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Purpose This study aimed to explore the differences in muscle activity, handwriting legibility, and consistency when using the 4 primary handwriting grip styles: dynamic quadrupod (DQ), dynamic tripod, lateral quadrupod (LQ) and lateral tripod. Study Design and Methods Thirty-four 18-22-year-old participants completed a handwriting legibility test on paper as well as consistency and metrics tests using both surface electromyography and a digital writing tablet. Electromyography was used to measure the activity of 6 muscles associated with handwriting, and the tablet measured stroke duration, length, velocity, and pen pressure. Subjects used each grip style with all protocols and scores were normalized to their native grip. Significance was set at P Results Females had a lower range in legibility scores than males by 3.5% ± 1.7% (p = .046, d = 0.713), but grip style did not impact legibility. The upper trapezius (UT) was more active in the lateral tripod and LQ grips compared to DQ by 16.8% ± 5.2% and by 13.8% ± 5.2%, (p = .007, p = .012, respectively, partial η2 = 0.188). The stroke duration was greater in the LQ grip style than dynamic tripod and DQ grip styles (p = .008, p = .023, respectively; partial η2 = 0.123). Conclusions Lateral grip styles involve more whole-arm, stabilizing movements while dynamic grip styles require fine dexterous movements. Furthermore, females are likely to be able to employ any grip with minimal effect on legibility. For a patient needing guidance in rehabilitation, understanding the differences in grips could aid selection of the optimum grip style to employ based on their muscular control deficits.

Context The single-legged squat (SLS) is appropriate for targeting activation, strengthening, and neuromuscular retraining of the gluteus maximus, gluteus medius, and quadriceps. However, the effects of different nonstance-limb positions on muscle activity have not been fully evaluated. Objective To compare the muscle activity of selected stance-limb hip muscles during the SLS using 3 nonstance-limb positions: in front (SLS-Front), in the middle (SLS-Middle), and in back (SLS-Back). Design Controlled laboratory study. Setting Biomechanics laboratory. Patients or Other Participants A total of 17 healthy adults (8 men, 9 women; age = 22.6 ± 3.6 years, height = 173.3 ± 10.7 cm, mass = 71.2 ± 11.0 kg) participated. Main Outcome Measure(s) Surface electromyographic data of the gluteus maximus, gluteus medius, lateral hamstrings, medial hamstrings, rectus femoris, and tensor fascia lata (TFL) as well as kinetic data of the hip and knee were collected while participants performed the 3 SLS tasks. Mean muscle-activation levels during the descent and ascent phases for the selected hip muscles and hip and knee kinetics in all 3 planes were compared for the 3 tasks. Each variable of interest was analyzed using a separate linear regression model with a generalized estimating equations correction. Results Muscle-activation levels of the gluteus maximus, gluteus medius, medial hamstrings, rectus femoris, and TFL for the stance limb during descent (P ≤ .04) and the medial hamstrings and TFL during ascent (P ≤ .002) were different among the SLS tasks. The greatest number of differences occurred between SLS-Front and SLS-Back. During descent, gluteal muscle activity was greater in SLS-Front (P ≤ .03) and SLS-Middle (P = .03) than in SLS-Back. For both phases, TFL activity was greater during SLS-Front than during both SLS-Middle and SLS-Back (P ≤ .006). Kinetic differences at the hip and knee between SLS tasks were also observed (P values ≤ .02). Conclusions The 3 SLS tasks had different muscle-activation and kinetic profiles. Clinicians and researchers can vary nonstance-limb position during the SLS to manipulate muscle-activation levels and tailor the exercise to assist with goals at different stages of rehabilitation.

Sex, head and neck posture, and cervical muscle preparation are contributing factors in the severity of head and neck injuries. However, it is unknown how these factors modulate the head kinematics. In this study, twenty-four (16 male and 8 female) participants experienced 50 impulsive forces to their heads with and without an acoustic warning. Female participants demonstrated a 71 ms faster (p = 0.002) muscle activation onset compared to males after warning. The magnitude of muscle activation was not significant between sexes. Females exhibited 21% (p < 0.008) greater peak angular velocity in all force directions and 18% (p < 0.04) greater peak angular acceleration in sagittal plane compared to males. Females exhibited 15% (p = 0.03) greater peak linear acceleration compared to males only in sagittal flexion. Preparation attenuated head kinematics significantly (p < 0.03) in 11 out of 18 investigated head kinematics for both sexes. A warning eliciting a startle response 420 ms prior to the impact resulted in significant attenuation of all measured head kinematics in sagittal extension (p < 0.037). In conclusion, both sex and warning type were significant factors in head kinematics. These data provide insight into the complex relationship of muscle activation and sex, and may help identify innovative strategies to reduce head and neck injury risk in sports.

Objectives/hypothesis Phonation threshold pressure (Pth ) is the minimum subglottic pressure required to reach phonation onset and is considered a marker for vocal efficiency and health. We investigated the effects of intrinsic laryngeal muscle (ILM) activation on Pth . Study design In vivo animal study. Methods In an in vivo canine phonation model, laryngeal adductor muscles were activated together by stimulation of the recurrent laryngeal nerves (RLNs) and individually via stimulation of respective terminal nerve branches. Cricothyroid (CT) muscles were activated via stimulation of the superior laryngeal nerves. ILMs were activated in a graded manner at various combinations as transglottal airflow was gradually increased. Aerodynamic and glottal posture parameters were measured at phonation onset. Results Graded RLN stimulation decreased glottal distance and increased Pth . Thyroarytenoid (TA) muscle activation alone increased Pth . Lateral cricoarytenoid (LCA) muscle activation alone had minimal effects. However, graded TA activation as a function of LCA activation level revealed a synergistic relationship between the two muscles in increasing Pth . Effects of CT activation were dependent on adductor stimulation level: CT activation increased Pth at low RLN stimulation levels and decreased Pth at high RLN levels. Conclusions The effects of ILM activation on Pth were consistent with their expected effects on vocal fold stiffness and tension. TA was the primary adductor controlling Pth . While LCA alone had minimal effects on Pth , it enhanced the role of TA in controlling Pth . TA and CT have antagonistic roles in controlling Pth . These relationships should be considered in clinical efforts to improve ease of phonation and vocal efficiency. Level of evidence N/A, basic science Laryngoscope, 2021.

