A new manual muscle test for assessing the entire trapezius muscle

Manual muscle testing (MMT), the trapezius muscle is an important part of the examination in patients with upper extremity dysfunction or pain. Purpose: The purpose of this study was to assess the reliability and validity of a new MMT that assesses the entire trapezius muscle instead of the usual method of separating it into three different parts. The new trapezius MMT is similar to the serratus anterior muscle test; however, the testing is performed in the frontal versus sagittal plane. Methods: A convenience sample of 11 subjects was recruited with no known shoulder pathology. Surface electromyography electrodes were placed on the upper, middle, and lower trapezius fibers according to a previously validated method and MMTs for the three different trapezius muscle test positions were normalized against the new trapezius test position. Results: The new trapezius MMT showed very high maximal voluntary isometric contraction (MVIC; 160.80%) for the upper trapezius muscle, high for the middle trapezius muscle (59.23%), and high for the lower trapezius muscle (47.54%) when normalized against the MVICs for each individual trapezius muscle tests. Conclusions: A new MMT that assesses the whole trapezius in its role as an upward scapular rotator was found to be reliable and valid.     

Surface EMG during the Push-up plus Exercise on a Stable Support or Swiss Ball: Scapular Stabilizer Muscle Exercise

[Purpose] Scapular stabilizer strengthening exercise is crucial for shoulder rehabilitation. The purpose of this study was to compare two types of push-up plus exercises, on a stable and unstable bases of support, using surface electromyography (EMG), to suggest an effective shoulder rehabilitation program. [Subjects and Methods] Ten healthy men volunteered for this study. All volunteers performed two sets of push-up plus exercise (standard push up and knee push up) on stable and unstable bases of support. The muscle activities of five important scapular stabilizer muscles (upper trapezius, middle trapezius, lower trapezius, serratus anterior, latissimus dorsi) were recorded during the exercise. [Results] The upper trapezius showed greater mean electric activation amplitude in the scapular retraction posture than in the scapular protraction posture, and the serratus anterior showed greater mean electric activation amplitude in the scapular protraction posture than in the scapular retraction posture. The root-mean-square normalized EMG values of the muscles were greater during the exercise performed on the unstable support than those on the stable support. [Conclusion] The standard push-up plus exercise on an unstable base of support helps to increase muscle activity, especially those of the upper/middle trapezius and serratus anterior.Key words: Scapular stabilizer, Push-up plus, Surface EMG     

Changes in electromyographic activity of deltoid muscles in women with shoulder pain during a functional task

BackgroundShoulder pain is one of the most common complaints of patients with musculoskeletal disorders in the shoulder and is usually caused by the Subacromial Impact Syndrome. Muscle imbalances can contribute to this syndrome leading to disorders that cause changes in muscle activity. The aim of this study was to determine whether pain causes changes in the electromyographic activity of the shoulder girdle muscles during an isometric task of arm elevation in the scapular plane.MethodThis is a comparative observational study using a simple convenience sampling method, composed of 22 women aged (44 ± 10) who were divided into two groups: 11 women with shoulder pain and 11 women without shoulder pain. The muscle activity evaluation was performed using surface electromyography of the muscles: anterior deltoid, middle deltoid, upper trapezius and middle trapezius, during an isometric task of arm elevation in the scapular plane. Independent Samples t-Test was used to analyze and compare the normalized electromyography data.ResultsResults revealed a significant increase in the activity of the anterior and middle deltoid muscles in women with shoulder pain compared to women without shoulder pain in the isometric task of arm elevation.ConclusionIt was concluded that the shoulder pain of the women evaluated caused changes in the activity of the anterior and middle deltoid muscles.     

Kinesiologic considerations for targeting activation of scapulothoracic muscles – part 2: trapezius

BackgroundThe trapezius is an extensive muscle subdivided into upper, middle, and lower parts. This muscle is a dominant stabilizer of the scapula, normally operating synergistically with other scapular muscles, most notably the serratus anterior. Altered activation, poor control, or reduced strength of the different parts of the trapezius have been linked with abnormal scapular movements, often associated with pain. Several exercises have been designed and studied that specifically target the different parts of the trapezius, with the goal of developing exercises that optimize scapular position and scapulohumeral rhythm that reduce pain and increase function.MethodsThis paper describes the anatomy, kinesiology, and pathokinesiology of the trapezius as well as exercises that selectively target the activation of the different parts of this complex muscle.ConclusionsThis review provides the anatomy and kinesiology of the trapezius muscle with the underlying intention of understanding how this muscle contributes to the normal mechanics of the scapula as well as the entire shoulder region. This paper can guide the clinician with planning exercises that specifically target the different parts of the trapezius. It is recommended that this paper be read as a companion to another paper: Kinesiologic considerations for targeting activation of scapulothoracic muscles – part 1: serratus anterior.     

