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.

An open-source toolbox for enhancing the assessment of muscle activation patterns during cyclical movements.

Objective.The accurate temporal analysis of muscle activations is of great importance in several research areas spanning from the assessment of altered muscle activation patterns in orthopaedic and neurological patients to the monitoring of their motor rehabilitation. Several studies have highlighted the challenge of understanding and interpreting muscle activation patterns due to the high cycle-by-cycle variability of the sEMG data. This makes it difficult to interpret results and to use sEMG signals in clinical practice. To overcome this limitation, this study aims at presenting a toolbox to help scientists easily characterize and assess muscle activation patterns during cyclical movements.Approach.CIMAP(Clustering for the Identification of Muscle Activation Patterns) is an open-source Python toolbox based on agglomerative hierarchical clustering that aims at characterizing muscle activation patterns during cyclical movements by grouping movement cycles showing similar muscle activity.Main results.From muscle activation intervals to the graphical representation of the agglomerative hierarchical clustering dendrograms, the proposed toolbox offers a complete analysis framework for enabling the assessment of muscle activation patterns. The toolbox can be flexibly modified to comply with the necessities of the scientist.CIMAPis addressed to scientists of any programming skill level working in different research areas such as biomedical engineering, robotics, sports, clinics, biomechanics, and neuroscience. CIMAP is freely available on GitHub (https://github.com/Biolab-PoliTO/CIMAP).Significance.CIMAPtoolbox offers scientists a standardized method for analyzing muscle activation patterns during cyclical movements.

The Effects of High-Intensity, Short-Duration and Low-Intensity, Long-Duration Hamstrings Static Stretching on Contralateral Limb Performance.

INTRODUCTION: Increases in contralateral range of motion (ROM) have been shown following acute high-intensity and high-duration static stretching (SS) with no significant change in contralateral force, power, and muscle activation. There are currently no studies comparing the effects of a high-intensity, short-duration (HISD) or low-intensity, long-duration (LILD) SS on contralateral performance. PURPOSE: The aim of this study was to examine how HISD and LILD SS of the dominant leg hamstrings influence contralateral limb performance. METHODS: Sixteen trained participants (eight females, eight males) completed three SS interventions of the dominant leg hamstrings; (1) HISD (6 × 10 s at maximal point of discomfort), (2) LILD (6 × 30 s at initial point of discomfort), and (3) control. Dominant and non-dominant ROM, maximal voluntary isometric contraction (MVIC) forces, muscle activation (electromyography (EMG)), and unilateral CMJ and DJ heights were recorded pre-test and 1 min post-test. RESULTS: There were no significant contralateral ROM or performance changes. Following the HISD condition, the post-test ROM for the stretched leg (110.6 ± 12.6°) exceeded the pre-test (106.0 ± 9.0°) by a small magnitude effect of 4.2% (p = 0.008, d = 0.42). With LILD, the stretched leg post-test (112.2 ± 16.5°) exceeded (2.6%, p = 0.06, d = 0.18) the pre-test ROM (109.3 ± 16.2°) by a non-significant, trivial magnitude. There were large magnitude impairments, evidenced by main effects for testing time for force, instantaneous strength, and associated EMG. A significant ROM interaction (p = 0.02) showed that with LILD, the stretched leg significantly (p = 0.05) exceeded the contralateral leg by 13.4% post-test. CONCLUSIONS: The results showing no significant increase in contralateral ROM with either HISD or LILD SS, suggesting the interventions may not have been effective in promoting crossover effects.

Assessment of the Impact of Sensor-Based Ischemic Preconditioning with Different Cycling Periods on Upper Limb Strength in Bodybuilding Athletes.

