Trapezius Muscle Activity Research Articles

Effect of Periodic Voluntary Interventions on Trapezius Activation and Fatigue During Light Upper Limb Activity.

The effects of diverse periodic interventions on trapezius muscle fatigue and activity during a full day of computer work were investigated. Musculoskeletal disorders, including trapezius myalgia, may be associated with repeated exposure to prolonged low-level activity, even during light upper-extremity tasks including computer work. Thirty healthy adults participated in a study that simulated two 6-hour workdays of computer work. One workday involved imposed periodic passive and active interventions aimed at disrupting trapezius contraction monotony (Intervention day), whereas the other workday did not (Control day). Trapezius muscle activity was quantified by the 3-dimensional acceleration of the jolt movement of the acromion produced by electrically induced muscle twitches. The spatio-temporal distribution of trapezius activity was measured through high-density surface electromyography (HD-EMG). The twitch acceleration magnitude in one direction was significantly different across measurement periods (p = 0.0156) on Control day, whereas no significant differences in any direction were observed (p > 0.05) on Intervention day. The HD-EMG from Intervention day showed that only significant voluntary muscle contractions (swing arms, Jacobson maneuver) induced a decrease in the muscle activation time and an increase in the spatial muscle activation areas (p < 0.01). Disruption of trapezius monotonous activity via brief voluntary contractions effectively modified the ensuing contraction pattern (twitch acceleration along one axis, active epochs reduction, and larger spatial distribution). The observed changes support an associated reduction of muscle fatigue. This study suggests that disruptive intervention activity is efficient in reducing the impact of trapezius muscle fatigue.

Muscle Activation of Serratus Anterior during Self-Resisted Scapular Protraction with Forward Flexion on Unstable Surface in Sitting Position

Background The muscle activation of the serratus anterior (SA) is important for the performance of glenohumeral joint during functional activities. However, little research in comparison of SA muscle activation during self-resisted scapular protraction exercises in forward flexion of shoulder has been reported. Purpose The purpose of this study was to compare muscle activity of SA during three different scapular protraction exercises according to various conditions [Forward flexion with protraction (FFP), FFP with self-resistance (FFPS), FFPS with hand-exerciser (FFPSH)] in healthy individuals in sitting position. Study design Comparative, repeated measures design Methods Twenty subjects were participated. The muscle activity of SA, upper trapezius (UT) and pectoralis major (PM) were measured by using a surface electromyography device. Each subject was asked to perform three different scapular protraction exercises (FFP vs. FFPS vs. FFPSH) in random order. One-way repeated measures analysis of the variance and a Bonferroni post hoc test were used. The level of statistical significance was set at α=0.01. Results The muscle activity of SA and the SA/UT ratio were significantly different among three conditions (FFP vs. FFPS vs. FFPSH) (<italic>p</italic>&lt;0.01). The muscle activity of SA and the SA/UT ratio during FFPSH were significantly greater compared to those with FFP and FFPS (<italic>p</italic>&lt;0.01). However, the SA/PM ratio was not significantly different among three conditions (<italic>p</italic>&gt;0.05). Conclusions FFPSH exercise for facilitation of SA muscle can be recommended.

Muscle Activity Before and After Subacromial Injection.

Shoulder muscle activation in patients with subacromial impingement is highly cited and variable in the literature. Differences between studies could be due to artifacts introduced by normalization practices in the presence of pain. Ultimately, this lack of knowledge pertaining to pathogenesis limits the clinical treatment and restoration of muscular function. A total of 21 patients with stage 2 subacromial impingement and 21 matched controls were recruited for EMG testing of their affected shoulder during an arm elevation task. The patients were tested before and after receiving an injection to their subacromial bursa. The EMG from 7 shoulder muscles were measured before and after treatment during humeral motion in the scapular plane. Our findings indicate an increase in anterior deltoid, middle deltoid, and upper trapezius activity following the injection; further, this trend extended to the controls. The control subjects had a greater activation of the latissimus dorsi at peak arm elevation when compared with the patient group postinjection. Our results indicate that a reduction in subacromial pain is associated with changes in shoulder muscle recruitment, primarily of the deltoid. This change in deltoid activity may lend evidence to rotator cuff function in patients without rotator cuff tears.