The Effect of Shoulder Mobilization on Scapular and Shoulder Muscle Activity During Resisted Shoulder Abduction: A Crossover Study of Asymptomatic Individuals

ObjectiveThe primary aim was to investigate the effect of inferior shoulder mobilization on scapular and shoulder muscle activity during resisted shoulder abduction in asymptomatic individuals.MethodsThis was a lab-based, repeated-measures, crossover, randomized controlled study. Twenty-two participants were recruited. The order of experimental conditions was randomized. Each participant performed 5 repetitions of resisted shoulder abduction before and after the control and mobilization (grade +IV inferior shoulder mobilization, 3 sets, 60 seconds) conditions. Surface electromyography recorded the muscle activity of anterior, middle, and posterior deltoid; supraspinatus; infraspinatus; upper and lower trapezius; serratus anterior; and latissimus dorsi muscles.ResultsMuscle activity levels reduced for infraspinatus (11.3% MVIC, 95% CI: 1.7-20.8), middle (22.4% MVIC, 95% CI: 15.9-28.8) and posterior deltoid (8.7 % MVIC, 95% CI: 4.6-12.9), and serratus anterior (-28.1% MVIC, 95% CI: 15.6-40.8) muscles after the mobilization condition during the eccentric phase of shoulder abduction. No carryover effects were observed, and within-session reliability was excellent (intraclass correlation coefficient scores ranging from 0.94 to 0.99).ConclusionOur findings suggest that inferior glenohumeral mobilization reduces activity levels of some scapular and shoulder muscles. Given the exploratory nature of our study, changes in muscle activity levels may have been found by chance. Confirmatory studies are required.     

Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement

BACKGROUND AND PURPOSE: Treatment of patients with impingement symptoms commonly includes exercises intended to restore "normal" movement patterns. Evidence that indicates the existence of abnormal patterns in people with shoulder pain is limited. The purpose of this investigation was to analyze glenohumeral and scapulothoracic kinematics and associated scapulothoracic muscle activity in a group of subjects with symptoms of shoulder impingement relative to a group of subjects without symptoms of shoulder impingement matched for occupational exposure to overhead work. SUBJECTS: Fifty-two subjects were recruited from a population of construction workers with routine exposure to overhead work. METHODS: Surface electromyographic data were collected from the upper and lower parts of the trapezius muscle and from the serratus anterior muscle. Electromagnetic sensors simultaneously tracked 3-dimensional motion of the trunk, scapula, and humerus during humeral elevation in the scapular plane in 3 handheld load conditions: (1) no load, (2) 2. 3-kg load, and (3) 4.6-kg load. An analysis of variance model was used to test for group and load effects for 3 phases of motion (31(-60(, 61(-90(, and 91(-120(). RESULTS: Relative to the group without impingement, the group with impingement showed decreased scapular upward rotation at the end of the first of the 3 phases of interest, increased anterior tipping at the end of the third phase of interest, and increased scapular medial rotation under the load conditions. At the same time, upper and lower trapezius muscle electromyographic activity increased in the group with impingement as compared with the group without impingement in the final 2 phases, although the upper trapezius muscle changes were apparent only during the 4.6-kg load condition. The serratus anterior muscle demonstrated decreased activity in the group with impingement across all loads and phases. CONCLUSION AND DISCUSSION: Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work. [Ludewig PM, Cook TM. Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement.     