AIM This study aims to examine the effect of motor imagery (MI) training on MI abilities, functional mobility, and lower extremity muscle activity in children with unilateral cerebral palsy (UCP). METHOD 34 UCP and 17 typically developing participants were included. UCP was randomised into 2 groups as UCP MI and UCP control. Participants typically developing were included for baseline comparisons. UCP MI group received 8 weeks of physiotherapy and MI training, the UCP control group 8 weeks of physiotherapy training. The MI abilities, functional mobility, and lower extremity muscle activation were assessed in all groups. RESULTS It was found that MI training made a significant difference in favour of the UCP MI group in terms of Movement Imagery Questionnaire-For Children (MIQ-C), mental chronometry, functional mobility, and resting muscle activation (p

Background and Study Aim. The aim of this study is to examine the electromyographic responses to Nordic curl and prone leg curl exercises, having two different mechanics. Material and Methods. The athletes performed the prone leg curl and Nordic curl exercises in random order, 6 repetitions each. Electromyographic data of semimemranosus, semitendinosus, biceps femoris and rectus femoris muscles were recorded by 8-channel electromyography in order to examine the muscle responses to exercises. Total duration of exercise, cumulative integrated electromyographic values and muscle activation rates in 5 different intensity zones determined according to MVC% values have been compared. Results. Prone leg curl exercise occurred in less time than Nordic curl exercise. According to the cumulative integrated electromyography data results, all muscles showed similar muscle activation in both exercises. Comparing the muscle activation rates in the five intensity zones, more muscle activity was observed for Nordic curl exercise in the first intensity zone, while prone leg curl exercise was more active in the third and fourth zones. During the prone leg curl exercise, the muscle activation rate of the dominant leg is higher in the first intensity zone, whereas the non-dominant leg in the fourth intensity zone has a higher muscle activation. During the Nordic curl exercise, the muscle activation rates of the dominant leg in the first and fifth intensity zones are higher, whereas the nondominant leg in the fourth intensity zone is higher. Conclusions. Prone leg curl exercises can be preferred in order to stimulate high muscle activation in a short time. Comparing the two exercises there was no significant difference in muscle activity in dominant and nondominant legs.

The generalized joint hypermobility (GJH) syndrome is a condition characterized by a connective tissue disorder that may negatively affect the muscle function and muscle balance in the lower limbs. The aim of study was to compare isometric and dynamic maximal strength, total work, active optimum angle, electromyographic activity strategy, and the muscle imbalance of the knee extensors and flexors using the hamstrings/quadriceps ratio (H:Q) in individuals with GJH and without GJH (NGJH). Forty healthy untrained men and women (20 with GJH and 20 without GHJ) participated in the study. Dynamic, isometric (30° and 60°) peak torque, total work, active optimum angle, and agonist and antagonist muscle activation of knee extensors and flexors were obtained. The conventional and functional H:Q ratio were calculated using peak torque, rate of torque development, muscle activation, and total work. The dynamic and isometric peak torque, total work, active optimum angle, and agonist and antagonist muscle activation were not different between GJH and NGJH (p > 0.05). Conventional and functional H:Q ratios calculated using the different neuromuscular parameters were considered below the normative values for both groups, with no difference between groups (p > 0.05). The lack of difference between groups suggests that hypermobility does not have a greater influence on maximal strength and in underlying mechanisms related to knee extensors and flexors muscle activation and muscle balance in the knee joint.

Heightened stress during air pistol competitions may impair shooters' abilities to maintain gun stability, resulting in inferior performance. This study aimed to compare the pre-trigger muscle activation levels of upper muscles in 10-m air pistol shooters between training and simulated competition conditions. Seven sub-elite shooters from the Singapore National Youth Air Pistol Team shot 30 shots in a training versus simulated competition condition in randomised orders on separate days. Muscle activation for the forearm and shoulder muscles, namely extensor carpi radialis, flexor carpi ulnaris, anterior deltoid, and posterior deltoid, were recorded using electromyography (EMG). Shooting performance was evaluated by total shot scores. Stress level was monitored via heart rate and the Mental Readiness Form-3. No statistically significant differences were found in EMG, performance, or stress-related variables between conditions, although moderate-to-large effect sizes were observed in some muscle activation and self-reported stress indicators. Analysis of individual performances using smallest worthwhile change showed that two participants improved under the simulated competition condition, while two declined, and three remained unaffected. In conclusion, sub-elite youth air pistol shooters were able to exhibit good neuromuscular control under high anxiety situations and thus their performance was largely unaffected.

BACKGROUND: Vibration exercise has been investigated to enhance muscle activation, however, the effect of different amplitude vibratory exercises on cardiovascular stress is less understood. OBJECTIVE: Our study aims to explore the acute effect of shoulder vibratory exercises with different postures and amplitudes on the cardiovascular response in healthy adults. METHODS: Using a repeated measures randomized design, 36 subjects performed three different sessions with FLEXI-BAR exercise (FBE): (1) zero-amplitude, (2) small-amplitude, (3) large-amplitude. Each session included three different shoulder positions: 45-, 90- and 180-degree flexion. Heart rate variability (HRV), heart rate (HR) and rating of perceived exertion (RPE) were monitored continuously, while systolic blood pressure (SBP), diastolic blood pressure (DBP) and rate-pressure product (RPP) were measured before and after each exercise session. RESULTS: Compared with zero-amplitude, both small- and large-amplitude FBE protocols induced higher SBP. By contrast, DBP decreased with small- and large-amplitude. The RPP immediately after the exercise session were higher than at baseline. For high frequency, low frequency of HRV and HR there was a main effect of amplitude. CONCLUSION: Small- and large-amplitude FBE increased significantly SBP, RPE, HRV, HR and induced lower DBP, but the changes were modest, suggesting that FBE impose no extra threats to cardiovascular stress.

What is the central question of this study? Is there a critical threshold beyond which the loss of muscle contractility is regulated by the level of muscle activation during single-limb exercise of differing intensities and volumes? What is the main finding and its importance? Plateaus in the decline in muscle contractility during single-limb knee extension depended on both exercise volume and contraction intensity. A plateau was only evident with an increase in exercise volume. Muscle activation increased and did not decline despite substantial reductions in contractility. The findings indicate that the decrease in muscle contractility exhibited by resistance-trained men during the performance of submaximal isometric contractions with the knee extensors was not regulated by the level of muscle activation.Our study examined the influence of contraction intensity and exercise volume on changes in muscle contractility and activation of the knee extensor muscles. Maximal voluntary torque (MVT) and rate of change in torque, surface electromyograms, voluntary activation, V-waves and quadriceps resting twitch measures were assessed in 10 resistance-trained men during two experimental sessions. Each session began with an initial baseline series of contractions at a fixed intensity of 40% or 80% MVT. The 40%-only session continued with five contractions to task failure at 40% MVT. The 80% session continued with five contractions to failure each at 80%, 60% and 40% MVT. Greater reductions in MVT were observed during the baseline contractions of the 40%-only session compared with the 80% session at each matched-volume time point (P 0.05), with similar changes in twitch values (P 0.001). MVT and twitch values plateaued at each intensity during the 80% session and were significantly different across intensities: 80%60%40% (P 0.001). There were no differences for measures during the five contractions at 40% MVT performed on the different days, despite a greater volume of exercise performed prior to the 40% MVT during the 80% session. At each contraction intensity, a plateau in contractility loss was observed as more contractions were performed. We found that initial increases in muscle activation were maintained in the presence of increases in exercise volume and, in contrast to the critical-threshold hypothesis, did not decline in parallel with reductions in muscle contractility.

Introduction Some people with Parkinson’s disease (PD) frequently have an unsteady gait with shuffling, reduced strength, and increased rigidity. This study has investigated the difference in the neuromuscular strategies of people with early-stage PD, healthy older adults (HOA) and healthy young adult (HYA) during short-distance walking. Method Surface electromyogram (sEMG) was recorded from tibialis anterior (TA) and medial gastrocnemius (MG) muscles along with the acceleration data from the lower leg from 72 subjects—24 people with early-stage PD, 24 HOA and 24 HYA during short-distance walking on a level surface using wearable sensors. Results There was a significant increase in the co-activation, a reduction in the TA modulation and an increase in the TA-MG lateral asymmetry among the people with PD during a level, straight-line walking. For people with PD, the gait impairment scale was low with an average postural instability and gait disturbance (PIGD) score = 5.29 out of a maximum score of 20. Investigating the single and double support phases of the gait revealed that while the muscle activity and co-activation index (CI) of controls modulated over the gait cycle, this was highly diminished for people with PD. The biggest difference between CI of controls and people with PD was during the double support phase of gait. Discussion The study has shown that people with early-stage PD have high asymmetry, reduced modulation, and higher co-activation. They have reduced muscle activity, ability to inhibit antagonist, and modulate their muscle activities. This has the potential for diagnosis and regular assessment of people with PD to detect gait impairments using wearable sensors.