The Influence of Neuroticism on the Muscle Response in the Trapezius and Frontalis Muscles to Anticipatory Stress

Abstract. Objective quantification of mental stress in the workplace would be beneficial for designing work tasks to avoid the negative consequences of mental stress. Methods such as surface electromyography have proven to be sensitive to mental demands. However, there is little knowledge about the muscle response and moderating factors during anticipatory stress paradigms. This study examined whether the personality dimension neuroticism moderates the muscle response to the expectation of an unpredictable electrical shock. Forty-seven subjects underwent three expectation phases, in which they could expect a pleasant audio signal (NoShock) or an electric shock in two conditions (anticipation of the first: Shock1, and second electric shock: Shock2) at an unpredictable moment. The frontalis muscle activity and the upper and upper/middle parts of the trapezius muscle were recorded using surface electromyography. Neuroticism was surveyed using the Big Five Inventory to assign the subjects to a group with lower or higher neuroticism. Shock1 only induced higher trapezius muscle activity in the higher neuroticism group, which vanished during Shock2, while the frontalis muscle showed no significant effects. The results suggest that neuroticism should be considered a moderating factor in assessing anticipatory stress using surface electromyography at the trapezius muscle.

Machine learning methods for electromyography error detection in field research: An application in full-shift field assessment of shoulder muscle activity in apple harvesting workers

This study presented an alternative technique for processing electromyography (EMG) data with sporadic errors due to challenges associated with the field collection of EMG data. The application of this technique was used to detect errors, clean and optimize EMG data in order characterize and compare shoulder muscular load in farmworkers during apple harvesting in a trellised orchard. Surface EMG was used to take measurements from twenty-four participants in an actual field work environment. Anomalies in the EMG data were detected and removed with a customized algorithm using principal component analysis, interquartile range cut-off and unsupervised cluster analysis. This study found significantly greater upper trapezius muscle activity in farmworkers who used a ladder as compared to the alternative platform-based method where a team of mobile platform workers harvested apples from the tree tops and a second separate team of ground workers harvested apples from the tree bottoms. By comparing the unprocessed and the processed, anomaly-free EMG data, the robustness of our proposed method was demonstrated.

Effects of Trunk Postures and Shoulder Flexion Angles on the Muscular Activity of Scapular Upward Rotators

The forward bending posture is a risk factor that can cause musculoskeletal injury for workers working in industry. Previous studies have been largely concerned with examining the effects of turtle neck, slouched posture, and kyphosis on the scapular upward rotators. However, no studies have investigated the effect of forward bending of the trunk on the scapular upward rotators to date. The purpose of this study was to investigate the effect of forward tilting of the trunk and the shoulder flexion angle on the muscular activity of the Upper trapezius. The participant population comprised of 10 male adults and 20 shoulders in total were assessed. To begin with, EMG electrodes were attached to the upper trapezius muscles. The participants were instructed to perform isometric shoulder flexion at 120° angles in upright standing and forward bending postures. The muscle activity was measured by surface electromyography to obtain a root mean square value and was expressed as a percentage of the mean maximal voluntary isometric contraction (%MVIC). A paired t-test was used to determine the changes in muscle activity according to trunk posture and a shoulder flexion angle. A paired t-test was performed at α=.05. The result of Significant main effect for trunk posture was found for the upper trapezius muscles(p<.05). Additionally, a significant main effect for shoulder flexion angle was revealed in the upper trapezius muscles(p<.05). The results demonstrate that forward bending of the trunk may increase the activity of the upper trapezius. Therefore, industrial workers who manifest hyperactivation of the upper trapezius should maintain upright trunk posture while working.

Effects of Intended Scapular Posterior Tilt Motion on Trapezius Muscle Electromyography Activity.