Objective: This study designed experiments to explore the effects of ischemic preconditioning (IPC) intervention with different cycling periods on the upper limb strength performance of college male bodybuilding athletes. Methods: Ten bodybuilding athletes were recruited for a randomized, double-blind, crossover experimental study. All subjects first underwent pre-tests with two sets of exhaustive bench presses at 60% of their one-repetition maximum (1RM) to assess upper limb strength performance. They then experienced three different IPC intervention modes (T1: 1 × 5 min, T2: 2 × 5 min, T3: 3 × 5 min), as well as a non-IPC intervention mode (CON), followed by a retest of the bench press. An Enode pro device was used to record the barbell's velocity during the bench press movement (peak velocity (PV), mean velocity (MV)); power (peak power (PP), mean power (MP)); and time under tension (TUT) to evaluate upper limb strength performance. Results: PV values: T1 showed significant increases compared to pre-tests in the first (p = 0.02) and second (p = 0.024) tests, and were significantly greater than the CON (p = 0.032); T2 showed a significant increase in PV in the first test (p = 0.035), with no significant differences in other groups. MV values: T1 showed a significant increase in MV in the first test compared to the pre-test (p = 0.045), with no significant differences in other groups. PP values: T1 showed a highly significant increase in PP in the first test compared to the pre-test (p = 0.001), and was significantly higher than the CON (p = 0.025). MP values: T1 showed highly significant increases in MP in both the first (p = 0.004) and second (p = 0.003) tests compared to the pre-test; T2 showed a highly significant increase in MP in the first test (p = 0.039) and a significant increase in the second test (p = 0.039). T1's MP values were significantly higher than the CON in both tests; T2's MP values were significantly higher than the CON in the first (p = 0.005) and second (p = 0.024) tests. TUT values: T1 showed highly significant increases in TUT in the first (p < 0.001) and second (p = 0.002) tests compared to the pre-test, and were significantly higher than the CON. Conclusions: (1) Single-cycle and double-cycle IPC interventions both significantly enhance upper limb strength performance, significantly improving the speed and power in exhaustive bench press tests, with the single-cycle IPC intervention being more effective than the double-cycle IPC intervention. (2) The triple-cycle IPC intervention does not improve the upper limb strength performance of bodybuilding athletes in exhaustive bench presses.

Walking stress-induced changes in gait patterns and muscle activity: Patients with lumbar spinal stenosis versus asymptomatic controls.

INTRODUCTION: Patients with symptomatic lumbar spinal stenosis (sLSS) are often limited in their walking range because of worsening symptoms, which is thought to induce changes in the gait pattern. The aim of this study was to determine whether changes in gait pattern and muscle activity in these patients are elicited by a walking stress and differ from asymptomatic controls. METHODS: Twenty patients with sLSS and 19 asymptomatic controls performed a 30-minute walking stress. Gait was assessed using seven inertial sensors and sagittal joint range of motion (ROM) was calculated during different phases of gait. Muscle activation of the gluteus medius, erector spinae and multifidus muscles was measured by surface electromyography (EMG) and integrated EMGs (normalized to the maximum during gait) were calculated. Differences between groups and time points (beginning and end) were assessed using mixed factorial analysis of variance. RESULTS: Patients had less knee extension ROM in terminal stance, less knee flexion ROM in swing and less overall hip flexion/extension ROM than controls (p ≤ 0.03). There were no functionally relevant changes in these parameters during the walking stress. The integrated EMG was greater in all muscles in patients than in controls and increased in both groups during the walking stress in the paraspinal but not in the gluteus medius muscle. There was no interaction between group and time for any of the parameters. CONCLUSION: Differences in gait pattern and muscle activity between patients with sLSS and controls are generally present, but are not amplified by a walking stress.

Fascicle Behavior and Muscle Activity of The Biceps Femoris Long Head during Running at Increasing Speeds.

Hamstring strain injuries (HSIs) are prevalent in sports involving high-speed running and most of the HSIs are biceps femoris long head (BFlh) injuries. The primary cause for HSIs during high-speed running remains controversial due to the lack of in vivo measurement of the BFlh muscle behavior during running. Therefore, the purpose of this study was to quantify the muscle-tendon unit (MTU) and fascicle behavior of BFlh during running. Seven college male sprinters (22.14 ± 1.8 years; 177.7 ± 2.5 cm; 70.57 ± 5.1 kg; personal bests in 100m: 11.1 ± 0.2 s) were tested on a motorized treadmill instrumented with two force plate for running at 4, 5, 6m/s. The ground reaction force (GRF), 3D lower limb kinematics, EMG, and ultrasound images of biceps femoris long head (BFlh) in the middle region were recorded simultaneously. BFlh fascicles undergo little length change (about 1 cm) in the late swing phase during running at three submaximal speeds. BFlh fascicle lengthening accounted for about 30% of MTU length change during the late swing phase. BFlh was most active during the late swing and early stance phases, ranging from 83%MVC at a running speed of 4 m/s to 116%MVC at 6 m/s. Muscle fascicles in the middle region of BFlh undergo relatively little lengthening relative to the MTU in the late swing phase during running in comparison to results from simulation studies. These results suggest that there is a decoupling between the fascicle in the middle region and MTU length changes during the late swing phase of running.

