Trapezius Muscle Activity Research Articles

Pitching Biomechanics and Shoulder Function in Baseball Pitchers with Scapular Dyskinesis.

The primary purpose was to investigate the influence of scapular dyskinesis (SD) on pitching biomechanics and shoulder function in high school baseball pitchers. The secondary purpose was to identify possible factors associated with shoulder function in pitchers with SD. Thirty-eight pitchers were classified into the SD group (n=26) or the non-SD group (n=12). They were evaluated with the Kerlan-Jobe Orthopaedic Clinic shoulder and elbow (KJOC) scale and clinical measurements of shoulder characteristics, and with measurements of scapular kinematics, muscle activation, and ball speed during fastball pitching. Compared to the controls, the pitchers with SD had less scapular external rotation (difference=11.3 degrees, ES=0.92, p=0.012) during overall pitching and less upper trapezius (UT) activation during the late cocking (difference=7.1%, ES=0.79, p=0.019) and acceleration phases (difference=12.5%, ES=0.75, p=0.035). Higher UT activation during the late cocking phase was significantly associated with higher KJOC scores (standardized β=0.415, p=0.039). In conclusion, deficits in scapular external rotation and decreased UT activation during pitching were found in pitchers with SD. Higher UT activation may be important for shoulder function in pitchers with SD.

A quantitative assessment of the effects of passive upper extremity exoskeletons on expert cardiovascular sonographers’ muscle activity and posture while performing transthoracic echocardiograms (TTE)

During scanning, sonographers often assume significant awkward postures which may lead to musculoskeletal pain and disability. Two exoskeletons were tested as an ergonomic intervention by sonographers during transthoracic echocardiograms (TTE). Four sonographers each performed TTEs using right- and left-handed scanning techniques, with and without two different passive upper extremity exoskeletons in two two-by-two experimental designs. Posture, muscle activity, and subjective discomfort scores were recorded. Of the two exoskeletons tested, the updated FLEX® design significantly reduced 10th percentile upper trapezius muscle activity during left hand scanning, while the AIRFRAME® did not impact muscle activity across all the muscles of interest. Furthermore, there was a slight decrease in the self-reported discomfort levels in their wrist and hands associated with performing TTE when wearing Exos1 compared to baseline. However, participants experienced issues with comfort, limitations on their range of motion (ROM), and interference with tasks with both exoskeletons. Collectively, the results indicate that the tested exoskeleton designs provide minimal benefit for reducing upper extremity muscle workload during TTE ultrasonography tasks.

A passive upper-limb exoskeleton reduced muscular loading during augmented reality interactions

The aim of this study was to evaluate a passive upper-limb exoskeleton as an ergonomic control to reduce the musculoskeletal load in the shoulders associated with augmented reality (AR) interactions. In a repeated-measures laboratory study, each of the 20 participants performed a series of AR tasks with and without a commercially-available upper-limb exoskeleton. During the AR tasks, muscle activity (anterior, middle, posterior deltoid, and upper trapezius), shoulder joint postures/moment, and self-reported discomfort were collected. The results showed that the exoskeleton significantly reduced muscle activity in the upper trapezius and deltoid muscle groups and self-reported discomfort. However, the shoulder postures and task performance measures were not affected by the exoskeleton during the AR interactions. Given the significant decrease in muscle activity and discomfort without compromising task performance, a passive exoskeleton can be an effective ergonomic control measure to reduce the risks of developing musculoskeletal discomfort or injuries in the shoulder regions.

The Effects of Scapular Stabilization Exercises Accompanied by Spine Stabilization Exercises Using An Unstable Surface on Muscle Activities for Subjects with Scapular Winging

This study was intended to inspect the influence of scapular stabilization exercises accompanied by spine stabilization exercises using an unstable surface on muscle activity in subjects with scapular winging. Thirty subjects with scapular winging participated in the experiment. The subjects were randomly divided into two groups. One group performed scapular stabilization exercises accompanied by spine stabilization exercises on an unstable surface, whereas the other group performed only scapular stabilization exercises. In order to study the influence of the intervention, the muscle activity around the shoulder was measured. According to the experimental results, the activation of the lower trapezius muscle and serratus anterior muscle increased significantly in both groups after intervention. The muscle activities of the lower trapezius and serratus anterior in the control group were not as high as those in the experimental group. Moreover, the muscle activities of upper trapezius and pectoralis major decreased significantly in both groups after the exercise interventions, but no significant difference was observed between the two groups. As a result, the scapular stabilization exercises that are widely used in clinical practice were shown to increase lower trapezius and serratus anterior activities. Moreover, a combination of such exercises with spine stabilization exercises on an unstable surface was shown to confer greater benefits than scapular stabilization exercises alone and is thus recommended.