The intended scapular motion is a strategy to strengthen the lower trapezius (LT). However, few studies have explored the effects of the intended scapular posterior tilt motion on selective LT activation. Thus, the present study investigated the effect of the intended scapular posterior tilt on the electromyography (EMG) activity of trapezius muscles during prone shoulder horizontal abduction (PSHA). Eighteen asymptomatic men performed three types of PSHA: (1) preferred PSHA, (2) PSHA with the intended scapular posterior tilt, and (3) PSHA with the intended scapular posterior tilt and trunk extension. EMG activity of the upper trapezius (UT), middle trapezius (MT), and LT were measured during PSHAs. Scapular posterior tilt angle, with and without the intended scapular posterior tilt, were measured using inclinometer. The results indicated that LT muscle activity increased when scapular posterior tilt was applied with and without trunk extension (14–16%), compared to the preferred condition, during PSHA (p < 0.05). However, the addition of trunk extension to PSHA with the intended scapular posterior tilt increased the UT muscle activity (28%) and the UT/LT (29%) and UT/MT (31%) ratios (p < 0.05). The scapular posterior tilt angle was higher (15%) when applying the intended scapular posterior tilt (p = 0.020). These findings suggest that the intended scapular posterior tilt may be a useful strategy for selective LT muscle activation.

Electromyographic Analysis of a Selective Exercise for the Serratus Anterior Muscle Among Patients With Frozen Shoulder and Subacromial Impingement Syndrome.

Patients with shoulder disorders show altered periscapular muscle activity (e.g., decreased serratus anterior and increased upper trapezius activities). We herein devised a novel method for strengthening serratus anterior without excessive upper trapezius activation, named squeezing ball exercise in which patients squeezed a ball between both elbows with maximum voluntary isometric contraction in the horizontal adduction direction with the arms elevated at a 45-degree angle. The present study aimed to investigate whether the squeezing ball exercise could produce high muscle activity in the serratus anterior in patients with frozen shoulder and subacromial impingement syndrome before the rehabilitation intervention. This is a proof-of-concept study. Serratus anterior and upper trapezius activities during squeezing ball exercise were evaluated using electromyography in 16 patients with frozen shoulders and subacromial impingement syndrome. Electromyography signals were normalized using maximal voluntary isometric contraction, and the muscle balance ratios (upper trapezius/serratus anterior) were calculated. The average serratus anterior and upper trapezius activity was 69.9% ± 30.8% and 10.2% ± 6.3% maximal voluntary isometric contraction during the squeezing ball exercise, respectively, whereas the upper trapezius-serratus anterior ratio of the affected side was 0.15 ± 0.07. The high serratus anterior activation and low upper trapezius-serratus anterior ratio during squeezing ball exercise could be attributed to the limb position where shortened serratus anterior exerts itself without painful subacromial impingement. Squeezing ball exercise could be a novel rehabilitation tool for patients with frozen shoulders and subacromial impingement syndrome.

Difference in Muscle Activity of Respiratory Muscle During Maximum Inspiration and Expiration Due to Position Change and Tool Use

Purpose : In this study, we aimed to measure how respiratory muscle activity changes as posture changes. We also aimed to measure the inspiratory sternocleidomastoid (SCM) and upper trapezius (UT) muscle activities as well as expiratory rectus abdominis (RA) and oblique abdominis (OA) muscle activities in healthy male and female university students in their twenties. Methods : Using the percentage of reference voluntary contraction (% RVC) with electromyography, we measured the SCM, UT, RA, and OA muscle activities in 16 healthy male and female university students in their 20s according to position change and breather tool use. Results : We found that the average value of inspiratory and expiratory muscle activities by posture was highest when using the breather tool. When using the tool with 10-mm and 2-mm straws for standard breathing at rest in the sitting position, a statistically significant increase in SCM, UT, and OA activities occurred (p < 0.05). For standard breathing at rest in the supine position, a statistically significant increase in SCM, RA, and OA activities occurred (p < 0.05). Conclusion : In clinical application, it may be better to use a respiratory muscle-strengthening tool to increase the activity of inspiratory and expiratory muscles.