Although previous studies have shown that powered exoskeletons reduce muscle activation while walking across participants, less is known about how they impact an individual’s muscle activation. This study examined an individual’s muscle activity during walking with a powered ankle exoskeleton. The designed human-exoskeleton coordination was defined as a decrease in medial gastrocnemius (MGAS) muscle activation with the exoskeleton powered and increase with the exoskeleton unpowered. 60% of the participants were observed to coordinate with the exoskeleton as designed, with 67% showing a decrease in RMS MGAS during adaptation. 60% of the participants showed no change during the de-adaptation, with 47% not returning to baseline metrics by late de-adaptation. Muscle activity differs between individuals in response to the exoskeleton power state and over time within the power state. It is important to consider these different behaviors when integrating exoskeletons into occupational settings as adaptation may be supported by training and experience.

Purpose The present study examined acute normobaric hypoxic exposure on the number of repetitions to failure, electromyographic (EMG) repetition duration (Time), EMG root mean square (RMS) and EMG mean power frequency (MPF) during biceps brachii (BB) dynamic constant external resistance (DCER) exercise. Methods Thirteen subjects performed two sets of fatiguing DCER arm curl repetitions to failure at 70% of their one repetition maximum under normoxic (NH), moderate hypoxia FiO2 = 15% (MH) and severe hypoxia FiO2 = 13% (SH). Electromyography of the BB was analyzed for EMG Time, EMG RMS, and EMG MPF. Repetitions were selected as 25%, 50%, 75%, and 100% of total repetitions (%Fail) completed. Pulse oximetry (SpO2) was measured pre-and post-fatigue. Results There was no significant three-way (Condition x Set x %Fail) or two-way (Condition x Set) interaction for any variable. The number of repetitions to failure significantly decreased from (mean ± SEM) 18.2 ± 1.4 to 9.5 ± 1.0 with each Set. In addition, EMG Time increased (25% 75%>100%), and EMG MPF decreased (75% > 100%) as a result of fatiguing exercise. SpO2 was lower during MH (Δ5.3%) and SH (Δ9.2%) compared to NH and as a result of fatiguing exercise increased only in MH (Δ2.1%) and SH (Δ5.7%). Conclusion The changes in BB EMG variables indicated exercise caused myoelectric manifestations of fatigue, however, acute moderate or severe hypoxia had no additional influence on the rate of fatigue development or neuromuscular parameters., Highlights • Acute MH (FiO2 15%) and SH (FiO2 14%) did not alter the muscle contractile process. • Arm curl repetitions to failure decreased MU recruitment and conduction velocity. • EMG fatigue analysis, hypoxia and arm curls to failure, EMG RMS, EMG MPF and Time. • SpO2 was lower at MH and SH which increased following fatiguing exercise.

Hoe is an important hand tool used by the farmers across India for land preparation and digging work. Continuous and repeated use of hoe in awkward posture results in severe work-related musculoskeletal distress. The main objective of this study was to investigate the effect of hoe handle length and angle on arm and shoulder muscle engagement and subject preference. For this purpose, two modified hoes with different handle lengths were utilized to perform land preparation work and their muscle engagement was compared with a traditional land preparation activity. Ten volunteers participated in this experimental study and their muscle activities on biceps brachii (bilateral) and trapezius muscle (bilateral) during continuous land preparation process were recorded using surface electromyography (sEMG) sensors. Subjective discomfort rating was carried out using Borg’s CR-10 scale. Results revealed that Model 1 with medium handle length had reduced the muscle activation on arm and shoulders. Subjective preference results revealed that biceps brachii muscles followed by trapezius left muscle had high rate of discomfort during the land preparation work.

PURPOSE: Gum chewing stimulates the sympathetic nervous system and increases energy consumption. However, the effect of mastication on physical activity remains unclear. This study aimed to investigate the effect of gum masticatory movement on physiological markers related to walking and muscle activation during cycling in different patient groups.METHODS: Using a randomized crossover design, 25 participants participated in walking trials with a 1-week washout; the trials included chewing gum (GUM), taking a candy with the same ingredients as the gum (CAN), and no ingestion (CON). Energy expenditure (EE), metabolic equivalent (MET), oxygen consumption (VO2), and heart rate were measured using a portable metabolic device. The walking distance was also calculated. In the cycling experiment, the other 19 participants randomly completed 7 minutes of the three trials (GUM, CAN, CON) with a 15-minute break. The mean cycling period (MCP), cycle number (CN), coefficient of variation of the cycling period (CV), and integrated electromyography (iEMG) results were measured using the Delsys Trigno™ Wireless EMG System.RESULTS: The walking distance was significantly higher in the GUM group than in the CAN and CON groups by an average of 78 m (7.4%, p2 demonstrated a partially significant increase after 15 minutes. In the cycling experiment, there were no significant differences in the effects of the trials on cycling performance (MCP, CN, CV). However, significant differences were observed in the GUM group for the iEMG results.CONCLUSIONS: Our study results suggest that gum chewing improves physical performance, such as walking distance, and improves energy metabolism, such as EE and METs. Additionally, it can influence the improvement in the lower limb muscle activity during cycling.

Background: Occupational footwear and a prolonged duration of walking have been previously reported to play a role in maintaining postural stability. The purpose of this paper was to analyze the impact of three types of occupational footwear: the steel-toed work boot (ST), the tactical work boot (TB), and the low-top work shoe (LT) on previously unreported lower extremity muscle activity during postural stability tasks. Methods: Electromyography (EMG) muscle activity was measured from four lower extremity muscles (vastus medialis (VM), medial hamstrings (MH), tibialis anterior (TA), and medial gastrocnemius (MG) during maximal voluntary isometric contractions (MVIC) and during a sensory organization test (SOT) every 30 min over a 4 h simulated workload while wearing ST, TB, and LT footwear. The mean MVIC and the mean and percentage MVIC during each SOT condition from each muscle was analyzed individually using a repeated measures ANOVA at an alpha level of 0.05. Results: Significant differences (p &lt, 0.05) were found for maximal exertions, but this was limited to only the time main effect. No significant differences existed for EMG measures during the SOT. Conclusion: The findings suggest that occupational footwear type does not influence lower extremity muscle activity during both MVIC and SOT. Significantly lower muscle activity during maximal exertions over the course of the 4 h workload was evident, which can be attributed to localized muscular fatigue, but this was not sufficient to impact muscle activity during postural stability tasks.