Trunk muscle activation in side plank exercises with and without external-focus instruction

BACKGROUND: Trunk muscle activity during isometric exercise is altered by external-focus instruction. OBJECTIVE: To check alterations in trunk muscle activity during side plank exercise both with and without instructions to refrain from crushing an item (external-focus instruction method). METHODS: Twenty-one healthy men aged 20–49 participated in this study. Ten trunk muscle activities were measured using surface electromyography during side plank exercises both with and without external-focus instruction. The unpaired t-test or Mann–Whitney U test was used to compare differences between exercise tasks and between sides. RESULTS: Side plank exercise with external-focus instruction increased activity of the upper trapezius, lower trapezius, latissimus dorsi, medial head of the triceps, and internal oblique on the supported side when compared with that without external-focus instruction (p< 0.05 for all). On the unsupported side, side plank exercise with external-focus instruction significantly increased activity of the upper trapezius, lower trapezius, latissimus dorsi, medial head of the triceps, clavicular part of the pectoralis major serratus anterior, external oblique, rectus abdominis, internal oblique, and multifidus when compared with that without external-focus instruction (p< 0.001 for all). CONCLUSIONS: Adding the external-focus instruction method to the conventional side plank exercise may be effective in increasing the trunk muscles’ activity.

Effects of anti-fatigue lenses on performance, muscle activity and subjective discomfort responses during a seated computer task

Anti-fatigue lenses (AFL) intend to provide health benefits in association with computer work. Their effects on visual and muscle discomfort mechanisms and task performance remain unclear. Twenty-three computer users (n = 12 males) underwent two 90-min computer sessions with AFL or placebo lenses. Eye strain, body discomfort, typing performance, upper trapezius (UT) activation amplitude and variability, and neck posture were analyzed for time, condition, and sex effects. No significant effects of condition were observed on the dependent measures evaluated. Discomfort increased over time (neck/shoulder: p < .001), more so in females (eye strain: p < .001). Females’ UT activation amplitude was negatively correlated to eye strain in the placebo condition (p = .05).

스마트 자동차 좌석을 이용한 엉덩이의 동적 균형조절이 코어 등근육 활성도에 미치는 효과

Sitting in a car seat for a long time causes fatigue in muscles such as trapezius and paraspinal muscles, which increases muscle fatigue and tension and eventually causes in degenerative spinal changes and pain. Therefore, the authors attempt to investigate the effect of trapezius and lower back muscle activity changes on whether fatigue may be improved by balancing the buttock contact pressure in the sitting position. The purpose of this study was to assess the electrophysiologic effect of dynamic balance control for the trapezius and lower core back muscles through wireless surface electromyographic evaluation using the smart car seat equipped with an ICT-based air bladder. Surface electromyography (sEMG) was measured for each 32 participant’s trapezius and lumbar back muscles in three phases: 1) initial on standing, 2) seated for 25 minutes without balancing ischial pressure, 3) seated for 25 minutes with balancing ischial pressure, and then sEMG was measured for 1 minute on the standing of three individual phases. In the trapezius and low back muscles, the sEMG value of the three-phase MVIC showed a statistically significant increase in the left side compared to the right side (p0.0001). % MVIC difference increased in unbalanced seating (7.32±0.83) compared to the initial measure (7.24±1.72). However, it decreased with balancing seating(6.73±1.81, p=0.049). There was no statistically significant difference in the overall %MVIC differences between both lower back muscles among three phases (p=0.35), but the balanced seating showed a slightly increased % MVIC difference (p=0.10) in contrast to that of the trapezius. Balanced control of hip pressure using automatic logic control of ICT-based smart car seats has the effect of reducing the left-right difference in muscle activity of upper core muscles compared to that of non-balanced seating. Conclusively, it is believed that the difference in the left and right imbalances in the activity of trapezius can be alleviated through the pressure balance seating at the driver’s seat, and the effect of improving muscle fatigue can be expected. Nevertheless, driving in a sitting position, regardless of balance control, the lower core muscles continue to increase the activity of the lumbar muscles, which inevitably causes pain, discomfort, and fatigue over time. Wireless bio-sensing and balanced seat control using ICT-integrated smart car seats can be used as important application science fields that can improve muscle fatigue and degenerative spinal changes associated with professional workers.