Effects of the Additional Scapular Posterior Tilt Movement on Selective Muscle Activation of the Lower Trapezius during Prone Shoulder Extension

Effects of the Additional Scapular Posterior Tilt Movement on Selective Muscle Activation of the Lower Trapezius during Prone Shoulder Extension

Effect of arm position on spatial distribution of upper trapezius muscle activity during simulated car driving

The present study aimed to investigate the upper trapezius muscle activity during simulated car driving while adopting three different arm positions. Ten participants were instructed to maintain the following positions: hands on the steering wheel (Hands-On), hands not on the steering wheel (Hands-Off) and hands not on the steering wheel but arms on armrests (Armrests). During the tasks, multi-channel surface electromyography (EMG) was recorded from the upper trapezius muscle with 64 two-dimensionally distributed electrodes. Amplitudes of surface EMG in Armrests were lower than in Hands-On (p = 0.004). The spatial distribution of surface EMG changed with time in Hands-Off and Armrests (p < 0.05), but not in Hands-On (p > 0.05). These findings suggest that being freed from steering leads to the recruitment of various muscle fibers/motor units within the upper trapezius muscle and the use of armrests may help reduce the physiological burden loaded on the muscle of drivers.

Muscle activation of the upper trapezius and functional typing performance during computer typing task: A comparison of two different wrist immobilization methods

BackgroundThe 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. MethodsThe 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. ResultsThe 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). ConclusionThere 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.

Changes in muscle activation, oxygenation, and morphology following a fatiguing repetitive forward reaching task in young adult males and females

We sought to evaluate sex-specific 1) muscle activation patterns, hemodynamics, and swelling responses to short-cycle repetitive fatigue; 2) relationships between muscular responses and perceived fatigability. Asymptomatic participants (N = 26, 13 females) completed a repetitive pointing task until 8/10 on the Borg CR10 scale. Upper trapezius (UT), supraspinatus (SUPRA), and biceps brachii (BIC) muscle activation, activation variability (CV), median power frequency (MdPF) and thickness, and UT oxygenation were recorded. Males had higher BIC CV, UT and SUPRA MdPF, and UT and BIC thickness. Longer time to fatigue-terminal was correlated to greater SUPRA activation increase (ρ = 0.624) and BIC MdPF decrease (ρ = -0.674) in males, while in females it was correlated to greater (ρ = -0.657) and lower (ρ = 0.683) decrease of SUPRA and BIC CV, respectively. Male’s greater increase in SUPRA thickness correlated to greater increase in UT thickness and tissue oxygenation index, and to lower increase of UT deoxyhemoglobin. Females’ greater decrease of SUPRA MdPF correlated to greater decrease of UT MdPF, while greater UT activation increase was related to lower UT thickness increase. Results suggest that despite comparable time to fatigue-terminal, males have greater force-generating capacity and neuromuscular reliance on recruitment and excitation rates, while females have greater reliance on activation variability. Further, there are relationships between hemodynamic and swelling patterns in males, while there are relationships between activation and swelling patterns in females. Although there were no differences in experimental task-induced changes, there are sex-specific relationships between muscular patterns and perceived fatigability, which may help explain sex-specific mechanisms of musculoskeletal disorders.

An investigation of an ergonomics intervention to affect neck biomechanics and pain associated with smartphone use

Neck discomfort and pronounced neck flexion have been associated with smartphone use. Eye glasses with a 90 deg prism in each lens were investigated as a potential intervention to reduce awkward head and neck postures during activities involving viewing the device. Sixteen smartphone users with neck pain and 9 asymptomatic users performed a texting task on a smartphone with and without the prism glasses, in sitting and standing postures in a laboratory setting. Cervical erector spinae and upper trapezius muscle activity, head posture and motion, performance, discomfort and other subjective perceptions were assessed. Prism glasses reduced neck extensor muscle activity, neck flexion, and head tilt compared to the direct view. In the symptomatic group, the intervention produced less neck and shoulder discomfort compared to the direct view. This intervention could offer an alternative way of interacting with a smartphone while texting in stationary postures, by reducing exposure to pronounced flexed neck and head posture commonly seen in users, and thereby could reduce neck discomfort associated with smartphone use.

The Effect of Shoulder Abduction Angle on Trapezius Muscle Activity During Scapular Retraction Exercise.