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.

Acute neuromuscular and perceptual responses to blood flow restriction exercise in adults with severe haemophilia: A pilot study.

INTRODUCTION: No previous studies have implemented a standard blood flow restriction (BFR) training session in people with severe haemophilia (PwH), where this type of training has been contraindicated. AIMS: The purpose of this study was to evaluate the tolerability, adverse events, and neuromuscular and perceptual responses to an acute session of low load (LL) knee extensions with BFR in PwH under prophylaxis. METHODS: Eight PwH performed one LL-BFR session with 40% arterial occlusion pressure (AOP). Perceptual responses and adverse effects were assessed, together with high-density surface electromyography of vastus medialis (VM) and lateralis (VL). RESULTS: Significant normalized root mean square differences were found within each set, but not between sets. Spatial distribution (centroid displacement (p > .05), modified entropy (VM, set two, cycles three and five, p = .032) and coefficient of variation (VM, set two, cycles four and five lower than cycle three (p = .049; p = .036)) showed changes within each set. Median frequency showed a slight increase during cycle four of set four (p = .030). Rate of perceived exertion slightly increased with each set while tolerability slightly decreased in the last set and fear of training with BFR generally decreased after the session. CONCLUSIONS: In PwH, a LL-BFR session at 40% AOP is safe and feasible. Our results suggest that potential muscle impairments may blunt neuromuscular adaptations induced by BFR.

Enhancing lower limb and core muscle activation with blood flow restriction training: a randomized crossover study on high-intensity squat exercises.

Objective: The primary objective of this study was to assess the impact of high-intensity deep squat training integrated with various blood flow restriction (BFR) modalities on the activation of lower limb and core muscles. Methods: A randomized, self-controlled crossover experimental design was employed with 12 participants. The exercise protocol consisted of squat training at 75% of one-repetition maximum (1RM), performed in 3 sets of 8 repetitions with a 2-min inter-set rest period. This was conducted under four distinct BFR conditions: continuous low BFR (T1), intermittent medium BFR (T2), intermittent high BFR (T3), and a non-restricted control (C). Surface electromyography (EMG) was utilized to collect EMG signals from the target muscles during the BFR and squat training sessions. The root mean square (RMS) amplitude standard values were calculated for each squat set to quantify muscle activation levels, with these values expressed as a percentage of the maximum voluntary contraction (%MVC). Rating of Perceived Exertion was evaluated after each squat set, and leg circumference measurements were taken. Results: 1) During the first two sets of deep squats, the %MVC of the vastus lateralis and vastus medialis in all compression groups was significantly higher than that in the control group (p < 0.05). Furthermore, in the first set, the %MVC of the vastus lateralis in Group T3 was significantly higher than in Group T2 (p < 0.05). In the third set, the %MVC of the vastus medialis in Groups T1 and T3 was significantly lower than in the first two sets (p < 0.05). 2) Group T1 showed an increased activation of the biceps femoris and semitendinosus muscles in the second and third sets, with %MVC values significantly greater than in the first set (p < 0.05). Group T2 only showed an increase in biceps femoris activation in the third set (p < 0.05). Group T3 significantly increased the activation of the biceps femoris and semitendinosus muscles only in the first set (p < 0.05). 3) No significant differences were observed in the changes of rectus abdominis %MVC among the groups (p > 0.05). In the first set, Group T3's erector spinae %MVC was significantly higher than the control group's; in the second set, it was significantly higher than both Group T2 and the control group's (p < 0.05). 4) After training, a significant increase in thigh circumference was observed in all groups compared to before training (p < 0.05). 5) For RPE values, Group T2's post-squat values were significantly higher than the control group's after all three sets (p < 0.05). Group T1's RPE values were also significantly higher than the control group's after the third set (p < 0.05). Groups T1, T2, and C all had significantly higher RPE values in the second and third sets compared to the first set (p < 0.05). Conclusion: All BFR modalities significantly enhanced the activation level of the anterior thigh muscles, with the continuous low BFR mode demonstrating a more stable effect. No significant differences were found in the activation level of the rectus abdominis among the groups. However, the intermittent high BFR mode was the most effective in increasing the activation level of the erector spinae muscles. While BFR did not further augment leg circumference changes, it did elevate subjective fatigue levels. The RPE was lowest during squatting under the intermittent high BFR condition.

