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.     

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.     

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.     

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.     

Long thoracic neuropathy from athletic activity.

Four cases of long thoracic mononeuropathy associated with sports participation are presented. Each patient developed shoulder pain or dysfunction after an acute event or vigorous activity, and demonstrated scapular winging consistent with serratus anterior weakness. The diagnosis was confirmed with electromyography in each case. It is suggested that the athletic activity caused a stretch injury to the long thoracic nerve. Conservative management, consisting of range of motion exercises for the shoulder and strengthening of the serratus anterior muscle, resulted in a favorable outcome in all patients.     

Influence of reducing anterior pelvic tilt on shoulder posture and the electromyographic activity of scapular upward rotators

BackgroundModifications of posture in a segment may influence the posture of adjacent and nonadjacent segments and muscular activity. The spine–shoulder and spine–pelvis relationships suggest that the pelvis may influence shoulder posture.ObjectiveTo investigate the effect of the active reduction of the anterior pelvic tilt on shoulder and trunk posture during static standing posture and on the electromyographic activity of the scapular upward rotators during elevation and lowering of the arm.MethodsThirty-one young adults were assessed in a relaxed standing position and a standing position with 30% active reduction of the anterior pelvic tilt. The pelvic tilt, trunk posture, and forward shoulder posture during the static standing posture and the electromyographic activity during elevation and lowering of the arm were assessed.ResultsPaired t-tests indicated that the active reduction of the anterior pelvic tilt reduced the trunk extension (MD = 1.09; 95%CI = −2.79 to −1.03). There were no effects on the forward shoulder posture (MD = 0.09; 95%CI = −0.92 to 1.09). Repeated measures of analyses of variance indicated an increase in lower trapezius electromyographic activity (MD = 3.6; 95%CI = 1.28 to 5.92). There was a greater reduction in upper trapezius activity after pelvic tilt reduction during arm elevation (MD = 1.52%; 95%CI = −2.79 to −0.25) compared to that during the lowering phase. There were no effects of pelvic tilt reduction on the electromyographic activity of the serratus anterior (MD = 3.26; 95%CI = −3.36 to 9.87).ConclusionThe influence of pelvic posture on the trunk posture and lower trapezius activation should be considered when assessing or planning exercise for individuals with shoulder or trunk conditions.     

Electromyographic activity of the serratus anterior and pectoralis major during isometric scapular protraction at different resistance intensities in subjects with and without a winged scapula

BackgroundDuring maximal isometric protraction, it is important to determine the optimal resistance intensity in subjects with a winged scapula, for inducing isolated activity of the serratus anterior against the pectoralis major, which is activated as a synergistic muscle. The aim of the present study was to determine electromyographic activities of the serratus anterior and pectoralis major muscles during isometric shoulder protraction at different levels in subjects with and without a winged scapula.MethodsThirty male subjects performed isometric shoulder protraction in a sitting position at different resistance intensity levels (100%, 80%, and 60% of maximal protraction strength). Surface electromyographic data of the serratus anterior and pectoralis major muscles were gathered simultaneously using fixed instrumentation to measure isometric shoulder protraction.FindingsMuscle activity of the serratus anterior in subjects without a winged scapula was significantly greater than that of subjects with a winged scapula across all three conditions, whereas muscle activity of the pectoralis major was lower in subjects without a winged scapula. In addition, winged scapula muscle activity corresponding to maximal protraction was significantly greater than that in the submaximal condition.InterpretationIn a clinical setting, submaximal resistance can be more optimal than maximal effort during isometric shoulder protraction in individuals with a winged scapula.     

Proximal myofascial pain in patients with distal complex regional pain syndrome of the upper limb

BackgroundPatients suffering from complex regional pain syndrome (CRPS) endure myofascial-related pain in at least 50% of cases.AimsTo evaluate the association of upper limb CRPS with myofascial pain in muscles that might influence arm or hand pain, and to evaluate whether the paraspinal skin and subcutaneous layers’ tenderness and allodynia are associated with CRPS.MethodsA case-control study comprising 20 patients presenting with upper limb CRPS, and 20 healthy controls matched for sex and age, were evaluated in the thoracic paraspinal area and myofascial trigger points (MTrPs) (infraspinatus, rhomboids, subclavius, serratus posterior superior and pectoralis minor) via a skin rolling test.ResultsThe prevalence of MTrPs in the affected extremity of the subjects was significantly higher than in the right limb of the controls: 45% exhibited active and latent MTrPs in the infraspinatus muscle (χ² = 11.613, p = 0.001); 60% in active and latent MTrPs in the subclavius muscle (χ² = 17.143, p < 0.001); and in the pectoralis minor muscle (χ2 = 13.786, p < 0.001). In addition, 55% of the cases exhibited active and latent MTrPs in the serratus posterior superior muscle (χ² = 15.172, p < 0.001). Significant differences between the groups in skin texture and pain levels (p = 0.01, p < 0.001, respectively) demonstrated that CRPS patients felt more pain, and their skin and subcutaneous layers were much tighter than in the healthy controls.ConclusionThere is a high prevalence of MTrPs in the shoulder and upper thoracic area muscles in subjects who suffer from CRPS. We recommend adding an MTrPs evaluation to the standardized examination of these patients.     