Scapular retraction exercises are often prescribed to enhance scapular stabilization. To investigate the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT) activities, and UT/MT and UT/LT ratios during scapular retraction exercise with elastic resistance at different shoulder abduction angles. Descriptive laboratory study. Biomechanical analysis laboratory. Thirty-five asymptomatic individuals. Surface electromyography was used to evaluate UT, MT, and LT activities during the scapular retraction exercise at 0º, 45º, 90º, and 120º shoulder abductions. The mean muscle activity ranged from 15.8%-54.7% maximum voluntary isometric contraction (MVIC) for UT, 30.5%-51.6% MVIC for MT, 21.4%-25.5% MVIC for LT. A significant "muscle×angle" interaction was found (p<0.001). Post hoc analysis revealed that the MT was significantly more activated than UT and LT during both retraction at 0º (p<0.001; p=0.01, respectively) and 120º (p=0.03; p=0.002, respectively). During retraction at 45º and 90º, the LT generated significantly lower activity than the UT (p=0.02; p=0.03, respectively) and MT (p<0.001; p=0.002, respectively). Besides, UT/MT and UT/LT ratios during retraction at 0º were significantly lower than 45º (p=0.03; p=0.001, respectively) and 90º (p<0.001; p<0.001, respectively). Retraction at 90º resulted significantly higher UT/LT ratio than 45º (p=0.004) and 120º (p=0.004). Due to lower UT activity relative to MT, retraction at 0º, 45º, and 120º can be preferred in early shoulder training or rehabilitation. Additionally, retraction at 90º was the most effective exercise in activating entire trapezius muscle parts.

Adjustment effect during shoulder abduction training with the Hybrid Assistive Limb in a patient with postoperative C5 palsy

Standard shoulder rehabilitation procedures for patients with postoperative C5 palsy have not yet been established. We applied a wearable robot suit hybrid assistive limb (HAL) for a patient with postoperative C5 palsy and conducted shoulder abduction training with HAL. A 65-year-old woman was diagnosed with postoperative C5 palsy after undergoing cervical spine surgery. Five days after surgery, shoulder abduction training with HAL was initiated. The shoulder abduction angle and power and trapezius and deltoid activities were evaluated. Ten rehabilitation sessions were conducted until 82 days after surgery. Shoulder abduction training was safely and effectively performed from the first session. Her shoulder abduction angle and power improved at every session, and she could fully elevate her arm without any compensatory motion after the 10th session. Shoulder HAL training suppressed the muscular activity of the trapezius and activated that of the deltoid, especially in the earlier stages of rehabilitation. Moreover, it had an adjustment effect for obtaining normal shoulder motion, which might have promoted smoother arm elevation using errorless motor learning. These findings suggest that HAL is a useful tool for shoulder rehabilitation in patients with postoperative C5 palsy.

Ergonomic workstation reduces electrical activity of upper trapezius muscles, erector spinae muscles, and musculoskeletal complaints in agel fiber twisting process

Background: Humans' role in small industries as a source of labor is still dominant, mostly manual work. The research was conducted on manual workers in small agel fiber industries in Yogyakarta. Manual work is related to human strength and endurance. Ergonomic problems often arise in manual labor, including neck pain, back pain, and leg pain called musculoskeletal disorders. Non-ergonomic working conditions also increase the electrical activity of muscles. This study aims to reduce electrical muscle activity and musculoskeletal complaints by repairing an ergonomic workstation in the agel fiber twisting process.Methods: This research is an experimental study with 15 female subjects. The electrical activity of muscles is measured when working under conventional conditions (Period 1) and repairing an ergonomic work station (Period 2). The electrical activity of the muscles was measured using surface electromyography. Musculoskeletal complaints were measured before and after intervention with conventional conditions (Period 1) and ergonomic work station repair (Period 2). Musculoskeletal complaints were measured using the Nordic Body Map Questionnaire. The measurement data between the two periods were analyzed by using the paired samples t-test and the Wilcoxon signed-rank test.Results: The results showed a decrease in the upper trapezius muscles' electrical activity by 35.46% and the erector spinae muscles' electrical activity by 22.43%. The average of musculoskeletal complaints decreased by 23.77%, measured after working in period 1 and period 2.Conclusion: Ergonomic work station can reduce the electrical activity of the upper trapezius muscles, electrical activity of the erector spinae muscles, and musculoskeletal complaints in workers twisting the agel fiber rope.