Analysing lower limb motion and muscle activation in athletes with ankle instability during dual-task drop-jump.

This study investigates the impact of chronic ankle instability (CAI) on athletes' lower extremity mechanics during bounce drop-jump landings with divided attention. Thirty Division I physical education voluntarily participated in the study. They performed two sets of bounce drop jumps: one set with a divided attention task and the other without. The obtained data were analysed using a paired t-test to compare the outcomes between the divided attention (DA) and non-divided attention (NDA) tasks. Athletes with CAI, during the DA task, displayed higher vertical landing forces, increased ankle inversion velocity, and greater range of motion of the ankle, knee, and hip in the frontal and transverse planes. They also exhibited insufficient neuromuscular preparation of the rectus femoris muscle. Notably, distinct kinematic alterations were observed in the ankle, knee, and hip joints regarding frontal and transverse lower-extremity kinematics. The findings suggest that athletes with CAI experience decreased activation of the rectus femoris muscle, which may impact their dynamic postural stability from pre-landing to ascending phases. Furthermore, the results indicate that individuals with CAI closely replicate the injury mechanisms encountered during a drop-jump landing task with divided attention. These insights offer valuable information about the real-time challenges faced by athletes with CAI.

The Disconnect Between Soccer Players' Perceived and Actual Electromyographic-Measured Muscle Activation.

Understanding muscle activation during exercises is crucial for devising effective training programs. We examined correlations between self-reported and electromyographic (EMG) muscle activity during upper-body exercises performed at loads corresponding to 4-6 repetition maximums (RMs). Thirteen male sub-elite soccer players who had previously engaged in resistance training participated in two testing sessions. In the initial session, the loads corresponding to 4-6 repetitions were determined for six exercises: Lat Pull Down (LPD), Barbell Bent Over Row (BBOR), Dumbbell Row (DR), Barbell Pull Over (BPO), Dumbbell Reverse Fly (DRF), and Dumbbell Concentration Curl (DCC). At post-exercise, participants rated their perceived muscle activation for three targeted muscles in each exercise on a 1-10 point Likert scale (LS). In the subsequent session, we used EMG to measure the activity of eight agonist and synergist muscles during these exercises. We found that one of two synergist muscles consistently demonstrated higher activity levels. Interestingly, we observed no difference in activity between primary and secondary (or synergist) muscles across all exercises. Most importantly, we found no significant correlation between the perceived muscle activation rate and the EMG measured activation level for any exercise. In conclusion, our findings suggest that, despite differential muscle activity during specific exercises, self-reported muscle activation may not accurately correspond to actual muscle activation, as measured via EMG, due to the participants' poor interoceptive awareness of muscles. These data highlight the potential limitations of relying on perceived muscle activation as a sole gauge of training intensity.

The effects of blood flow restriction training on post activation potentiation and upper limb muscle activation: a meta-analysis.

Objective: This meta-analysis aims to systematically evaluate the impact of blood flow restriction training (BFRT) on muscle activation and post-activation potentiation (PAP) in the upper limbs, to provide guidance for upper limb protocols aiming to enhance explosive strength and activation. Methods: PubMed, CNKI, Web of Science, and EBSCO databases were queried to identify randomized controlled trials (RCTs) investigating the effects of upper limb BFRT on muscle activation and PAP. Inclusion and exclusion criteria were applied using the Cochrane bias risk tool. Literature quality assessment and statistical analysis were conducted using Revman 5.4 and Stata 17.0 software. Sensitivity analysis and funnel plots were utilized to assess result stability and publication bias. Results: A total of 31 articles involving 484 participants were included in the analysis. Meta-analysis results showed that upper limb BFRT significantly increased muscle iEMG values [SMD = 0.89, 95%CI (0.21, 1.58), p = 0.01]. BFRT had a significant effect on upper limb explosive force [SMD = 0.73, 95%CI (0.41, 1.04), p < 0.00001]. Subgroup analysis based on literature heterogeneity (I 2 = 92%, 80%) showed that exhaustive BFRT significantly decreased upper limb iEMG [SMD = -0.67, 95%CI (-1.25, -0.09), p = 0.01], with exercise modes including maximum output power of bench press [SMD = 1.87, 95%CI (0.22, 3.53), p < 0.0001], exercise intensity of 40%-70% 1RM [SMD = 1.31, 95%CI (0.61, 2.01), p < 0.0001], and pressure intensity of ≥60% AOP [SMD = 0.83, 95%CI (0.43, 1.23), p < 0.0001] reaching maximum effects and statistical significance. Conclusion: Upper limb BFRT can induce muscle activation and PAP. BFRT with 40%-70% 1RM and ≥60% AOP in the upper limbs is more likely to promote PAP. Systematic Review Registration: http://inplasy.com, identifier INPLASY202430008.