Alteration of muscle activity during voluntary rehabilitation training with single-joint Hybrid Assistive Limb (HAL) in patients with shoulder elevation dysfunction from cervical origin.

Shoulder elevation, defined here as arm raising, being essential for activities of daily living, dysfunctions represent a substantial burden in patients' lives. Owing to the complexity of the shoulder joint, the tightly coordinated muscular activity is a fundamental component, and neuromuscular impairments have devastating effects. A single-joint shoulder type version of the Hybrid Assistive Limb (HAL) allowing motion assistance based on the intention of the user via myoelectric activation has recently been developed, and its safety was demonstrated for shoulder rehabilitation. Yet, little is known about the physiological effects of the device. This study aims to monitor the changes in muscle activity and motion during shoulder HAL rehabilitation in several patients suffering from shoulder elevation dysfunction from cervical radicular origin. 8 patients (6 males, 2 females, mean age 62.4 ± 9.3 years old) with weakness of the deltoid muscle resulting from a damage to the C5 nerve root underwent HAL-assisted rehabilitation. We combined surface electromyography and three-dimensional motion capture to record muscular activity and kinematics. All participants showed functional recovery, with improvements in their Manual Muscle Testing (MMT) scores and range of motion (ROM). During training, HAL decreased the activity of deltoid and trapezius, significantly more for the latter, as well as the coactivation of both muscles. We also report a reduction of the characteristic shrugging compensatory motion which is an obstacle to functional recovery. This reduction was notably demonstrated by a stronger reliance on the deltoid rather than the trapezius, indicating a muscle coordination tending toward a pattern similar to healthy individuals. Altogether, the results of the evaluation of motion and muscular changes hint toward a functional recovery in acute, and chronic shoulder impairments from cervical radicular origin following shoulder HAL rehabilitation training and provide information on the physiological effect of the device.

Effects of Upper Trapezius Myofascial Trigger Points on Scapular Kinematics and Muscle Activation in Overhead Athletes.

Prolonged overactivity of the upper trapezius muscle with myofascial trigger points might cause muscle fatigue and subsequently change scapular kinematics and associated muscular activities. Scapular kinematics and associated muscular activities were investigated in 17 overhead athletes with upper trapezius myofascial trigger points and 17 controls before and after a fatigue task. Participants performed a fatigue task requiring sustained isometric scapular elevation. The outcomes included scapular kinematics (upward/downward rotation, external/internal rotation, posterior/anterior tilt) that were tracked by the Polhemus FASTRAK (Polhemus Inc., Colchester, VT, USA) system with Motion Monitor software and muscular activities (upper trapezius, lower trapezius and serratus anterior) that were collected at 1000 Hz per channel using a 16-bit analog-to-digital converter (Model MP 150, Biopac systems Inc., CA, USA) with pairs of silver chloride circular surface electrodes (The Ludlow Company LP, Chocopee, MA) during arm elevation. Mixed ANOVAs were conducted to characterize the outcomes with and without a fatigue task in participants with myofascial trigger points. Decreased scapular posterior tipping during 90 degrees of arm raising/lowering (effect sizes of 0.51 and 0.59) was likely to be elicited by the scapular elevation fatigue task in the presence of myofascial trigger points. Activity of the lower trapezius was higher in the myofascial trigger point group (6.2%, p = 0.036) than in the control group. Following the fatigue task, both groups showed increased activity in the upper trapezius (9.0%, p = 0.009) during arm lowering and in the lower trapezius (2.7%, p < 0.01) during arm raising and lowering. Decreased scapular posterior tipping during 90 degrees of arm raising/lowering after a fatigue task may lead to impingement. We found that the presence of upper trapezius myofascial trigger points in amateur overhead athletes was related to impaired scapular kinematics and associated muscular activities during arm elevation after a fatigue task, especially the decreased scapular tipping during 90 degrees of raising/lowering.

