, we present EMG data for nine forelimb muscles from American alligators during terrestrial locomotion. Our aim was to investigate the modulation of motor control across different limb postures and examine variations in motor control across phylogeny and locomotor modes. Among the nine muscles examined, m. pectoralis, the largest forelimb muscle and primary shoulder adductor, exhibited significantly smaller mean EMG amplitudes for steps in which the shoulder was more adducted (i.e., upright). This suggests that using a more adducted limb posture helps to reduce forelimb muscle force and work during stance. As larger alligators use a more adducted shoulder and hip posture, the sprawling to erect postural transition that occurred in the Triassic could be either the cause or consequence of the evolution of larger body size in archosaurs. Comparisons of EMG burst phases among tetrapods revealed that a bird and turtle, which have experienced major musculoskeletal transformations, displayed distinctive burst phases in comparison to those from an alligator and lizard. These results support the notion that major shifts in body plan and locomotor modes among sauropsid lineages were associated with significant changes in muscle activation patterns.

The effect of bolus properties on muscle activation patterns and TMJ loading during unilateral chewing

Mastication is a vital human function and uses an intricate coordination of muscle activation to break down food. Collection of detailed muscle activation patterns is complex and commonly only masseter and anterior temporalis muscle activation are recorded. Chewing is the orofacial task with the highest muscle forces, potentially leading to high temporomandibular joint (TMJ) loading. Increased TMJ loading is often associated with the onset and progression of temporomandibular disorders (TMD). Hence, studying TMJ mechanical stress during mastication is a central task. Current TMD self-management guidelines suggest eating small and soft pieces of food, but patient safety concerns inhibit in vivo investigations of TMJ biomechanics and currently no in silico model of muscle recruitment and TMJ biomechanics during chewing exists. For this purpose, we have developed a state-of-the-art in silico model, combining rigid body bones, finite element TMJ discs and line actuator muscles. To solve the problems regarding muscle activation measurement, we used a forward dynamics tracking approach, optimizing muscle activations driven by mandibular motion. We include a total of 256 different combinations of food bolus size, stiffness and position in our study and report kinematics, muscle activation patterns and TMJ disc von Mises stress. Computed mandibular kinematics agree well with previous measurements. The computed muscle activation pattern stayed stable over all simulations, with changes to the magnitude relative to stiffness and size of the bolus. Our biomedical simulation results agree with the clinical guidelines regarding bolus modifications as smaller and softer food boluses lead to less TMJ loading. The computed mechanical stress results help to strengthen the confidence in TMD self-management recommendations of eating soft and small pieces of food to reduce TMJ pain.

Masticatory Muscles Activation and TMJ Space During Asymmetrically Loaded Jaw Closing

Masticatory muscle activation and temporomandibular joint (TMJ) load generated during asymmetrically loaded jaw closing are largely unknown. Two different strategies were developed to explain how the central nervous system (CNS) generates muscle activation patterns during motion: minimization of joint load (MJL) vs. minimization of muscle effort (MME). The aim of the present study was to investigate, experimentally, the neuromuscular strategy selected by the CNS to coordinate jaw closing in reaction to the application of an external asymmetric load. Masticatory muscle activation was measured with electromyography (EMG) and the minimum intra-articular distance (MID) was assessed by dynamic stereometry to infer joint loading. Ten healthy subjects performed jaw-closing movements against an asymmetric mandibular load set from 0.0 to 2.0 kg in 0.5-kg steps. Recordings were analyzed by exploratory and graphical statistical tools. Moreover, the observed differences in MID and EMG among the various mandibular loads were tested using non-parametric tests for repeated measures data. The ipsilateral-contralateral differences in MID and EMG of the anterior temporalis showed a significant increase (p < 0.001, p = 0.01) with increasing asymmetrical load with both joints being most heavily loaded at 1 kg. EMG signals of the masseter did not change significantly with increasing load. This study is the first to have analyzed the changes in the TMJ intra-articular space during asymmetrically loaded jaw-closing movements, not only three dimensionally and dynamically, but also combined with EMG. Asymmetrical load affected the TMJ space and masticatory muscle activation patterns, primarily resulting in an increased activation of the anterior temporalis muscle. This might suggest the involvement of a control mechanism to protect the joints from overloading. However, the results do not fully support the hypothesis of MJL nor the MME strategy.