Simulation of FES on the forearm with muscle-specific activation resolution.

Introduction: Functional electrical stimulation (FES) is an established method of supporting neurological rehabilitation. However, particularly on the forearm, it still cannot elicit selective muscle activations that form the basis of complex hand movements. Current research approaches in the context of selective muscle activation often attempt to enable targeted stimulation by increasing the number of electrodes and combining them in electrode arrays. In order to determine the best stimulation positions and settings, manual or semi-automated algorithms are used. This approach is limited due to experimental limitations. The supportive use of simulation studies is well-established, but existing simulation models are not suitable for analyses of selective muscle activation due to missing or arbitrarily arranged innervation zones. Methods: This study introduces a new modeling method to design a person-specific digital twin that enables the prediction of muscle activations during FES on the forearm. The designed individual model consists of three parts: an anatomically based 3D volume conductor, a muscle-specific nerve fiber arrangement in various regions of interest (ROIs), and a standard nerve model. All processes were embedded in scripts or macros to enable automated changes to the model and the simulation setup. Results: The experimental evaluation of simulated strength-duration diagrams showed good coincidence. The relative differences of the simulated amplitudes to the mean amplitude of the four experiments were in the same range as the inter-experimental differences, with mean values between 0.005 and 0.045. Based on these results, muscle-specific activation thresholds were determined and integrated into the simulation process. With this modification, simulated force-intensity curves showed good agreement with additionally measured curves. Discussion: The results show that the model is suitable for simulating realistic muscle-specific activations. Since complex hand movements are physiologically composed of individual, selective muscle activations, it can be assumed that the model is also suitable for simulating these movements. Therefore, this study presents a new and very promising approach for developing new applications and products in the context of the rehabilitation of sensorimotor disorders.

Combining Cyproheptadine Hydrochloride With Targeted Muscle Activation Training to Treat Upper Extremity Stroke: A Randomized, Placebo-Controlled Trial.

OBJECTIVE: To examine a treatment for upper extremity impairment in stroke survivors that combines administration of cyproheptadine hydrochloride with repetitive practice focused on control of muscle activation patterns. DESIGN: Double-blind, randomized controlled trial. SETTINGS: Laboratory within a free-standing rehabilitation hospital. PARTICIPANTS: A total of 94 stroke survivors with severe, chronic hand impairment were randomly assigned to 1 of 4 treatment groups. INTERVENTIONS: Participants received either a placebo or cyproheptadine hydrochloride in identical pill form. The daily dosage of cyproheptadine/placebo was gradually increased from 8 to 24 mg/d over 3 weeks and then maintained over the next 6 weeks while participants completed 18 therapy sessions. Therapy consisted of either (1) active practice of muscle activation patterns to play "serious" computer games or control a custom hand exoskeleton or (2) passive, cyclical finger stretching imposed by the exoskeleton. MAIN OUTCOME MEASURES: Hand control was evaluated with the primary outcome measure of time to complete the Graded Wolf Motor Function Test (GWMFT) and secondary outcome measures including finger strength and spasticity. RESULTS: Across the 88 participants who completed the study, a repeated-measures analysis of variance revealed a significant effect of GroupxEvaluation interaction on GWMFT (F=1.996, P=.026). The 3 groups receiving cyproheptadine and/or actively practicing muscle activation pattern control exhibited significant reduction in mean time to complete the GWMFT tasks; roughly one-third of these participants experienced at least a 10% reduction in completion time. Gains were maintained at the 1-month follow-up evaluation. The group receiving placebo and passive stretching did not show improvement. No significant differences among groups were observed in terms of changes in strength or spasticity. CONCLUSIONS: Despite chronic, severe impairment, stroke survivors were able to complete the therapy focused on muscle activations and achieved statistically significant improvement in hand motor control. Cyproheptadine hydrochloride is a potential complementary treatment modality for stroke survivors with hand impairment.