BACKGROUND: Few studies have reported the contribution of isometric-specific exercise of the biceps brachii muscle to increased strength under manual fixation of the scapula. OBJECTIVE: To investigate the activation amplitude of the biceps brachii (BB), serratus anterior (SA), and upper trapezius (UT) in a supine lying posture based on various exercise conditions. METHODS: The EMG activity of BB, SA, and UT was measured in 25 healthy adults while performing maximal elbow flexion exercise with or without manual stabilization of the scapula in two different loading conditions. RESULTS: Muscle activation of the BB was significantly greater when performed with manual fixation of the scapula under the wrist-loading exercise condition (p< 0.05) but manual fixation of the scapula or absence thereof did not have an effect. Elbow flexion force was significantly increased when applying manual fixation to the scapula in both the hand and wrist-loading exercise conditions (p< 0.05). There were no interaction effects between exercise conditions and manual fixation (with or without) in any of the EMG activation values (p> 0.05). CONCLUSION: Manual stabilization of the scapula is a useful therapeutic technique to increase BB strength. Such an intervention may also be indicated for accurate strength measurement of this muscle.

Background: Shin splint is one of the most common sports injuries after strenuous exercise. Kinesiology taping (KT) is a popular noninvasive remedy used in sports-related disorders, with the potential effects of relieving pain, facilitating proprioception, modulating muscle activation and correcting abnormal movement patterns. However, the exact efficacy of KT on shin splints is still unknown, and previous findings are inconsistent. Hence, this study aimed to conduct a systematic review to evaluate the current status of relevant evidence on its efficacy. Methods: The review was performed according to the PRISMA guidelines, and a systematic search of the literature was conducted in December 2020. Electronic databases, Embase, Scopus, Medline, Web of Science, PubMed and Biomed Central were searched for the identification of pertinent studies with pre-defined key terms on shin splints and KT. Results: Four studies with a total sample size of 141 participants were included and analyzed. Two studies had within-subject designs, whereas the other two were randomized clinical trials. Although the positive results of KT were reported by the studies, methodological quality varied from poor to moderate according to the Physiotherapy Evidence Database Scale or Non-Randomized Studies-of Interventions. Conclusion: In conclusion, this review revealed that the efficacy of KT on shin splints remains not clear. Evidence that supports its effectiveness in individuals with shin splints is currently limited. Further studies with good methodological quality and study design are warranted.

The main purpose of the present study was to investigate maturation-related changes in force-related factors in gymnasts and untrained girls. A total of 60 female participants were divided into two groups of gymnasts and untrained individuals. Each group had three subgroups of preadolescents, adolescents, and adults according to Tanner's scale. Informed consent forms were obtained from each participant. After familiarity and initial measurements, each subject performed three maximal voluntary isometric contractions (MVIC) of the knee extensors at five different angles to determine the optimal angle of force production. The rate of force development (RFD) was calculated using the torque data. The EMG signal of the rectus femoris muscle was recorded during the MVIC test to measure voluntary activation (RMS). Gymnasts had more absolute torque in all three age groups (P

Introduction Vibratory asymmetry and neuromuscular compensation are often seen in laryngeal neuromuscular pathology. However, the ramifications of these findings on voice quality are unclear. This study investigated the effects of varying levels of vibratory asymmetry and neuromuscular compensation on cepstral peak prominence (CPP), an analog of voice quality. Study design In vivo canine phonation model. Methods Varying degrees of vocal fold vibratory asymmetry were achieved by stimulating one recurrent laryngeal nerve (RLN) over 11 levels from threshold to maximal muscle activation. For each of these levels, phonation was induced at systematically varied combinations of neuromuscular compensation: three levels each of contralateral RLN stimulation (80%, 90%, and 100% of maximal), superior laryngeal nerve (SLN) activation (0%, 50%, and 100% of maximal), and airflow levels (500, 700, and 900 mL/s). Vocal fold symmetry was determined by assessing the opening phase of the vibratory cycle in high-speed video recordings. Voice quality was estimated acoustically by calculating CPP for each voice sample. Results Eight hundred twenty-two phonatory conditions with varying degrees of vibratory asymmetry were evaluated. CPP was highest at vibratory symmetry. Increasing levels of asymmetry resulted in significant decreases in CPP. CPP increased significantly with increasing contralateral RLN activation. CPP was significantly higher at 50% SLN activation than 0% or 100% SLN activation. Conclusion Voice quality, as approximated by CPP, is best at vibratory symmetry and deteriorates with increasing degrees of asymmetry. Voice quality may be improved with neuromuscular compensation by increased adduction of the contralateral vocal fold or increased vocal fold tension at mid-levels of SLN activation. Level of evidence N/A, Basic Science Laryngoscope, 2021.

Muscles work synergistically to support the body during landing. Myofascial meridians have been described to classify muscles into functional synergies. The role that these functional lines plays in positioning the trunk and lower extremity of patients with anterior cruciate ligament reconstruction (ACLR) and healthy athletes during drop landing tasks remains unclear.The purpose of this study was to compare the front and back functional lines (FFL and BFL) muscle activation in patients with ACLR and healthy participants during single leg vertical drop jump (SLVDJ).Thirty-two male athletes (post-ACLR = 16, healthy = 16) participated (age = 23.3 ± 2.3 years). Superficial electromyography of FFL (adductor longus [AL], rectus abdominis [RA], pectoralis major) and BFL (vastus lateralis [VL], gluteus maximus [GMax], latissimus dorsi [LD]) was collected during the SLVDJ and compared at initial contact and maximum knee flexion between groups using t-tests and limbs using paired-samples t-tests.In the FFL, the AL (p0.05) and RA (p0.05) muscles were more active in the healthy group compared to the ACLR group at initial contact and maximum knee flexion. PM demonstrated greater activation in the healthy group only at maximum knee flexion (p0.05). In the BFL, the VL (p0.05) and GMax (p0.05) muscles were more active in the ACLR group, whereas the LD (p0.05) muscles demonstrated greater activation in the healthy group at initial contact and maximum knee flexion. There were no healthy group inter-limb differences in FFL and BFL activation. ACLR participants demonstrated greater non-injured limb VL, AL, GMax and LD activation (p0.05) and greater injured limb PM and RA activation (p0.05).Based on the present data, patients after ACLR may present with an alteration in BFL and FFL muscles activation during a drop jump task. Functional line muscles during dynamic activities may change lower extremity positioning and lead to increase ACL injury risk.

Background The aim of this study was to examine the effect of two different wrist immobilization methods on the muscle activation of the upper trapezius muscle and functional typing performance during computer typing tasks in office workers. Methods The study was conducted on 11 healthy office workers. The study subjects were asked to type on a computer for 5 min (1) without splint or taping, (2) with a splint, (3) with rigid taping which limits the wrist flexion at the dominant side. The upper trapezius muscle activation was recorded by surface EMG during the task. The mean values obtained from EMG were normalized according to Maximum Voluntary Isometric Contraction (MVIC), comparisons were made according to %MVIC. Results The office workers’ mean age was 27.45 ± 3.64 years. There was no significant difference in immobilization methods between %MVIC on dominant (p = .508) and non-dominant (p = .213) sides. The upper trapezius of the non-dominant side showed higher electromyographic activity when the subjects used a splint (p = .013). There was a significant difference between splinting and rigid taping methods in typing performance (z = −2,491, p = .013). Conclusion There is no significant difference in the upper trapezius muscle activation between the splint and rigid taping methods during the computer typing task on the dominant side. The typing performance was affected more during splint use compared to rigid tape application. Considering the importance of work efficiency in employees, rigid taping might be considered as an alternative splinting for wrist immobilization in office workers.