Acute, Non-Specific Low Back Pain Does Not Impair Isometric Deadlift Force or Electromyographic Excitation: A Cross-Sectional Study.

Low back pain (LBP) is a leading cause of disability. The use of deadlift-based assessments in assessing LBP is becoming common in clinical settings, but these concepts have not been well studied. We sought to compare force and muscle excitation during isometric deadlifts in participants suffering from LBP versus asymptomatic controls. We also compared these outcomes for conventional versus hexagonal barbells. Sixteen adults with mild-to-moderate, acute, non-specific LBP and 19 controls performed maximal, isometric deadlifts while standing on a force plate using conventional and hexagonal barbells. Surface electromyographic signals were recorded from the upper trapezius, external oblique, erector spinae, vastus lateralis, and biceps femoris. Normalized peak force and peak rate of force development were similar for those with acute, non-specific LBP and controls. Surface electromyographic excitation was not different between groups, but was higher with the hexagonal barbell for the vastus lateralis and upper trapezius. Both groups felt equally safe and confident. In summary, the presence of acute, non-specific LBP did not impair peak and rapid force or muscle excitation. Hexagonal barbells may optimize knee extensor and trapezius activation. Deadlift-based force assessments appear safe and may be useful in the assessment of functional strength in patients with acute, non-specific LBP.

Optimal bipolar system positioning to provide information about the trapezius activity associated with scapular retraction during shoulder exercises for resistance training

Objective. Recently, the use of EMG biofeedback to make subjects aware of the stabilizer activation associated with scapular retraction during exercise has been of interest, and challenges related to EMG detection have been addressed. Whether there is an optimal bipolar positioning that discriminates the stabilizer activation with retraction from a neutral scapular position during resistance exercises is an open issue that we address here by simultaneously mapping different positions using high-density surface electromyography (HD-sEMG). Approach. Sixteen resistance-trained males performed five pulling exercises with and without scapular retraction, namely barbell rows, dumbbell rows, pull-downs at a lat machine, seated rows, and TRX (total resistance exercises) system rows. HD-sEMG was acquired in a monopolar mode from the medial and lower trapezius (8 × 4 electrodes and inter-electrode distance (ied): 10 mm) and different bipolar systems were simulated in terms of positioning, interelectrode distance, and orientation with respect to the spine: longitudinal with three ieds (20 mm, 30 mm, and 40 mm), one transversal, and two diagonals (ied: 20 mm), totalling six EMG sets. To identify the optimal electrode pair that was able to distinguish between the presence or absence of scapular retraction, we computed: (i) the root mean square (RMS) map for each condition and the difference between them, obtaining a differential RMS map per subject; and (ii) the intersection of cumulative maps, by summing the differential (binary) maps from all subjects. Main results. For the lower trapezius, the results revealed that the diagonal direction (45 degrees; ied: 20 mm) obtained the greater occurrence of intersecting segments within and between exercises than the other electrode configurations, showing low variability for the optimal positioning across exercises. Electrode configuration varied within and between the pulling exercises for the medial trapezius. Significance. This study allows us to identify an optimal bipolar positioning (consistent across subjects and exercises) for lower trapezius activity assessment, representing a guideline for electrode positioning when EMG biofeedback is adopted for selective activation of the lower trapezius during pulling exercises.