Transcutaneous auricular vagus nerve stimulation modulates masseter muscle activity, pain perception, and anxiety levels in university students: a double-blind, randomized, controlled clinical trial.

Introduction: Chronic anxiety is a statemarked by sustained activation of the masseter muscle, manifesting in both mental and physical strain. This prolonged tension can significantly impact mental wellbeing and cognitive abilities, posing a risk for a range of health complications. This double-blind, randomized, controlled clinical trial investigated the impact of transcutaneous auricular vagus nerve stimulation (TAVNS) on masseter muscle activity, pressure pain threshold (PPT), and anxiety levels in university students with elevated anxiety. Methods: Forty-two participants meeting inclusion criteria were randomly assigned to either active TAVNS or sham TAVNS groups. Various parameters, including masseter muscle electromyographic (EMG) signals, PPT, and Beck Anxiety Inventory (BAI) scores, were assessed before pretreatment, immediately after the intervention week, and 2 weeks follow-up. Results: Active TAVNS significantly reduced both left and right masseter activation during resting mandibular position, persisting for 2 weeks post-intervention. Additionally, TAVNS induced a lasting decrease in both left and right masseter PPT, indicative of altered pain perception. Notably, BAI scores showed a substantial reduction, emphasizing TAVNS as a potential intervention for anxiety, with effects maintained at the 2-week follow-up. Discussion: This study provides comprehensive insights into the multifaceted effects of TAVNS on physiological and psychological aspects associated with anxiety in university students. The promising results underscore TAVNS as a potential neuromodulatory intervention for anxiety-related conditions, warranting further research and clinical exploration. Clinical Trial Registration: https://ensaiosclinicos.gov.br/rg/RBR-4s4kt2r.

Positional Analysis of Assisting Muscles for Handling-Assisted Exoskeletons.

In order to better design handling-assisted exoskeletons, it is necessary to analyze the biomechanics of human hand movements. In this study, Anybody Modeling System (AMS) simulation was used to analyze the movement state of muscles during human handling. Combined with surface electromyography (sEMG) experiments, specific analysis and verification were carried out to obtain the position of muscles that the human body needs to assist during handling. In this study, the simulation and experiment were carried out for the manual handling process. A treatment group and an experimental group were set up. This study found that the vastus medialis muscle, vastus lateralis muscle, latissimus dorsi muscle, trapezius muscle, deltoid muscle and triceps brachii muscle require more energy in the process of handling, and it is reasonable and effective to combine sEMG signals with the simulation of the musculoskeletal model to analyze the muscle condition of human movement.

The Effects of Post-Exercise Cold Water Immersion on Neuromuscular Control of Knee.

To date, most studies examined the effects of cold water immersion (CWI) on neuromuscular control following exercise solely on measuring proprioception, no study explores changes in the brain and muscles. The aim of this study was to investigate the effects of CWI following exercise on knee neuromuscular control capacity, and physiological and perceptual responses. In a crossover control design, fifteen participants performed an exhaustion exercise. Subsequently, they underwent a 10 min recovery intervention, either in the form of passively seated rest (CON) or CWI at 15 °C. The knee proprioception, oxygenated cerebral hemoglobin concentrations (Δ[HbO]), and muscle activation during the proprioception test, physiological and perceptual responses were measured. CWI did not have a significant effect on proprioception at the post-intervention but attenuated the reductions in Δ[HbO] in the primary sensory cortex and posterior parietal cortex (p < 0.05). The root mean square of vastus medialis was higher in the CWI compared to the CON. CWI effectively reduced core temperature and mean skin temperature and improved the rating of perceived exertion and thermal sensation. These results indicated that 10 min of CWI at 15 °C post-exercise had no negative effect on the neuromuscular control of the knee joint but could improve subjective perception and decrease body temperature.

Alternative muscle synergy patterns of upper limb amputees.