The effects of shoulder joint abduction angles on the muscle activity of the serratus anterior muscle and the upper trapezius muscle while vibrations are applied

[Purpose] The purpose of this study was to examine the ratio between the upper trapezius and the serratus anterior muscles during diverse shoulder abduction exercises applied with vibrations in order to determine the appropriate exercise methods for recovery of scapular muscle balance. [Subjects and Methods] Twenty-four subjects voluntarily participated in this study. The subjects performed shoulder abduction at various shoulder joint abduction angles (90°, 120°, 150°, 180°) with oscillation movements. [Results] At 120°, all the subjects showed significant increases in the muscle activity of the serratus anterior muscle in comparison with the upper trapezius muscle. However, no significant difference was found at angles other than 120°. [Conclusion] To selectively strengthen the serratus anterior, applying vibration stimuli at the 120° shoulder abduction position is considered to be appropriate.Key words: Serratus anterior, Upper trapezius, Vibration     

Three-dimensional scapulothoracic motion during active and passive arm elevation

BACKGROUND: Scapulothoracic muscle activity is believed to be important for normal scapulothoracic motion. In particular, the trapezius and serratus anterior muscles are believed to play an important role in the production and control of scapulothoracic motion. The aim of this study was to determine the effects of different levels of muscle activity (active versus passive arm elevation) on three-dimensional scapulothoracic motion. METHODS: Twenty subjects without a history of shoulder pathology participated in this study. Three-dimensional scapulothoracic motion was determined from electromagnetic sensors attached to the scapula, thorax and humerus during active and passive arm elevation. Muscle activity was recorded from surface electrodes over the upper and lower trapezius, serratus anterior, anterior and posterior deltoid, and infraspinatus muscles. Differences in scapulothoracic motion were calculated between active and passive arm elevation conditions. FINDINGS: Scapular motion was observed during the trials of passive arm elevation; however, there was more upward rotation of the scapula, external rotation of the scapula, clavicular retraction, and clavicular elevation under the condition of active arm elevation. This was most pronounced for scapular upward rotation through the mid-range (90-120 degrees) of arm elevation. INTERPRETATION: The upper and lower trapezius and serratus anterior muscles have an important role in producing upward rotation of the scapula especially throughout the mid-range of arm elevation. Additionally, it appears that capsuloligamentous and passive muscle tension contribute to scapulothoracic motion during arm elevation. Assessment of the upper and lower trapezius and serratus anterior muscles and upward rotation of the scapula should be part of any shoulder examination.     

Modifying a shrug exercise can facilitate the upward rotator muscles of the scapula

Background

Scapular dyskinesis, characterised by drooping scapulae and reduced upward rotation, has been implicated in the presentation of a number of shoulder disorders. Traditionally, in shoulder rehabilitation programmes, the shrug exercise has been prescribed to facilitate upward rotation of the scapula by strengthening the upper trapezius muscle. The aim of this research was to compare muscle activation levels during the standard shrug and the upward rotation shrug in a normal and pathological population.

Methods

Surface electrodes recorded electromyographical activity from upper trapezius, middle trapezius, lower trapezius and serratus anterior muscles in 23 normal participants and 14 participants with multi-directional shoulder instability. Participants completed 10 trials of the standard shrug exercise at 0° of shoulder abduction and the upward rotation shrug exercise at 30° of shoulder abduction in the coronal plane. Muscle activity was expressed as a percentage of maximum voluntary isometric contraction.

Findings

The four muscles tested performed at a higher intensity during the modified shrug than the standard shrug. Upper trapezius and lower trapezius activity was significantly greater (P < 0.05) in both populations. Though for middle trapezius and serratus anterior muscles, the modified shrug was statistically significant only in the normal population, P = 0.031 and P = < 0.001 respectively.

Interpretation

The upward rotation shrug is a more effective exercise for eliciting muscle activity of the upper and lower trapezius than the standard shrug in a normal and multi-directional instability population. Clinically, the upward rotation shrug might be useful to address scapular dyskinesis involving drooping shoulders and reduced scapula upward rotation.     

Effect of a Multi-Air-Cushion Biofeedback Device (MABD) on Shoulder Muscles during the Dynamic Hug Exercise

[Purpose] We developed a multi-air-cushion biofeedback device (MABD) to assist the dynamic hug exercise, and investigated the effects of MABD on the shoulder muscles during the dynamic hug exercise. [Subjects] Twelve males aged 22–32 years were recruited. [Methods] We measured the right side serratus anterior, lower trapezius, and upper trapezius muscle activities during the dynamic hug exercise with and without MABD. [Results] The serratus anterior and lower trapezius muscles activities significantly increased during the dynamic hug exercise with MABD compared to without it. The upper trapezius muscle significantly decreased during the dynamic hug exercise with MABD compared to without it. [Conclusion] The results suggest that the dynamic hug exercise with MABD is an effective scapular stability exercise.Key words: Biofeedback, Dynamic hug exercise, Scapular stability     

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.     