The Effect of Modified Push-up Exercise Using Electromyography Biofeedback on Selection of Scapular Stabilizing Muscles

Background: The serratus anterior (SA) muscle is an important scapular stabilizer and has a profound role in retaining the scapulohumeral rhythm. Therefore, modified push-up plus (MPUP) has been advised to strengthen this muscle as a closed chain workout. However, few previous studies have reported the possibility of a reparative motion from pectoralis major (PM) that could replace and amend SA's function during push-up plus. Objectives: The current study examined MPUP's effect using biofeedback EMG on some of the selected scapular stabilizers. Methods: Sixteen healthy young subjects voluntarily participated in this study. Each subject performed push-ups, from the quadruped position, under two conditions (i.e., with or without visual and auditory biofeedback). Surface EMG measured pectoralis major, serratus anterior, and upper trapezius activity. A paired t-test was used to determine any statistically significant difference between the two conditions. Additionally, the effect size was calculated to quantify the magnitude of EMG biofeedback in each muscle. Results: MPUP training using biofeedback significantly increased SA muscle activity and decreased PM muscle activity, but there was no significant change in UT activity. Conclusions: Excessive PM activity was repressed because of biofeedback, and the workout was done with the enhancement of SA muscular activity. Thus, including biofeedback while doing MPUPs helps limit PM's supplementary action and enhance SA muscle activity.

Effects of hanger reflex on the cervical muscular activation and function: A surface electromyography assessment.

Introduction: Cervical muscular dysfunction is closely associated with disorders and neuromuscular diseases of the cervical spine, and the hanger reflex (HR) has the potential to become a rehabilitation method. The muscular electrophysiology mechanism of HR is unclear. This study aims to identify the impacts of HR on cervical rotators’ myoelectrical activity and function. Methods: We designed a self-control clinical trial, and asymptomatic volunteers were continuously included from 1 September 2021 to 30 April 2022 in our department. Rotation tasks were performed on both sides under each of the situations: no HR, unilateral HR, and bilateral HR. Surface electromyography (SEMG) was used to detect the myoelectrical activity of agonistic splenius capitis (SPL), upper trapezius (UTr), and sternocleidomastoid (SCM). The co-contraction ratio (CCR) during rotation tasks was calculated. Correlation analyses and multiple linear regression were performed. Results: Finally, 90 subjects were enrolled (power >90%). The adjusted EMG value (aEMG) of SPL UTr, SCM, and rotating CCR under the unilateral HR and bilateral HR were higher than no HR; the aEMG of SPL and rotating CCR under the bilateral HR were higher than the unilateral HR. Multiple linear regression showed that HR pattern and age were the independent affecting factors for the aEMG of SPL (p < 0.001, p < 0.001), UTr (p < 0.001, p < 0.001), and SCM (p < 0.001, p < 0.001); BMI was an independent affecting factor for the aEMG of SPL (p < 0.001) and SCM (p < 0.001); HR pattern was the only affecting factor for CCR (p < 0.001). Conclusion: HR can increase the cervical rotators’ myoelectrical activities and rotating CCR, and the effects of bilateral HR are greater than unilateral HR, suggesting that bilateral HR has a greater clinical potential to become a rehabilitation method for treating cervical neuromuscular disorders.

Changes in electromyographic activity of latent trigger points after a dry needling intervention: a randomised controlled trial

ObjectiveTo analyse the effects of dry needling (DN) in upper trapezius latent trigger points (LTrPs) on pressure pain threshold (PPT) and surface electromyography (sEMG). DesignRandomized, double-blind, placebo controlled clinical trial. SettingsSports Rehabilitation Laboratory, University of Castilla-La Mancha. ParticipantsForty-six participants (18–35 years old) with LTrP in the upper trapezius were divided into two groups: DN-group and Sham-DN-group. InterventionsIn the DN-group, the needle was inserted 10-times through the skin, and it was manipulated up and down using a "fast in and out" technique. In the Sham-DN-group, non-penetrating needles were used. Main outcome measuresPPT, sEMG at rest, and sEMG in isometric contraction of the LTrP of the upper trapezius muscle were evaluated at baseline, 30 min after treatment, and after 24 h, and 72 h of follow-up. ResultsThe mean change in sEMG at rest between baseline and 30 min was − 0.38 (0.38) %refRMS for the DN group and − 0.05 (0.31) %refRMS for the Sham-DN group (mean difference −0.34, 95% confidence interval (CI) of the difference: − 0.54 to − 0.13), and between baseline and 24 h was − 0.35 (0.35) %refRMS for the DN group and − 0.06 (0.58) %refRMS for the Sham-DN group (mean difference −0.29, 95% CI: −0.57 to −0.01). In addition, the DN-group showed higher values of PPT than the Sham-DN group at 72 h (5.22 (1.23) to 4.65 (1.03) kg/cm2; p < 0.05). ConclusionsA single session of DN intervention was effective in reducing the electromyographic activity, muscle fatigue and pain of the upper trapezius muscle in LTrP. Contribution of paperIn healthy volunteers dry needling is effective:•for reducing electromyography activity in latent trigger points.•for reducing muscle fatigue in latent trigger points.•in increasing pressure pain threshold in latent trigger points.