Sensorimotor adaptation of locomotor synergies to gravitational constraint

This study investigates the impact of gravity on lower limb muscle coordination during pedaling. It explores how pedaling behaviors, kinematics, and muscle activation patterns dynamically adapts to changes in gravity and resistance levels. The experiment was conducted in parabolic flights, simulating microgravity, hypergravity (1.8 g), and normogravity conditions. Participants pedaled on an ergometer with varying resistances. The goal was to identify potential changes in muscle synergies and activation strategies under different gravitational contexts. Results indicate that pedaling cadence adjusted naturally in response to both gravity and resistance changes. Cadence increased with higher gravity and decreased with higher resistance levels. Muscular activities were characterized by two synergies representing pull and push phases of pedaling. The timing of synergy activation was influenced by gravity, with a delay in activation observed in microgravity compared to other conditions. Despite these changes, the velocity profile of pedaling remained stable across gravity conditions. The findings strongly suggest that the CNS dynamically manages the shift in body weight by finely tuning muscular coordination, thereby ensuring the maintenance of a stable motor output. Furthermore, electromyography analysis suggest that neuromuscular discharge frequencies were not affected by gravity changes. This implies that the types of muscle fibers recruited during exercise in modified gravity are similar to those used in normogravity. This research has contributed to a better understanding of how the human locomotor system responds to varying gravitational conditions, shedding light on the potential mechanisms underlying astronauts’ gait changes upon returning from space missions.

Development and validation of a novel ankle joint musculoskeletal model.

An improved understanding of contact mechanics in the ankle joint is paramount for implant design and ankle disorder treatment. However, existing models generally simplify the ankle joint as a revolute joint that cannot predict contact characteristics. The current study aimed to develop a novel musculoskeletal ankle joint model that can predict contact in the ankle joint, together with muscle and joint reaction forces. We modelled the ankle joint as a multi-axial joint and simulated contact mechanics between the tibia, fibula and talus bones in OpenSim. The developed model was validated with results from experimental studies through passive stiffness and contact. Through this, we found a similar ankle moment-rotation relationship and contact pattern between our study and experimental studies. Next, the musculoskeletal ankle joint model was incorporated into a lower body model to simulate gait. The ankle joint contact characteristics, kinematics, and muscle forces were predicted and compared to the literature. Our results revealed a comparable peak contact force and the same muscle activation patterns in four major muscles. Good agreement was also found in ankle dorsi/plantar-flexion and inversion/eversion. Thus, the developed model was able to accurately model the ankle joint and can be used to predict contact characteristics in gait.

Teres minor deficiency does not predict clinically inferior external rotation after reverse total shoulder arthroplasty: a 2-year matched cohort study

BackgroundCurrent teaching maintains that reverse total shoulder arthroplasty (RTSA) is unlikely to restore external rotation (ER) without a functional posterior rotator cuff, specifically the teres minor (TM). This study compared restoration of ER in TM-deficient (TMD) with TM-intact (TMI) shoulders after RTSA. MethodsAll patients who underwent lateralized RTSA using an onlay prosthesis with no adjunct tendon transfers between January 2014 and July 2020 and with 2-year follow-up were identified. Preoperative imaging review identified patients with TMD, and propensity score matching was used to create a control group of equal size. TMD was divided into three subgroups: 1) atrophy; 2) fracture/malunion/nonunion (proximal humerus); and 3) endoprosthesis. Primary outcome measures were active ER range of motion (ROM) measured at the side, ΔER ROM from baseline, ER strength, and American Shoulder and Elbow Surgeons subscore question, “can you reach back of head.” ResultsThirty-nine patients with TMD shoulders (atrophy: n = 15; fracture n = 14; endoprosthesis: n = 10) were matched with 39 patients with TMI shoulders. Although TMD was associated with reduced baseline ER ROM (13.6 vs. 28.8; P = .004), the TMD group achieved greater ΔER ROM 2 years after RTSA (24.6 vs. 10.3; P = .014) and demonstrated comparable 2-year ER ROM (38.6 vs. 40.7; P = .484). The TMD group had a higher rate of ER weakness (12% vs. 0%; P = .044) but no difference in ability to reach back of head (unable: 24% vs. 20%; P = .686) or patient-reported functional scores (2-year American Shoulder and Elbow Surgeons: 76.2 vs. 74.8; P = .793). ConclusionThis study suggests that patients with an insufficient or absent teres minor can achieve satisfactory ER ROM and function after lateralized RTSA similar to their TMI peers. Future study will seek to identify muscle activation patterns of the shoulder girdle that allow TMD patients to overcome this insufficiency to perform activities requiring ER.