The Effects of Vibration Stimuli Applied to the Shoulder Joint on the Activity of the Muscles Around the Shoulder Joint

[Purpose] The present study compared the muscle activity of the upper trapezius with those of the serratus anterior and the lower trapezius when slings, unstable surfaces, were laterally vibrated, to examine the effects of vibration during sling exercises on shoulder stabilization muscles. [Methods] The subjects performed push-up exercises on a sling and maintained isometric contraction in the final stage, while vibration was manually administered to the rope of the sling during the isometric-contraction stage. Vibration within a range of 10 cm was delivered for five seconds at a frequency of 1 Hz in time with a metronome. Vibrations were applied for five seconds at 3 Hz and 3.5 Hz, respectively. [Results] The serratus anterior showed a significant differences between isometric contraction with vibration of 3 Hz and isometric contraction with vibration of 3.5 Hz. [Conclusion] The upper trapezius and the lower trapezius showed prominent changes in muscle activity at 3.5 Hz, and the serratus anterior showed prominent changes in muscle activity at 3 Hz and 3.5 Hz. Therefore, as vibration frequency increased, making the load-bearing surface more unstable, the recruitment of the upper trapezius, the lower trapezius, and the serratus anterior increased. To perform exercises that selectively strengthen the serratus anterior, the exercises should be performed at a vibration frequency of 3 Hz.Key words: Vibration, Shoulder joint, Muscle activity     

Electromyographic response of shoulder muscles to acute experimental subacromial pain

This study investigated effects of experimentally-induced subacromial pain, induced via hypertonic saline injection, on shoulder muscles activity. Electromyographic activity of 20 healthy participants was assessed for humeral elevation and descent for the control and experimental pain conditions, using fine wire electrodes for subscapularis and supraspinatus and surface electrodes for middle deltoid, upper trapezius, lower trapezius, infraspinatus, and serratus anterior. Normalized mean amplitudes were analyzed for each muscle for four phases for elevation and descent, respectively. Repeated measures analysis of variances (ANOVAs) were used to determine differences between muscle activity in the control and experimental condition for the four phases of elevation and descent. Differences for mean normalized amplitudes were not significant during humeral elevation. Increased activity was found for the pain condition for serratus anterior and middle deltoid during the first (120–90°) and third (60–30°) parts and decreased activity for infraspinatus in the second half of descent (60–0°). No significant differences were found during descent for upper and lower trapezius, subscapularis and supraspinatus. While increased serratus anterior activity during 60–30° of descent may be protective, increased middle deltoid and decreased infraspinatus activity during the same range may threaten subacromial tissues in that range. Overall the changes in muscle activation were individual specific, particularly during the concentric elevation phase.     

A COMPARISON OF CHANGE IN 3D SCAPULAR KINEMATICS WITH MAXIMAL CONTRACTIONS AND FORCE PRODUCTION WITH SCAPULAR MUSCLE TESTS BETWEEN ASYMPTOMATIC OVERHEAD ATHLETES WITH AND WITHOUT SCAPULAR DYSKINESIS

Background

The significance of scapular dyskinesis is being challenged due to a lack of the association with pain and ability to predict injury in athletic populations. However, it is unknown whether asymptomatic overhead athletes with dyskinesis cope by normalizing scapular position with higher demand activities.

Hypothesis/Purpose

The purpose of this study was to compare change in scapular kinematics from an active unweighted contraction to a maximal isometric contraction in asymptomatic overhead athletes with and without scapular dyskinesis. Secondarily, force generated with manual muscle tests were explored for differences and relationships with kinematics.

Study Design

Cross‐sectional laboratory study

Methods

Twenty‐five matched asymptomatic overhead athletes with (n=14) and without (n=11) scapular dyskinesis, defined with a reliable and validated clinical method, participated in this study. Three‐dimensional scapular kinematics were evaluated in an active unweighted condition, and during maximal isometric contractions at 90 ° of shoulder flexion. Isometric force produced with lower trapezius and serratus anterior manual muscle tests were assessed with a dynamometer. Changes in scapular kinematics were compared between groups. Differences in force generated with manual muscle tests between groups and relationships with kinematics were explored.