Elderly patients face difficulty in performing the sit-to-stand motion; hence, their dependency on assistive devices for activities of daily living is increasing. However, the existing devices do not provide support according to the individual's characteristics. This study aimed to develop a sit-to-stand motion assistive chair that detects the user's weight using a load sensor and assists them to stand up by adjusting the speed themselves as per their weight and preference. Additionally, we investigated the feasibility of the developed device. A device for assisting patients in the sit-to-stand motion in rising up from the chair by electrical motorization was developed. This device senses the load on the seat plate using the load sensor and transmits it to the display through which the users can control the speed themselves using the speed control device. To test its feasibility, the electromyographic muscle activation was analyzed for the erector spinae, quadriceps, tibialis anterior, and gastrocnemius muscles in the sit-to-stand motion using this device in five healthy adults. When compared with the non-use of the device, the use of the developed assistive chair device significantly decreased the muscle activation of the erector spinae, quadriceps, tibialis anterior, and gastrocnemius by 37.27%, 20.44%, 14.50%, and 10.56% on the left and by 17.98%, 24.48%, 32.61%, and 6.05% on the right, respectively. The assistive device with a pressure sensor can effectively assist elderly patients with reduced muscle strength and balance in performing the sit-to-stand motion.

Purpose To examine the influence of hip abductor strength, neuromuscular activation, and pelvis and femur morphology in contributing to sex differences in hip adduction during running. In addition, we sought to determine the best predictors of hip adduction during running for both men and women. Methods Fifteen female runners and 14 male runners underwent strength testing, instrumented overground running (e.g., kinematics and muscle activation), and computed tomography scanning of pelvis and femur. Morphologic measurements included bilateral hip width to femur length ratio, acetabulum abduction, acetabulum anteversion, femoral anteversion, and femoral neck-shaft angles. Sex differences for all variables were examined using independent t tests. Linear regression was used to assess the ability of each independent variable of interest to predict peak hip adduction during the late swing and stance phase of running. Results Compared with men, women exhibited significantly greater peak hip adduction during both late swing (8.5° ± 2.6° vs 6.2° ± 2.8°, P = 0.04) and stance phases of running (13.4° ± 4.2° vs 10.0° ± 3.2°, P = 0.02). In addition, women exhibited significantly lower hip abductor strength (1.8 ± 0.3 vs 2.0 ± 0.3 N·m·kg-1, P = 0.04), greater femoral neck-shaft angles (134.1° ± 5.0° vs 129.9° ± 4.1°, P = 0.01), and greater hip width to femur length ratios than men (0.44 ± 0.02 vs 0.42 ± 0.03, P = 0.03). Femoral anteversion was the only significant predictor of peak hip adduction during late swing (r = 0.36, P = 0.05) and stance (r = 0.41, P = 0.03). Conclusions Our findings highlight the contribution of femur morphology as opposed to hip abductor strength and activation in contributing to hip adduction during running.

Background: The leg press is one of the most typical exercises for strengthening the lower limbs. The objectives of this study were to compare 5 inclined leg press exercise conditions, varying the feet width stance (100% or 150% hip width), the feet rotation (0° or 45° external rotation) on the footplate and using 2 different movement velocities (MVs; maximum intended, and 2:2 seconds steady-paced velocities) to determine their effect on muscle activation as well as on the kinematic parameters between trained men and trained women. Hypotheses: There will be no significant differences in muscle activation with regard to the feet position. The higher the MV, the greater the muscle activation. Study Design: A cross-sectional cohort study. Level of Evidence: Level 3. Methods: A repeated-measures between-group design was performed to examine muscle activation and kinematic parameters for the different conditions between gender groups. The level of significance was set at alpha = 0.05 for all statistical analyses. Results: Muscle activation presented no differences between conditions regarding feet width stance or feet rotation. Furthermore, muscle activation was greater during positive phases than negative phases of the exercise for all conditions and was also greater under maximum intended velocity conditions compared with steady-paced conditions. Otherwise, the muscle activation pattern presented slight differences by gender. In men, the greatest muscle activation was for the vastus medialis, followed by the vastus lateralis (VL), rectus femoris (RF), and gluteus medialis (GMED), while in women, the greatest muscle activation was for the vastus medialis, followed by the RF, VL, and GMED. Finally, greater mean propulsive velocity, maximum velocity, maximum power, and footplate displacement values were reported for men than for women under all the conditions. Conclusion: The inclined leg press exercise produces the highest muscle activation in the vastus medialis, regardless of the velocity, feet stance, or gender. Clinical Relevance: Given that there are no differences in muscle activation regarding the feet stance, a participant’s preferred feet stance should be encouraged during the inclined leg press exercise. Furthermore, the MV would preferably depend on the session objective (a training or a rehabilitation program), being aware that there is greater muscle activation at higher speeds. The inclined leg press exercise could be performed as a closed kinetic chain exercise when the main objective is to activate the vastus medialis.

Objective To investigate the effect of one’s sex and pedaling intensity on upper body muscle activation patterns during typing while cycling. Background Females are at a higher risk for computer work-related musculoskeletal disorders, and mobile workstations have been suggested to induce healthier muscular patterns compared with sitting. However, the neuromuscular characteristics of performing computer work in a cycling workstation have not been investigated. Method Twenty-two participants (10 females) completed a 60-min computer typing task while pedaling on a cycle ergometer at two different intensities (25%, 4% heart rate reserve). Surface electromyography (EMG) was recorded from seven muscles of the upper body. Effects of time, sex, and intensity were assessed for muscle activation (RMS), activation variability (CV), and normalized mutual information (NMI) via generalized estimating equations. Results With time, neck/shoulder CV increased in males during higher pedaling intensity, whereas in females it decreased during lower intensity. In females, RMS of neck/shoulder and NMI of neck/shoulder muscle pairs were lower, whereas forearm RMS was 34.2% higher with higher intensity cycling compared with lower intensity. Lower back RMS decreased 28.3% in the initial half of the task in females, but in males it increased 14.4% in the later half. Conclusion and application Cycling workstation showed a sex- and intensity-specific EMG response. These differing responses should be considered when implementing the use of cycling workstation and may be important for preventing/managing sex-specific muscle fatigue and musculoskeletal disorders.