Effect of conscious abdominal contraction on the activation of periscapular muscles in individuals with subacromial pain syndrome

BackgroundSynergism between shoulder and trunk muscles seems to be effective to increase periscapular muscle activation in asymptomatic subjects. The influence of conscious contraction of the abdominal muscles has not yet been studied in non-athlete subjects with pain. The study aimed to investigate the effect of the instruction for conscious activation of the abdominal muscles on the activity of the scapulothoracic muscles during shoulder exercises in subjects with subacromial pain syndrome. MethodThirty subjects with unilateral pain (mean age 52 ± 11 years) participated in this study. Three isometric and five dynamic exercises for the scapulothoracic muscles were assessed. The group without instruction just repeated the exercises, while the instruction group was evaluated before and after conscious abdominal training. The linear mixed model analysis was used to compare the muscle activation between groups. FindingsDifferences between groups after the conscious abdominal contraction for activation of middle and lower trapezius on the symptomatic side in the “Full can”(p = 0.03; effect size:0.92 middle trapezius); (p = 0.02; effect size:0.96 lower trapezius) and “Knee Push” (p = 0.01; effect size:0.75 lower trapezius). For asymptomatic side, the exercises “External Rotation Kneeling” (p = 0.04; effect size: 0.81 lower trapezius); (p = 0.00; effect size: 2.09 serratus anterior), “Knee Push” (p = 0.04; effect size:1.24 serratus anterior) and “Wall Slide” (p = 0.01; effect size: 1.03 serratus anterior). InterpretationConscious contraction of the abdominal muscle immediately alter the activation of the serratus anterior muscle during closed kinetic chain exercises on the asymptomatic side and increased activation of trapezius on the symptomatic side during shoulder open kinetic chain exercise.

Linking head and neck posture with muscular activity and perceived discomfort during prolonged smartphone texting

Prolonged use of the smartphone for texting was studied on a sample of 17 healthy young adult participants (11 females), who were asked to type interactively on a handheld device while standing and sitting. Upper body kinematics ad upper trapezius surface EMG were recorded to capture parameters of joint kinematics and muscular activity, which were then compared with self-reported indicators of discomfort through the Borg's CR 10 scale questionnaire. The results indicated that, while showing a similar postural strategy in both conditions that is assumed to be controlled by the visual system to maintain a constant viewing distance from the device, the participants adopted a “stiffer” posture of the head and neck during standing than when sitting, with a direct correlation between upper trapezius muscle activity, neck angle and perceived discomfort. The evidence obtained in this study highlights the importance of monitoring muscle activity and head and neck kinematics, to assess the biomechanical risk factors of neuromuscular disorders associated with smartphone overuse.

EMG activity of the serratus anterior and trapezius muscles during elevation and PUSH UP exercises

BackgroundElevation and push up (Pu) exercises are considered to be beneficial for the rehabilitation of shoulder complex pathology. Despite their clinical utility, there is a lack of evidence comparing scapulothoracic muscles recruitment during these exercises. ObjectiveTo evaluate the EMG activity of upper trapezius (UT), Lower Trapezius (LT), Upper Serratus anterior (USa) and Lower Serratus anterior (LSa) muscles during a variety of elevation and Pu exercises. MethodsThirteen healthy participants (non, athlete, male, mean ± standard deviation; age: 21.1 ± 1.8 years; height: 1.80 m ± 0.04; weight: 79 ± 12 kg) were assessed. EMG data was collected during Scaption, wall slide and elevation with external rotation (EleEr) with and without load. Pu classic, Pu plus (PuP) on stable/unstable surfaces and Pu with shoulder internal rotation were also assessed. ResultsUT had a significant higher activity during ‘Scaption load’ (p < .05) and LT in ‘EleEr load’ and ‘Scaption load’ (p < .05). USa and LSa had a significant higher activity on ‘PuP unstable surface’ and ‘PuP internal rotation’ compared to elevation exercises (p < .05). Scaption had greater activity ratio compared to the other exercises on UT/LT (p < .05). Pu variations had lower results in UT/USa and UT/LSa ratios compared to shoulder elevation exercises (p < .05). ConclusionsElevation exercises produce significant effects on upper and lower trapezius activation while Pu exercises on Sa muscles. Wall slide exercise notes the lowest activation in all muscles. A descending order of muscle activity during different variations of elevation and Pu exercises is provided in order to guide exercise selection in everyday clinical practice.