Results

Athletes with dyskinesis demonstrated greater deficits in scapular upward rotation with maximal contraction (p=<0.001), less external rotation (p=0.036) and weaker lower trapezius manual muscle test strength (p=0.031). Lower trapezius (p=0.003;r=0.57) and serratus anterior (p=0.042;r=0.41) manual muscle test strength deficits were fair to moderately associated with a lack of scapular upward rotation during maximal contraction.

Conclusion

Small to moderate changes in scapular kinematics are normal responses to a maximal contraction, but with scapular dyskinesis this response is accentuated. Athletes with dyskinesis generate less force with lower trapezius manual muscle testing compared to athletes without dyskinesis. Decreased strength with lower trapezius and serratus anterior manual muscle testing was also related to a lack of upward rotation in all athletes.

Level of Evidence

3     

Muscle activation patterns in the scapular positioning muscles during loaded scapular plane elevation: The effects of Latent Myofascial Trigger Points

BackgroundLatent Myofascial Trigger Points are pain-free neuromuscular lesions that have been found to affect muscle activation patterns in the unloaded state. The aim was to extend these observations to loaded motion by investigating muscle activation patterns in upward scapular rotator muscles (upper and lower trapezius and serratus anterior) hosting Latent Myofascial Trigger Points simultaneously with lesion-free synergists for shoulder abduction (infraspinatus and middle deltoid). This approach allowed examination of the effects of these lesions on both their hosts and their lesion-free synergists in order to understand their effects on the performance of shoulder abduction.MethodsSurface electromyography was employed to measure the timing of onset of muscle activation of the upper and lower trapezius and serratus anterior (upward scapular rotators), infraspinatus (rotator cuff) and middle deltoid (abductor of the arm) initially without load and then with light (1–4 kg) dumbbells. Comparisons were made between control (no Latent Trigger Points; n = 14) and Latent Trigger Point (n = 28) groups.FindingsThe control group displayed a relatively stable sequence of muscle activation that was significantly different in timing and variability to that of the Latent Trigger Point group in all muscles except middle deltoid (all P < 0.05). The Latent Trigger Point group muscle activation pattern under load was inconsistent, with the only common feature being the early activation of the infraspinatus.InterpretationThe presence of Latent Trigger Points in upward scapular rotators alters the muscle activation pattern during scapular plane elevation, potentially predisposing to overuse conditions including impingement syndrome, rotator cuff pathology and myofascial pain.     

Electromyographic study of the scapular rotators during arm abduction in the scapular plane

In 20 healthy, young adult male subjects, the muscular activity of the upper, middle and lower trapezius and the lower digitations of the serratus anterior were studied electromyographically during arm abduction in the plane of the scapula. The patterns of electrical activity of the trapezius and lower serratus anterior muscles were observed to increase progressively during abduction of the arm; however, a plateau phase was demonstrated in all four of the muscle parts studied. Despite the presence of considerable individual variability, common trends were observed in muscular activity patterns. It is believed that the patterns of muscle activity may be closely related to mechanical factors such as scapulohumeral rhythm and a migrating scapular Instantaneous Centre of Rotation (ICR) during arm elevation.     

Changes in upper-extremity muscle activities due to head position in subjects with a forward head posture and rounded shoulders

[Purpose] This study investigated upper-extremity muscle activities in natural, ideal, and corrected head positions. [Subjects and Methods] Forty subjects with a forward head posture and rounded shoulder were recruited and randomly assigned to the natural head position group (n = 13), ideal head position group (n = 14), or corrected head position group (n = 13). Muscle activities were measured using a four-channel surface electromyography system at the sternocleidomastoideus, upper and lower trapezius, and serratus anterior muscles on the right side during an overhead reaching task. [Results] The muscle activities of the upper trapezius and serratus anterior differed significantly among head positions. Post hoc tests revealed significant differences between natural and ideal head positions, and natural and ideal head positions for both the upper trapezius and serratus anterior. [Conclusion] Recovery of normal upper trapezius and serratus anterior muscle functions plays an important role in correcting forward head posture and rounded shoulders.Key words: Forward head posture, Muscle activity, Round shoulder     

Comparison of scapular kinematics and muscle strength between those with a positive and a negative Scapular Assistance Test