Background Approximately 24% of physical therapists report regularly using yoga to strengthen major muscle groups. Although clinicians and athletes often use yoga as a form of strength training, little is known about the activation of specific muscle groups during yoga poses, including the gluteus maximus and medius. Hypothesis/Purpose The purpose of this study was to measure gluteus maximimus and gluteus medius activation via electromyography (EMG) during five common yoga poses. A secondary purpose of the current study was to examine differences in muscle activation between sexes and experience levels. Study Design Cross-Sectional Methods Thirty-one healthy males and females aged 18-35 years were tested during five yoga poses performed in a randomized order. Surface EMG electrodes were placed on subjects’ right gluteus maximus and gluteus medius. Subjects performed the poses on both sides following a maximal voluntary isometric contraction (MVIC) test for each muscle. All yoga pose EMG data were normalized to the corresponding muscle MVIC data. Results Highest gluteus maximus activation occurred during Half Moon Pose on the lifted/back leg (63.3% MVIC), followed by the stance/front leg during Half Moon Pose (61.7%), then the lifted/back leg during Warrior Three Pose (46.1%). Highest gluteus medius activation occurred during Half Moon Pose on the lifted/back leg (41.9%), followed by the lifted/back leg during the Warrior Three Pose (41.6%). A significant difference was found in %MVIC of gluteus medius activity between male and female subjects (p = 0.026), and between experienced and inexperienced subjects (p = 0.050), indicating higher activation among males and inexperienced subjects, respectively. Conclusion Half Moon Pose and Warrior Three Pose elicited the highest activation for both the gluteus maximus and the gluteus medius. Higher gluteus medius activation was seen in males and inexperienced subjects compared to their female and experienced counterparts. Level of Evidence 3

Background: There is some evidence that high-load lumbar stabilization exercises, such as back bridge, can recruit both local and global muscles. Hypothesis: Therapeutic exercises would optimize gluteus maximus (GMax), gluteus medius (GMed), multifidus (MF), and transversus abdominis (TrA) activation, while minimizing the activation of the tensor fascia latae (TFL) and erector spinae (ES) muscles in healthy individuals. Design: Cross-sectional study. Setting: Research laboratory. Level of Evidence: Level 4. Methods: In this cross-sectional study, surface electromyography (EMG) of GMax, GMed, TFL, TrA, MF, and ES was used to quantify the gluteal-to-TFL muscle activation (GTA) index and a ratio of local to global (L/G) lumbar muscles during (1) the elbow-toe exercise in the prone position, (2) the elbow-toe with right left lifted, (3) the hand-knee with left arm and right leg lifted, (4) the back bridge, (5) the back bridge with right leg lifted, (6) the back bridge with left leg lifted, (7) the side bridge with left leg lifted, (8) the side bridge with right leg lifted, and (9) the elbow-toe with right leg horizontally lifted exercises in healthy individuals (20 men, 20 women; age, 25 ± 4 years). Results: The back bridge exercise with left leg lift generated the highest L/G muscles activity ratio (L/G = 3.35) while the hand-knee exercise yielded the lowest L/G muscles activity ratio (L/G = 1.21). The side bridge exercise with left elbow and foot and lifting the right leg (GTA = 63.78), hand-knee exercise (GTA = 49.62), back bridge (GTA = 28.05), and elbow-toe exercise with left leg horizontally lifted (GTA = 23.02) generated the highest GTA indices, respectively. Meanwhile, the normalized EMG amplitude for GMax was significantly less than the TFL, for elbow-toe exercise ( P < 0.001), back bridge with left leg lift ( P = 0.001), side bridge exercise with the right elbow and foot and lifting the left leg ( P = 0.002), and elbow-toe exercise with right leg horizontally lifted ( P < 0.001). Conclusion: The highest GTA indexes were observed during (1) the side bridge lifting the dominant leg and (2) the hand-knee horizontally lifting dominant leg, respectively. The L/G ratio was highest during (1) the back bridge lifting nondominant leg, (2) back bridge, and (3) back bridge lifting dominant leg, respectively. This study supports the use of back bridge exercises to strengthen the MF and side bridges to improve gluteal muscle activation. Clinical Relevance: The highest GTA index was observed in the side bridge lifting the right leg. Highest L/G ratio was in the back bridge with nondominant leg lifted. This study supports the use of back bridge exercises to strengthen the MF. This study supports the use of side bridges to improve gluteal muscle activation.

This review aimed to investigate characteristics of muscle activation and ground reaction force (GRF) patterns in patients with ankle instability (AI). Relevant studies were sourced from PubMed, CINAHL, SPORTDiscus, and Web of Science through December 2019 for case-control study in any laboratory setting. Inclusion criteria for study selection were (1) subjects with chronic, functional, or mechanical instability or recurrent ankle sprains; (2) primary outcomes consisted of muscle activation of the lower extremity and GRF during landing; and (3) peer-reviewed articles with full text available, including mean, standard deviation, and sample size, to enable data reanalysis. We evaluated four variables related to landing task: (1) muscle activation of the lower extremity before landing, (2) muscle activation of the lower extremity during landing, (3) magnitude of GRF, and (4) time to peak GRF. The effect size using standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated for these variables to make comparisons across studies. Patients with AI had a lower activation of peroneal muscles before landing (SMD = -0.63, p 0.05). Altered muscle activation and GRF before and during landing in AI cases may contribute to both recurrent ankle and ACL injuries and degenerative change of articular. Key points Patients with ankle instability have a lower activation of peroneal muscles before landing. Additionally, patients with ankle instability have greater peak vertical GRF and shorter time to peak vertical GRF than those of normal subjects during landing. Altered landing strategy in cases of ankle instability may contribute both to the recurrent ankle and other injuries of the lower extremity (e.g., ACL tear and degenerative change of articular cartilage).

Measuring muscle activation via electric potential, referred to as electromyography (EMG), has traditionally been used for medical research and diagnosis of neuromuscular disorders. However, with the advent of powerful integrated circuits and micro-controllers, the EMG circuits and sensors can find their way into prosthetics, robotics and control systems. Surface electromyography and needle electromyography are two general methods of recording the electrical activities of muscle tissue. In this paper, surface electromyography is used to analyse the human arm muscle nerve signals and convert the obtained nerve signal into mechanical movement in a motor. This kind of bionic control module finds its greatest use in prosthetics. The surface detection of the nerve signals reduces the risk of operation on the amputated part of the patient and gives a proper control to the person in movement of the prosthetic arm/leg. The module has the advantage of being small and simple, and easily manageable when compared to the other available options. Further development in the module can lead to fully developed and human safe prosthetic limbs that are very much alike and do all the functions as the actual human limbs. Index Terms: Electromyography, Surface electromyography, Bio electrodes, Bionic Control, non-invasive technique, aphasia

Background: Hand grip strength is of great significant parameter in evaluation of hand function and it is most reliable clinical assessment tool of human strength. It is very useful in various professions where people must work with their hand, like physiotherapy. The core serves at the center of functional kinetic chain in alternative medicine world; the core has been referred to as the “powerhouse”, the foundation or engine of all limb movements. So the purpose of this study is to find out correlation between hand grip strength and core muscle activation in physical therapists of age group 18 to 25. Methods: Two hundred physical therapists volunteered to participate in this study were assessed for height, weight, BMI, the hand grip strength of the dominant hand and the non-dominant hand and core muscle activation. The hand grip strength was assessed with Jamar dynamometer and the core muscle activation was assessed with Pressure Biofeedback Unit. Results: Pearson’s correlation coefficient was used. The results of this study shows that there was weak positive correlation(r=0.42) between the hand grip strength of dominant hand and non-dominant hand with core muscle activation. Conclusion: This study shows weak correlation between the hand grip strength with core muscle activation. Key words: Hand grip strength, Hand dynamometer, Core muscle strength, Pressure Biofeedback Unit.