Upper Body Muscle Activation And Measures Of Sprint Performance

PURPOSE: Effective arm swing and core muscle activation are involved in acceleration and maximal sprinting, yet muscle activity in these areas have not been measured via electromyography (EMG) during over ground sprinting trials. The purpose of this study was to explore the relationship between muscle activation of the upper body and measures of performance during sprint acceleration and maximal sprinting. METHODS: Sixteen participants (20.93 ± 0.96 yrs.; 1.71 ± 0.07 m; 67.69 ± 11.81 kg) completed six 40-m sprint trials on an outdoor track, with three from a block start and three from a split start. Muscle activation was measured via EMG in the triceps brachii, biceps brachii, upper trapezius, anterior deltoid, latissimus dorsi, erector spinae, rectus abdominis, and oblique muscles, recorded as a percentage of maximal voluntary isometric contraction. Split times recorded during each sprint were used to calculate acceleration, net horizontal force (Fh), and the ratio of Fh and resultant ground reaction force (%RF) using previously validated methods. Repeated measures multilevel modeling was used to evaluate the relationship between mean upper body muscle activation and average acceleration, Fh, and %RF during each 10-m window of the sprint. RESULTS: During the 0-10 m window, mean activation of the upper trapezius showed a significant positive relationship with acceleration (t = 2.66, p = 0.01), Fh (t = 2.20, p = 0.03), and %RF (t = 2.57, p = 0.01), erector spinae activation was positively associated with %RF (t = 2.42, p = 0.02), and biceps activation was negatively associated with Fh (t = -2.23, p = 0.03). In the 30-40 m window, there was a significant negative relationship between mean latissimus dorsi activation and %RF (t = -2.16, p = 0.04). There were no significant relationships between upper body muscle activation and indicators of sprint performance detected during the 10-20 m or 20-30 m windows. CONCLUSIONS: These results indicate that upper trapezius muscle activity is important during initial sprint acceleration, which agrees with past research on scapular restriction limiting maximal acceleration while sprinting. After the initial period of sprint acceleration, there was no evidence that greater activation of certain upper body muscles was related to improving maximal sprinting performance.

Scapular movement training is not superior to standardized exercises in the treatment of individuals with chronic shoulder pain and scapular dyskinesis: randomized controlled trial

Purpose To investigate whether scapular movement training (SMT) is superior to standardized exercises in improving scapular biomechanics, behavioral, and clinical aspects of individuals with shoulder pain. Methods and methods A total of 64 individuals with chronic shoulder pain were randomly assigned to receive 16 sessions of SMT or SE over 8 weeks. Outcome measures included three-dimensional scapular kinematics, muscle activity of scapulothoracic muscles, pain, disability, fear-avoidance, kinesiophobia, and self-perceived changes. Kinematics and muscle activity were assessed at baseline and after treatment, and self-reported measurements at baseline, 4, 8, and 12 weeks. Results SMT significantly (p < 0.05) decreased scapular internal rotation during arm elevation and lowering at sagittal and scapular planes (mean difference [MD]: ranged from 2.8 to 4.1°), and at lower angles of arm elevation and lowering at the frontal plane (MD: 3.4° and 2.4°, respectively), increased upper trapezius (UT) activity (MD: 10.3%) and decreased middle trapezius (MT) (MD: 60.4%) and serratus anterior (MD: 9.9%) activity during arm lowering compared to SE. Both groups significantly improved pain, disability, fear-avoidance, kinesiophobia, and self-perceived changes over 4 weeks, which was sustained over the remaining 8 weeks. Conclusions SMT is not superior to standardized exercises in improving scapular biomechanics, behavioral, and clinical aspects of individuals with shoulder pain. Clinical trial registration number NCT03528499 Implications for rehabilitation Scapular movement training (SMT) showed small and likely not clinically relevant changes in scapular kinematics and muscle activity compared to standardized exercises. SMT and standardized exercises presented similar improvements in pain, disability, fear-avoidance beliefs, kinesiophobia, and self-perceived change in health condition immediately following 4-weeks of treatment, which was sustained over the following 8 weeks. The changes in patient-reported outcome measures are unlikely to be associated with changes in scapular kinematics and electromyographic activity. Clinicians should consider other factors than scapular movement during the treatment of patients with shoulder pain.