Intermuscular coherence reveals that affective emotional pictures modulate neural control mechanisms during the initiation of arm pointing movements.

Several studies in psychology provided compelling evidence that emotions significantly impact motor control. Yet, these evidences mostly rely on behavioral investigations, whereas the underlying neurophysiological processes remain poorly understood. Using a classical paradigm in motor control, we tested the impact of affective pictures associated with positive, negative or neutral valence on the kinematics and patterns of muscle activations of arm pointing movements performed from a standing position. The hand reaction and movement times were measured and electromyography (EMG) was used to measure the activities from 10 arm, leg and trunk muscles that are involved in the postural maintenance and arm displacement in pointing movements. Intermuscular coherence (IMC) between pairs of muscles was computed to measure changes in patterns of muscle activations related to the emotional stimuli. The hand movement time increased when an emotional picture perceived as unpleasant was presented as compared to when the emotional picture was perceived as pleasant. When an unpleasant emotional picture was presented, beta (β, 15-35 Hz) and gamma (γ, 35-60 Hz) IMC decreased in the recorded pairs of postural muscles during the initiation of pointing movements. Moreover, a linear relationship between the magnitude of the intermuscular coherence in the pairs of posturo-focal muscles and the hand movement time was found in the unpleasant scenarios. These findings reveal that emotional stimuli can significantly affect the content of the motor command sent by the central nervous system to muscles when performing voluntary goal-directed movements.

Electromyography of paraspinal muscles during self-corrective positions in adolescent idiopathic scoliosis.

Self-corrective exercise is commonly used in the training protocol of patients with adolescent idiopathic scoliosis (AIS). The muscle activation pattern during symmetrical and overcorrection exercises is then explored to guide the treatment. To compare the paraspinal muscle activity during three self-corrective positions and the habitual standing in AIS. Thirty-three adolescents with double curved scoliosis were examined. The curve type and Cobb's angle were determined from their whole spine X-ray. They adopted habitual standing, symmetrical correction and two overcorrected positions (O1 and O2). The surface electromyography (EMG) was monitored on both sides of paraspinal muscles at the apex areas of scoliotic curves. The EMG ratio between sides was inferred as the corrective effect. All three self-correction positions produced greater EMG ratios compared with the habitual standing. The greatest EMG ratios were observed during the O1 position at the thoracic curve and the habitual standing at the lumbar curve. Participants with different subtypes of curves exhibited similar patterns of EMG ratios. From the biomechanical viewpoint, all three self-corrective positions possibly provided therapeutic effects for the scoliotic body regardless of the subtype of scoliosis curves. The O1 position seemed to be most effective for the adjusting activation of thoracic paraspinal muscles. The symmetrical corrective position is otherwise recommended for adjusting the lumbar muscle activation.

A new methodological approach to characterize selective motor control in children with cerebral palsy.

Despite being a primary impairment in individuals with cerebral palsy (CP), selective motor control (SMC) is not routinely measured. Personalized treatment approaches in CP will be unattainable without the ability to precisely characterize the types and degrees of impairments in motor control. The objective of this study is to report the development and feasibility of a new methodological approach measuring muscle activation patterns during single-joint tasks to characterize obligatory muscle co-activation patterns that may underly impaired SMC. Muscle activation patterns were recorded during sub-maximal voluntary isometric contraction (sub-MVIC) tasks at the hip, knee, and ankle with an interactive feedback game to standardize effort across participants. We calculated indices of co-activation, synergistic movement, mirror movement, and overflow (indices range 0-2, greater scores equal to greater impairment in SMC) for each isolated joint task in 15 children - 8 with typical development (TD) (mean age 4.7 ± 1.0 SD years) and 7 with CP (mean age 5.8 ± 0.7 SD years). Indices were compared with Mann-Whitney tests. The relationships between the indices and gross motor function (GMFM-66) were examined with Pearson's r. Mean indices were higher in the CP vs. the TD group for each of the six tasks, with mean differences ranging from 0.05 (abduction and plantarflexion) to 0.44 (dorsiflexion). There was great inter-subject variability in the CP group such that significant group differences were detected for knee flexion mirroring (p = 0.029), dorsiflexion coactivation (p = 0.021), and dorsiflexion overflow (p = 0.014). Significant negative linear relations to gross motor function were found in all four indices for knee extension (r = -0.56 to -0.75), three of the indices for ankle dorsiflexion (r = -0.68 to -0.78) and in two of the indices for knee flexion (r = -0.66 to -0.67), and ankle plantarflexion (r = -0.53 to -0.60). Indices of coactivation, mirror movement, synergy, and overflow during single-joint lower limb tasks may quantify the type and degree of impairment in SMC. Preliminary concurrent validity between several of the indices of SMC and gross motor function was observed. Our findings established the feasibility of a new methodological approach that quantifies muscle activation patterns using electromyography paired with biofeedback during single-joint movement.