PURPOSE This study aimed to investigate the changes in lower limb kinematics, kinetics, and muscle activation during a high-intensity run to fatigue (HIRF). METHODS Eighteen male and female competitive middle-distance runners performed a HIRF on an instrumented treadmill at a constant but unsustainable middle-distance speed (~3 min) based on a preceding maximum oxygen uptake (V˙O2max) test. Three-dimensional kinematics and kinetics were collected and compared between the start, 33%, 67%, and the end of the HIRF. In addition, the activation of eight lower limb muscles of each leg was measured with surface EMG (sEMG). RESULTS Time to exhaustion was 181 ± 42 s. By the end of the HIRF (i.e., vs the start), ground contact time increased (+4.0%), whereas flight time (-3.2%), peak vertical ground reaction force (-6.1%), and vertical impulse (-4.1%) decreased (all P < 0.05), and joint angles at initial contact became more (dorsi)flexed (ankle, +1.9°; knee, +2.1°; hip, +3.6°; all P < 0.05). During stance, by the end of the HIRF: peak ankle plantarflexion moment decreased by 0.4 N·m·kg-1 (-9.0%), whereas peak knee extension moment increased by 0.24 N·m·kg-1 (+10.3%); similarly, positive ankle plantarflexion work decreased by 0.19 J·kg-1 (-13.9%), whereas positive knee extension work increased by 0.09 J·kg-1 (+33.3%; both P < 0.05) with no change in positive hip extension work. Hip extensor surface EMG amplitude increased during the late swing phase (+20.9-37.3%; P < 0.05). CONCLUSION Running at a constant middle-distance pace led primarily to the fatigue of the plantarflexors with a compensatory increase in positive work done at the knee. Improving the fatigue resistance of the plantarflexors might be beneficial for middle-distance running performance.

Background Stand-to-sit (StandTS) movement is an important functional activity that can be challenging for older adults due to age-related changes in neuromotor control. Although trunk flexion, eccentric contraction of the rectus femoris (RF), and coordination of RF and biceps femoris (BF) muscles are important to the StandTS task, the effects of aging on these and related outcomes are not well studied. Research question What are the age-related differences in trunk flexion, lower extremity muscle activation patterns, and postural stability during a StandTS task and what is the relationship between these variables? Methods Ten younger and ten older healthy adults performed three StandTS trials at self-selected speeds. Outcomes included peak amplitude, peak timing, burst duration, and onset latency of electromyography (EMG) activity of the RF and BF muscles, trunk flexion angle and angular velocity, whole body center of mass (CoM) displacement, center of pressure (CoP) velocity, and ground reaction force (GRF). Results There were no age-related differences in weight-bearing symmetry, StandTS and trunk flexion angular velocity, or BF activity. In both groups, EMG peak timing of RF was preceded by BF. Compared to younger adults, older adults demonstrated shorter RF EMG burst duration, reduced trunk flexion, and reduced stability as indicated by the longer duration in which CoM was maintained beyond the posterior limit of base of support (BoS), greater mean anterior-posterior CoP velocity and larger standard deviation of CoM vertical acceleration during StandTS with smaller vertical GRF immediately prior to StandTS termination. Trunk flexion angle and RF EMG burst duration correlated with stability as measured by the duration in which the CoM stayed within the BoS. Significance Decreased trunk flexion and impaired eccentric control of the RF are associated with StandTS instability in aging and suggest the importance of including StandTS training as a part of a comprehensive balance intervention.

Whole-body vibration and muscle fatigue have both been shown to delay the trunk muscle reflex response and increase trunk muscle activation, leading to an increased risk of low back injuries. However, the effects of whole-body vibration on previously fatigued trunk muscles have never been tested, despite studies showing that prolonged exposure to whole-body vibration can lead to muscle fatigue. The purpose of this research was to investigate the effects of muscle fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration. The results showed that a fatigued muscle state resulted in increased muscle latency, muscle activation and perceived discomfort, which all escalate the risk of low back injuries. Additionally, the ISO 2631-1 comfort ratings did not increase with fatigue, showing a disconnect between these comfort ratings and the perceived discomfort ratings in a fatigued muscle state. Practitioner summary: When exposed to whole-body vibration, fatigued back muscles result in delayed muscle contraction, higher overall muscle activation and increased perceived discomfort, all of which are known to increase low back injury risk. ISO 2631-1 comfort ratings are unable to increase with fatigue, showing a disconnect with perceived discomfort ratings. Abbreviations: EMG: electromyography; EO: external oblique; IO: internal oblique; LE: lumbar erector spinae; LEO: left externaloblique; LIO: left internal oblique; LLE: left lumbar erector spinae; LTE: left thoracic erector spinae; MVC: maximum voluntarycontraction; REO: right external oblique; RIO: right internal oblique; RLE: right lumbar erector spinae; RTE: right thoracicerector spinae; SEAT: Seat Effective Amplitude Transmissibility; TE: thoracic erector spinae; WBV: whole body vibration.

There is a growing body of research examining the effects of plyometric jump training (PJT) on repeated sprint ability (RSA) in athletes. However, available studies produced conflicting findings and the literature has not yet been systematically reviewed. Therefore, the effects of PJT on RSA indices remain unclear. To explore the effects of PJT on RSA in athletes. Searches for this review were conducted in four databases. We included studies that satisfied the following criteria: (1) examined the effects of a PJT exercise intervention on measures of RSA; (2) included athletes as study participants, with no restriction for sport practiced, age or sex; and (3) included a control group. The random-effects model was used for the meta-analyses. The methodological quality of the included studies was assessed using the PEDro checklist. From 6367 search records initially identified, 13 studies with a total of 16 training groups (n = 198) and 13 control groups (n = 158) were eligible for meta-analysis. There was a significant effect of PJT on RSA best sprint (ES = 0.75; p = 0.002) and RSA mean sprint (ES = 0.36; p = 0.045) performance. We did not find a significant difference between control and PJT for RSA fatigue resistance (ES = 0.16; p = 0.401). The included studies were classified as being of “moderate” or “high” methodological quality. Among the 13 included studies, none reported injury or any other adverse events. PJT improves RSA best and mean performance in athletes, while there were no significant differences between control and PJT for RSA fatigue resistance. Improvements in RSA in response to PJT are likely due to neuro-mechanical factors (e.g., strength, muscle activation and coordination) that affect actual sprint performance rather than the ability to recover between sprinting efforts.

Over the past few years, energy drink consumption has increased among students aged 18–34 years. Energy drinks alter the balance, reduce blood flow and interfere with neuromuscular activation in the lower extremities. We attempted to determine which specific additive of three different drinks (red bull, rockstar, and bang) could contribute to changes in muscle activation of the ankle complex. Twenty healthy young adults aged 22–28 years were included in this study and allocated among 3 groups, red bull, rockstar, and bang. Neuromuscular data were obtained from EMG sensors positioned on the anterior tibialis and gastrocnemius before completing the four balance tasks. Each participant completed all the tasks before and after the 16-ounce Edrink. ANOVA was performed to compare the data before and after the beverage. Statistical significance was set at P

Agility is physically demanding and dogs encounter a considerable risk of injury during training and competition. Pre-performance warm-up is used routinely among human athletes to prepare the tissues for these physical demands, but in canine sports evidence for effects of warm-up is lacking. The aim of this study was to investigate the effects of warm-up in dogs on two major muscles involved in locomotion. It was hypothesised that, after warm-up, the muscles would be used more efficiently (more fibre resting time/total time), recruit fewer fibres (reduced spatial summation) and/or activated with a lower firing frequency (reduced temporal summation). The following factors ‘sex, age, weight, height, training level and agility experience’ were evaluated for their potential impact on muscle function parameters. Fourteen large (≥46 cm at the withers) agility dogs of different breeds and training levels performed a 5 min warm-up program three times, with a 2 min break between the programs for recording purposes. Acoustic myography sensors were attached on the skin over the muscles m. triceps brachii (TB) and m. gluteus superficialis (GS). Recordings of muscle activity were made, while the dogs trotted before warm-up and after each 5 min warm-up program. The dogs used TB more efficiently after 5 min (P