P16. Biomechanical assessments of the spine during a 2000M ergometer row test

<h3>BACKGROUND CONTEXT</h3> Ergometer rowing has gained popularity as a "low-impact" form of exercise. Lumbar spine injuries are the most common injury in rowers. Previous studies have shown ergometer training to be associated with an increased risk of injury. Muscular fatigue and spine range of motion may correlate to pain or injury in ergometer rowing. <h3>PURPOSE</h3> The purpose of the present study is to utilize 3D motion capture and electromyography (EMG) assessments to 1) evaluate how muscular activation relates to lumbar spine mechanics; 2) determine the impact of fatigue on back muscle activation and biomechanics. <h3>STUDY DESIGN/SETTING</h3> Prospective analysis. <h3>PATIENT SAMPLE</h3> Seventeen rowers (M=8, F=9) with a mean age of 38 ± 9.1 years and a VO2 max of 44.4 ± 7.8 ml·kg·min-1. <h3>OUTCOME MEASURES</h3> Pull force, kinematics and muscle activation were recorded at 200m, 600m, 1000m, 1400m and 1800m distances. Spine flexion (degrees) was investigated. <h3>METHODS</h3> Seventeen rowers (m=8, F=9; age=38±9.1 years, VO2max=44.4±7.8 ml·kg·min-1) participated and performed a 2000-meter row on an ergometer. Pull force, kinematics and muscle activation were recorded using a load cell, motion capture system and a wireless EMG, respectfully. Data was recorded at 200m, 600m, 1000m, 1400m and 1800m distances. Spine flexion was calculated at three points in the sagittal plane and labeled as upper-, mid- and lower-spine. A mixed-model ANOVA repeated on row distance and a Tukey's post-hoc test was used to compare biomechanical assessments. Type-I error was set at a=0.05. <h3>RESULTS</h3> Average time to complete the test was 8.4 ± 1.0 min. Trapezius and mid-spinal erector activation was maintained through the row. A steady decrease in mean and peak latissimus dorsi activation was observed with increasing distance (p < 0.05), paired with an increase in peak lumbar spinal erector activation (p < 0.05), indicating fatigue of the upper back musculature followed by compensatory reliance on low back muscles to maintain/increase force. Upper spinal flexion (min and max) increased by 1000m, indicating an increase in the overall state of flexion with progressing distance (p < 0.05). Mid-spinal flexion demonstrated increased min flexion (indicating reduced peak extension) beginning at 1400m (P < 0.05). Lumbar spine flexion was maintained throughout the row, indicating that the primary mechanics fatigue change was a result of upper back rounding due to upper back muscle fatigue. Results indicate that low back pain and injuries associated with rowing may not be because of altered flexion/extension of the lumbar spine but rather, a result of increased workload placed on low back musculature to compensate fatiguing muscles and changes in the row mechanics of the upper and mid spine. Although ergometer rowing is often considered "low-impact," given the high number of contractions over a short time (<10min), it may be advisable for rowers to avoid multiple days of fatiguing row ergometer training per week. <h3>CONCLUSIONS</h3> The present findings will provide greater insight into the potential mechanisms of fatigue during ergometer rowing. Results will also give medical professionals a better understanding of the origins and presentation of soft tissue injuries in the spine in recreational rowers. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Investigation of precision task demands on workers' muscular activities, heart rate, and perceived exertion rating.