Pushing forward: exploring the impact of the sitting position on muscle activation patterns and force generation during paralympic sit-cross-country skiing.

Paralympic cross-country sit-skiing is a discipline of the Paralympic Winter Games where athletes use a specialized sledge. Athletes are classified into different groups according to their functional abilities. The double poling technique is used to push the sledge forward and generate speed. Different sitting positions in the sledge are used based on the individual impairment. To date there is no data available on the effects of these different positions on muscle activation patterns. The aim of this study was to analyze the muscle activation patterns of the trunk and upper body muscles in relation to the poling force. Nine Able-bodied athletes were tested on a treadmill at submaximal speed in three sitting positions for 4 min in a flat and uphill condition. Sitting positions included a "knee-high" position, a "knee-low" position, and a "neutral" position with the sitting platform parallel to the ground. Unilateral pole forces and surface EMG from three trunk muscles, two upper limb muscles, and one lower limb muscle were recorded simultaneously on the dominate side. Data were segmented into individual cycles and mean values and standard deviations calculated for each subject and condition. Statistical analyses, including a Friedman test and Bonferroni correction, were applied to examine significant differences across different sitting positions. Our findings demonstrate that while certain muscle groups such as the erector spinae and triceps show consistent patterns of activation across different sitting positions, there is considerable variability among individual athletes, suggesting individualized strategies for task execution. Overall, force application was most efficient in the "knee low" position with 691.33 ± 148.83 N and least efficient in the "knee high" position with 582.81 ± 115.11 N. Testing impaired athletes will be the next step in understanding the neurophysiological aspects of the poling movement. This experimental protocol provides a basis for understanding the movement of paralympic cross-country sit-skiing in greater depth.

Effect of Corrective Exercises on Posture, Upper Extremity Muscle Activity, and Shoulder Kinematics in Male Handball Players With Upper Cross Syndrome

Background and Aims Abnormal posture and alterations in movement and muscle activity patterns have been reported in people with upper cross syndrome (UCS). These changes can lead to imbalance in muscle activation, altered movement patterns, and biomechanical changes. The present study aims to investigate the effect of corrective exercises on posture, upper extremity muscle activity, and shoulder kinematics in male handball players with UCS. Methods This quasi-experimental study was conducted on 30 male handball players with UCS who were randomly divided into exercise (n=15) and control (n=15) groups. The variables including upper extremity muscle activation patterns, shoulder kinematics, forward head posture, forward shoulder posture, and kyphosis were evaluated before and after intervention. Should kinematics and activation patterns of upper extremity muscles (supraspinatus, lumbar erector spinae, upper trapezius, middle trapezius, latissimus dorsi, pectoralis major) were recorded using electromyography and motion analyzer. The angles of forward head and forward shoulder were assessed using photographic method taken from lateral view, and Kyphosis angle was measured using a flexible ruler before and after exercises. The exercise group performed the comprehensive corrective exercises for 8 weeks (3 sessions per week), but the control group did not receive any intervention. To analyze the data, two-way analysis of variance and Bonferroni test were used. The significant level was set at 0.05. Results Forward head posture (P=0.001), forward shoulder posture (P=0.003), and kyphosis (P=0.002) showed significant improvements in the exercise group compared to the control group from pretest to post-test phase. In the preparatory and throw phases (slow and fast throwing), higher activities of supraspinatus, lumbar erector spinae, upper trapezius, middle trapezius, latissimus dorsi, and pectoralis major were observed in the exercise group compared to the control group (P=0.05). Moreover, in the preparatory and throw phases, higher range of motion of shoulder flexion, forward flexion of shoulder, internal rotation of shoulder, external rotation of shoulder, and shoulder abduction were observed in the exercise group compared to the control group (P=0.05). Conclusion Corrective exercises can significantly alter shoulder kinematics and upper extremity muscle activity patterns in male handball players with UCS, which can be used in future studies to prevent UCS in handball players during throwing the ball.

Kinetics, Kinematics, and Muscle Activity Patterns During Back Squat With Different Contributions of Elastic Resistance.