This study attempts to analyze the relationship between free-throw efficiency and the time of arm muscle activation in players from 3 basketball teams with different levels of experience was investigated. During the experiment each player made 20 free throws during which the activation time of his right and left biceps and triceps brachii muscles were measured with the use of surface electromyography and high-speed cameras. Significant differences in muscle activation time (t) during a free throw were found between the groups of basketball players (p = 0.038) (novices: t = 0.664 ± 0.225 s, intermediate-level players: t = 1.15 ± 0.146 s, experts: t = 1.01 ± 0.388 s). In the right triceps brachii muscle in expert basketball players the coefficient of variation (CV) amounted to 44.60% at 81% efficiency, and in novices to 27.12% at 53% efficiency. The time of arm muscle activation during a free throw and its fluctuations vary along with the training experience of basketball players. In all studied groups of players, the variability of muscle activation time in accurate free throws is greater than in inaccurate free throws. Free-throw speed is irrelevant for free-throw efficiency.

Background Movement dysfunctions are commonly reported in musicians, and in extreme cases may result in a persisting loss of motor control. This condition, whereby motor control of the hand during previously highly trained movements on the instrument is lost, is termed focal hand dystonia. It is widely considered to be a consequence of prolonged repetitive daily practice, often in combination with exposure to a range of other risk factors. Current literature recommends retraining as a promising treatment intervention, although only scant scientific evidence exists on which components should be included in a retraining program, and how these may be best administered. Methods A progressive muscle activation and movement exercise program was devised by one of the authors applying a series of anatomy-based off-instrument movement tasks. This series of fine motor control exercises, was used to both assess and retrain focal hand dystonia in a population of musicians. The standardized approach aimed to provide a systematic method of retraining musically relevant muscular synergies that could later be applied to the instrument, while still allowing individual modifications. Retraining sessions were mostly run online as a consequence of the coronavirus pandemic, although some early sessions were also able to be undertaken face to face. Both qualitative and quantitative measures were used in this case series to evaluate program efficacy, due to the typical heterogeneity of the focal hand dystonia participants. This included: blinded external neurological evaluation of video footage using the Tubiana grading system, written subjective feedback, exercise progressions, and performance outcomes. Results Pilot testing of 4 patients indicated the utility of the program over approximately a 12- month time period. All subjects improved, 2 of whom have returned to pre-dystonia performance levels. These patients reported the importance of patience and persistence with daily exercise sessions in their recovery. Conclusion Using off-instrument playing-relevant exercises to enhance fine motor control and muscle activation can be effective in retraining focal hand dystonia, regardless of additional treatments or level of performance. They should be regularly practiced and progressed in order for effects to be best progressed to instrumental applications. Further research may elucidate whether there are optimal outcomes with single or particular combinations of treatment approaches.

There have been very few studies involving swan motion during pilates exercises, and there is also insufficient scientific evidence to support the fact that Pilates swan motion strengthens specific muscles.Firstly, the purpose of this study was to evaluate the effect of 5 types Pilates swan motion (swan basic (SB), swan push-up (SP), swan holding posture (SH), form roller-based swan (SF), and circle-based swan (SC)) on muscle activity of deltoideus p. acromialis (DA), infraspinatus (IP), trapezius (TP), latissimus dorsi (LD), and erector spinae (ES). Secondly, the purpose of this study was to suggest an effective Pilates swan motion for strengthening muscle strength of each targeted muscle.Twenty-four healthy men in their 20s participated and all participants were measured muscle activity in DA, IP, TP, LD, and ES muscles by electromyography (EMG) during 5 Pilates swan motions (SB, SP, SH, SF,SC). The measured values were expressed as relative voluntary contraction (%RVC) values based on the SB.The %RVC values representing the muscle activity of DA and TP were significantly higher in SH and SP than in SC, SF, and SB (p .001). The %RVC values of IP and LD were significantly higher in SH and SC than in SF, SP, and SB (p .001). The %RVC value of ES was were significantly higher in SH than in SP, SC, SF, and SB (p .001).The application of SP, SC, and SH Pilates swan motion is an effective method to activate the back muscles of the trunk.

Summary Objectives The purpose of this study was to examine myoelectric activity, fatigue index and volume load adopting different intersession recovery periods between repeated resistance training (RT) bouts. Methods Fifteen recreationally-trained men participated in this study. Eight-repetition maximum (8RM) loads were determined for the bench press (BP) and 30° incline bench press (BP30) over two non-consecutive days. Three experimental protocols were performed in randomized order to examine the effect of different intersession recovery periods between repeated RT sessions for upper body muscles (pectoral major activity, anterior deltoid, triceps brachii, and biceps brachii) on volume load and myoelectric activity (SEMG), including: 24 hours (P24); 48 hours (P48); and 72 hours (P72). Each RT session consisted of performing four sets to failure for the BP and BP30 with 8-RM loads and 2-minute rest intervals between sets. Results The results showed that for SEMG activity, during the BP and BP30 exercises, there were no significant main effects for session, protocol, or interaction between protocols and sessions in the percentage difference between sets in activity of all muscles analyzed. Considering the overall session volume load, a significant main effect for session was noted. Volume load was significantly lower in Session 2 versus Session 1 under the P24 h protocol, without significant differences between the P48 and P72. Conclusion Therefore, coaches and practitioners who need to accomplish a higher volume load without negatively impacting fatigue index and myoelectric activity for upper body muscles, should adopt recovery periods longer than 24 hours between similar RT bouts.

Objective: To control the rate at which body weight drops, forefoot initiates floor contact with the limb relatively extended at each joint. However,...

The Nordic Hamstring Exercise (NHE) effectively strengthens the knee flexors. Typically conducted without assistance, extended knee angles are not reached with sustained muscle activation in the presence of insufficient eccentric strength and/or fatigue. This might impair the desired neuromuscular adaptations and assessment accuracy. This study investigated kinetic and kinematic differences between assisted and unassisted NHEs (3 × 3 repetitions) performed by sixteen male sprinters (22 years, 181 cm, 76 kg). Kinetic (peak moment, impulse) and kinematic parameters (e.g., time under tension, range of motion to excessive downward acceleration (ROM

Purpose: This study examined the effects of heel insoles on the static balance and leg muscle activity and posture control strategy dur ing external perturbation. Methods: Thirty healthy young men participated in the study. The subjects underwent two experimental conditions: 1) no heel insole condition (0cm) and 2) wearing heel insole condition (5cm). The static balance was measured using an I-Balance device, which measured the change in the center of gravity (COG). The onset time of muscle activation and muscle activation of the erector spinae (ES), ham string (HAM), gastrocnemius (GCM) were measured using surface EMG electrodes to determine the change in posture control strategy during external perturbation. Results: The speed and distance of COG were significantly higher in the wearing heel insoles condition than the no heel insole condition (p