BackgroundThe Scapular Assistance Test was suggested to directly assess the influence of scapular motion on pain and indirectly measure the function of the scapular rotators. However, it is still not clear if individuals with a positive Scapular Assistance Test actually present changes in scapular motion and muscle strength. This study compared scapular kinematics and muscle strength between those with a positive Scapular Assistance Test and those with a negative Scapular Assistance Test.MethodsFifty individuals with shoulder pain were randomly allocated to: positive (n = 25) or negative Scapular Assistance Test (n = 25) group. Scapular kinematics was measured during elevation and lowering of the arm. Strength of the serratus anterior and lower trapezius was also measured. Two-way analysis of variance was used to compare kinematics between groups. Unpaired Student's t-test and Mann-Whitney test were used to compare strength of serratus anterior and lower trapezius, respectively.FindingsThere were no differences (P > 0.05) in scapular internal rotation and upward rotation between both groups. For scapular tilt, there was group main effect (P < 0.05) during elevation and lowering of the arm, whereas the positive Scapular Assistance Test group presented greater scapular anterior tilt. There was no difference (P > 0.05) in strength between groups.InterpretationIndividuals with a positive Scapular Assistance Test are more likely to present decreased scapular posterior tilt in those with shoulder pain. Strength of the scapular muscles seems to be same in those with a positive and a negative Scapular Assistance Test.     

Scapular movement training versus standardized exercises for individuals with chronic shoulder pain: protocol for a randomized controlled trial

BackgroundScapular focused exercise interventions are frequently used to treat individuals with shoulder pain. However, evidence for changes in scapular motion after intervention is limited.ObjectiveTo compare the effects of scapular movement training versus standardized exercises for individuals with shoulder pain.MethodsThis will be a single-blinded randomized controlled trial. Sixty-four individuals with shoulder pain for at least 3 months, scapular dyskinesis, and a positive scapular assistance test will be randomly allocated to one of two groups: Scapular Movement Training (group 1) and Standardized Exercises (group 2). Group 1 will receive education about scapular position and movement, and be trained to modify the scapular movement pattern. Group 2 will perform stretching and strengthening exercises. Both groups will be treated twice a week for eight weeks. Three-dimensional scapular kinematics and muscle activity of the serratus anterior and upper, middle, and lower trapezius during elevation and lowering of the arm will be assessed at baseline and after 8 weeks of treatment. Pain intensity, function, fear avoidance beliefs, and kinesiophobia will be assessed at baseline and after 4 and 8 weeks of treatment, and 4 weeks after the end of treatment.ConclusionsThe results of this study may contribute to a better understanding of the efficacy of scapular focused treatments for individuals with shoulder pain. Clinical trial registration: NCT03528499     

Trapezius muscle activation levels and ratios during scapular retraction exercises: A comparative study between patients with subacromial impingement syndrome and healthy controls

BackgroundLittle is known about trapezius muscle activities during scapular retraction exercises in patients with subacromial impingement syndrome. The aim of this study was to compare upper trapezius, middle trapezius and lower trapezius muscle activity and upper/middle and upper/lower trapezius ratios between patients with subacromial impingement syndrome and healthy individuals during six scapular retraction exercises.MethodsTwenty-two patients with subacromial impingement syndrome and 22 healthy individuals participated. Upper, middle, and lower trapezius activities were measured by surface electromyography, while the participants performed six scapular retraction exercises at different shoulder abduction angles in a standing position. Upper/middle and upper/lower trapezius ratios were also calculated. Repeated-measures analyses of variance were performed to determine whether muscle activation levels and ratios differed between groups during exercises.FindingsThere was no significant exercise × group interactions for upper, middle, and lower trapezius activation levels and upper/middle and upper/lower trapezius ratios (P > .05). A main effect for the exercise was observed for the upper/middle and upper/lower trapezius ratios (P < .05).InterpretationCompared to healthy individuals, patients with subacromial impingement syndrome did not exhibit different upper, middle, and lower trapezius activity and had similar upper/middle and upper/lower trapezius ratios during the various scapular retraction exercises. Therefore, scapular retraction exercises with various shoulder abduction could be safely offered for the patients with subacromial impingement syndrome since it does not lead to abnormal compensatory trapezius muscle activity. If the goal is to minimize upper/middle and upper/lower trapezius ratios, the scapular retraction exercises at 0° shoulder abduction may be used in early stage of shoulder rehabilitation.