Manual material handling (MMH) tasks significantly contribute to musculoskeletal disorders in manual workers. In this study, we assessed the physical factors of precision lifting tasks that affect muscular activities (electromyography, EMGs), heart rate, and perceived exertion rating in ten healthy male workers aged 25-35 years, while considering the safety aspect of the common types of safety footwear. The independent variables that were assessed are as follows: 1) lifting method (precise and inexact), 2) lifting frequency (one and four liftings/min), and 3) type of safety footwear worn by the worker (light, medium, or heavy). The response variables data, represented by EMG signals, for four muscular activities (biceps brachii, deltoid, trapezius, and erector spinae), heart rate, and perceived exertion were analyzed using a three-factor within-subjects design. The results showed that wearing heavy safety shoes increases the effort used with precise lifting methods in trapezius and erector spinae muscular activities. We also observed that the heart rate and perceived exertion increased rapidly at four lifts/min compared to one lift/min, regardless of the lifting method. The advantages of choosing appropriate safety footwear must be carefully assessed before replacing the conventional working safety shoes.

The influence of idiopathic chronic neck pain on upper trapezius and sternocleidomastoid muscle activity and elasticity during functional reaching: A cross-sectional study

It remains unclear whether idiopathic chronic neck pain is associated with changes in muscle stiffness alongside alterations in neuromuscular control. Therefore, the purpose of this study was to determine the influence of idiopathic chronic neck pain on the muscle stiffness and muscle activity of the upper trapezius and sternocleidomastoid muscles during the maintenance of unilateral and bilateral functional reaching tasks. Surface electromyography (EMG) and ultrasound shear wave elastography were collected from the sternocleidomastoid and upper trapezius muscles in 18 individuals with idiopathic chronic neck pain and 18 matched healthy controls. Participants completed three functional reaching tasks; 1) unilateral forward reach, 2) bilateral forward reach, and 3) unilateral upward reach, and held at the top of each reaching movement for data to be collected bilaterally. A univariate ANOVA was utilized for each outcome measure (mean EMG amplitude and shear wave velocity) and each reaching task. Individuals with idiopathic chronic neck pain exhibited significantly lower upper trapezius activation during bilateral reaches without corresponding changes to stiffness during similar trials. Similarly, this cohort exhibited decreased sternocleidomastoid stiffness during forward reaching, without corresponding activation changes. Lastly, women demonstrated consistently higher sternocleidomastoid activation and stiffness when compared to men. These findings indicate individuals with idiopathic chronic neck pain may adapt their movement strategies, possibly for pain avoidance. The demonstrated changes in muscle stiffness independent of changes in muscle activity highlight the importance of evaluating both muscle stiffness and activation in individuals with idiopathic chronic neck pain prior to designing rehabilitation programs.

Immediate Effects of Cervical Spine Manipulation Compared With Muscle Energy Technique on Neck Muscle Activity and Range of Motion in Asymptomatic Participants: A Randomized Study

ObjectiveThe purpose of this study was to investigate the immediate effects of cervical spine manipulation (SM) compared with muscle energy technique (MET) on neck muscle activity and range of motion in asymptomatic people. MethodsA randomized parallel-group study was conducted at a chiropractic teaching clinic in Durban, South Africa. Fifty asymptomatic participants between 18 and 35 years of age were randomly assigned into group 1 or group 2. Group 1 received cervical SM, and group 2 received MET. Participants were blinded to group allocation only. Baseline and post-test measurements consisted of resting upper trapezius and posterior cervical muscle activity and cervical spine range of motion (ROM) in lateral flexion and extension. ResultsA significant difference was found in cervical ROM within groups (P < .001), with no significant difference observed between the 2 groups. The right posterior cervical muscles showed a significant difference in group 1 only (P = .012). No significant muscle activity changes occurred in group 2. Resting muscle activity measures showed no statistically significant changes between groups. ConclusionA single application of SM and MET to the cervical spine immediately increased cervical ROM. Neither cervical SM nor MET changed resting posterior cervical and upper trapezius muscle activity.