Myoelectric hand prostheses are effective tools for upper limb amputees to regain hand functions. Much progress has been made with pattern recognition algorithms to recognize surface electromyography (sEMG) patterns, but few attentions was placed on the amputees' motor learning process. Many potential myoelectric prostheses users could not fully master the control or had declined performance over time. It is possible that learning to produce distinct and consistent muscle activation patterns with the residual limb could help amputees better control the myoelectric prosthesis. In this study, we observed longitudinal effect of motor skill learning with 2 amputees who have developed alternative muscle activation patterns in response to the same set of target prosthetic actions. During a 10-week program, amputee participants were trained to produce distinct and constant muscle activations with visual feedback of live sEMG and without interaction with prosthesis. At the end, their sEMG patterns were different from each other and from non-amputee control groups. For certain intended hand motion, gradually reducing root mean square (RMS) variance was observed. The learning effect was also assessed with a CNN-LSTM mixture classifier designed for mobile sEMG pattern recognition. The classification accuracy had a rising trend over time, implicating potential performance improvement of myoelectric prosthesis control. A follow-up session took place 6 months after the program and showed lasting effect of the motor skill learning in terms of sEMG pattern classification accuracy. The results indicated that with proper feedback training, amputees could learn unique muscle activation patterns that allow them to trigger intended prosthesis functions, and the original motor control scheme is updated. The effect of such motor skill learning could help to improve myoelectric prosthetic control performance.

Effect of the 'Pilates stance' and Pilates-based matwork training on measurements of height, waist circumference, and interscapular distance.

BACKGROUND: Standardised guidelines for stance are used to improve interobserver reliability in anthropometric measurements in clinical practice. A key feature of the stance in Pilates is the 'drawing in and up' of the abdomen. The aim of this study was to study the impact of the Pilates stance on height, waist circumference and interscapular distance, compared to that recommended in clinical practice. METHODS: 48 healthy females (median age 60 years) were assessed before and after 10-week Pilates-based matwork training. One Pilates expert and one novice took independent measurements of weight, height, waist circumference and interscapular distance (ISD). RESULTS: Pilates stance, compared to Normal, increased height by up to 2.7 cm and decreased waist up to 5.2 cm (each P < 0.001, repeated measures ANOVA). ISD decreased up to 14 mm (P < 0.001) and this decrease was greater after training (P < 0.001). After controlling for age and length of time learning Pilates, greater baseline ISD predicted a greater change in ISD after the intervention. Effect of Pilates stance was greater when the expert took the measurements (each P ≤ 0.001). CONCLUSIONS: Activation of trunk muscles in the Pilates stance increases height and decreases waist circumference, compared to the stance recommended in UK healthcare settings. A decrease in ISD was observed, which was greater after a Pilates-based matwork programme. There are significant inter-observer differences, therefore current clinical guidelines for stance are recommended for repeated anthropometry. The value of the Pilates stance in improving posture and the role of ISD as a marker, should be further studied in various contexts, including clinical settings.

Immediate but not prolonged effects of submaximal eccentric vs concentric fatiguing protocols on the etiology of hamstrings' motor performance fatigue.

PURPOSE: Our study aimed to compare the immediate and prolonged effects of submaximal eccentric (ECC) and concentric (CON) fatiguing protocols on the etiology of hamstrings' motor performance fatigue. METHODS: On separate days, 16 males performed sets of 5 unilateral ECC or CON hamstrings' contractions at 80% of their 1 Repetition Maximum (1 RM) until a 20% decrement in maximal voluntary isometric contraction (MVC) torque was reached. Electrical stimulations were delivered during and after MVCs at several time points: before, throughout, immediately after (POST) and 24 h (POST 24) after the exercise. Potentiated twitch torques (T100 and T10, respectively) were recorded in response to high and low frequency paired electrical stimulations, and hamstrings' voluntary activation (VA) level was determined using the interpolated twitch technique. For statistical analysis, all indices of hamstrings' motor performance fatigue were expressed as a percentage of their respective baseline value. RESULTS: At POST, T100 (ECC: -13.3%; CON: -9.7%; p < 0.001), T10 (ECC: -5.1%; CON: -11.8%; p < 0.05) and hamstrings' VA level (ECC: -3.0%; CON: -2.4%; p < 0.001) were significantly reduced from baseline, without statistical differences between fatigue conditions. At POST24, all indices of hamstrings' motor performance fatigue returned to their baseline values. CONCLUSION: These results suggest that the contribution of muscular and neural mechanisms in hamstrings' motor performance fatigue may not depend on contraction type. This may have implications for practitioners, as ECC and CON strengthening could be similarly effective to improve hamstrings' fatigue resistance.