Performing back squats with elastic bands has been widely used in resistance training. Although research demonstrated greater training effects obtained from adding elastic bands to the back squat, little is known regarding the optimal elastic resistance and how it affects neuromuscular performance. This study aimed to compare the force, velocity, power, and muscle activity during back squats with different contributions of elastic resistance. Thirteen basketball players performed 3 repetitions of the back squat at 85% of 1-repetition maximum across 4 conditions: (1)total load from free weightand (2)20%, (3)30%, and (4)40% of the total load from elastic band and the remaining load from free weight. The eccentric and concentric phases of the back squat were divided into upper, middle, and bottom phases. In the eccentric phase, mean velocity progressively increased with increasing elastic resistance, and muscle activity of the vastus medialis and rectus femoris significantly increased with the largest elastic resistance in the upper phase (P ≤ .036). In the concentric phase, mean power (P ≤ .021) and rate of force development (P ≤ .002) significantly increased with increasing elastic resistance. Furthermore, muscle activity of the vastus lateralis and vastus medialis significantly improved with the largest elastic resistance in the upper phases (P ≤ .021). Velocity, power, rate of force development, and selective muscle activity increased as the elastic resistance increased in different phases during the back-squat exercise.

Precise sensors in detecting stress in workers in the industry: A review

Stress in the work environment has an impact on worker welfare and industrial productivity. This paper reviews the use of precision sensors in detecting workers’ physiological responses to stress in industry. The focus is on sensors that measure heart rate, sweat rate, body temperature, muscle activity and sleep patterns. The wearable sensor is the main highlight. Despite implementation challenges, precision sensors offer the potential for real-time monitoring to create healthier and more productive work environments.

Electromyographic Insights and Simulations of Core Training in Compression Tights: Implications for Performance and Wearable Ergonomic

In exploring the performance-enhancing effects of compression sportswear, this study investigates its impact on trunk muscle activation during core stability training, with a particular focus on the biomechanical implications of this relationship. This research posits the existence of an Equilibrium Point of Motion (EPM) and employs surface Electromyography (EMG) to measure muscular responses in the Erector Spinae (ES), External Oblique (EO), and Rectus Abdominis (RA) during exercises performed with and without compression wear. Results revealed that compression garments significantly augment root mean square (RMS) values for ES and EO muscles, suggesting differential muscle activation patterns. Further, the application of OpenSim modeling of full-body musculoskeletal mechanics facilitated a novel analysis of muscle forces and activations, enhancing the understanding of sportswear functionality in an ergonomic context. This approach uncovered significant correlations between actual and simulated muscle activations, particularly for the ES and EO during a gluteal bridge exercise. These insights contribute to the development of ergonomically-engineered sportswear aimed at optimizing athletic performance and provide a valuable reference for future sportswear design and research.

Ab. No. 170 Impact of Dynamic Postural Exercises on Electromyographic Activity, Co-Contraction and Joint Position Sense in Upper Cross Syndrome: A Pilot Study

Introduction: A greater prevalence with no strong rehabilitation program for Upper Crossed Syndrome (UCS) accompanied the purpose to find out the efficacy of dynamic postural exercise developed on the basis of identification of muscle activation pattern in UCS.This will help in effective management of patients suffering from UCS. Methods: 14 subjects with diagnosed UCS were randomly allocated to experimental and control groups (N=14; n=7). Participants were asked to perform 4 exercises (YTWL) using elastic resistance band during which amplitude of muscle activation and cocontraction ratio with Surface electrodes using 4 channel electromyographic system were measured.12 muscles of both side (Upper, middle and lower trapezius, serratus anterior, pectoralis major, anterior scalene) were assessed. The intervention of experimental group consisted of seven exercises. Both groups were given hot pack, TENS and cervical AROM exercises. The intervention was prescribed for three days a week for 8 weeks. Cervical kinesthesia was measured using joint position sense error (JPSE) test. All the outcome variables were recorded at the baseline and after 8 weeks. Result: Statistically significant difference (p≤0.05) of mean amplitude in pre-post values of experimental group as well as between group were found. Between group analysis of UT:LT, SC:AS contraction ratio and joint position sense also found to be significant(p≤0.05). Conclusion: There was a significant improvement in mean amplitude and cocontraction of cervicothoracic muscles in Dynamic Postural Exercise group. Kinesthesia also improved in experimental group. Implications: A focused rehabilitation program for UCS will help in improving the quality of life and functional efficacy.