Comparison of core neuromuscular control and lower extremity postural stability in athletes with and without shoulder injuries

BackgroundThe kinetic chain theory is widely used as a rationale for the inclusion of core stability training in athletes. Core stability (muscle capacity and neuromuscular control) impairments may result in less than optimal performance and abnormal force dissipation to the shoulder complex that could lead to shoulder injuries. However, a paucity of literature exists to support this relationship, and no previous studies have investigated the relationship between isolated core neuromuscular control and shoulder injuries. Additionally, lower extremity postural stability has been associated with athletic function and may also be associated with shoulder injuries. The purpose of this study was to compare biomechanical measures of isolated core neuromuscular control and lower extremity postural stability between athletes with and without non-traumatic shoulder injuries.MethodsEighty athletes (55 males, age: 21.2 ± 3.3 years, 40 with a current shoulder injury) completed biomechanical measures of isolated core neuromuscular control and lower extremity postural stability. Athletes were matched by age, gender, body mass index, and sport type. MANOVAs were used to assess differences between measures of core neuromuscular control and lower extremity postural stability between groups.FindingsThere were no statistically significant differences between athletes with and without shoulder injuries for the static core neuromuscular control measures, F(4,75) = 0.45, P = 0.78, η² = 0.02; dynamic core neuromuscular control measures, F(4,75) = 0.81, P = 0.52, η² = 0.04; or lower extremity postural stability measures, F(8,61) = 0.85, P = 0.56, η² = 0.10.InterpretationAlthough core stability is widely incorporated in rehabilitation of athletes with shoulder injuries, athletes with current non-traumatic shoulder injuries may not present with impairments in core neuromuscular control or lower extremity postural stability.     

Use of unstable exercises in periscapular muscle activity: A systematic review and meta-analysis of electromyographic studies

BackgroundThe use of unstable surfaces has been proposed to increase the neuromuscular demand. This strategy has been adopted to generate an increase in the activity of periscapular muscles due to its role in the stabilization of the scapula. However, the influence of this instability on the EMG activity remains uncertain. The aim of this study was to analyze the effects of using unstable surfaces on the EMG activity of the periscapular muscles.MethodsA comprehensive search in the PubMed, EMBASE, SCIELO, Web of Science, SCOPUS, Cochrane and LILACS databases was undertaken from their year of inception up to December 2019. Studies which directly investigated the EMG activity of periscapular muscles in healthy individuals while performing exercises for the upper limbs in stable and unstable conditions.ResultsA total of 33 studies which evaluated a total of 678 healthy individuals were found according to the eligibility criteria. A meta-analysis identified that the EMG activity of the upper trapezius showed a trivial increase with the insertion of the unstable surface (P = 0.04; SMD = 0.14 [95%CI 0.00, 0.27]). No significant effects were observed on the middle trapezius (P = 0.10) and lower trapezius (P = 0.25). A decrease of the anterior serratus EMG activity with a small effect size was observed by implementing an unstable surface (P = 0.01; SMD = −0.21 [95%CI -0.36, −0.05]).ConclusionThe use of unstable surfaces generated a trivial increase in the upper trapezius activity, and a slight decrease in the anterior serratus activity. No effect was observed on the middle and lower trapezius.     

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.     

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     

Regional interdependence and manual therapy directed at the thoracic spine

Abstract

Thoracic spine manipulation is commonly used by physical therapists for the management of patients with upper quarter pain syndromes. The theoretical construct for using thoracic manipulation for upper quarter conditions is a mainstay of a regional interdependence (RI) approach. The RI concept is likely much more complex and is perhaps driven by a neurophysiological response including those related to peripheral, spinal cord and supraspinal mechanisms. Recent evidence suggests that thoracic spine manipulation results in neurophysiological changes, which may lead to improved pain and outcomes in individuals with musculoskeletal disorders. The intent of this narrative review is to describe the research supporting the RI concept and its application to the treatment of individuals with neck and/or shoulder pain. Treatment utilizing both thrust and non-thrust thoracic manipulation has been shown to result in improvements in pain, range of motion and disability in patients with upper quarter conditions. Research has yet to determine optimal dosage, techniques or patient populations to which the RI approach should be applied; however, emerging evidence supporting a neurophysiological effect for thoracic spine manipulation may negate the need to fully answer this question. Certainly, there is a need for further research examining both the clinical efficacy and effectiveness of manual therapy interventions utilized in the RI model as well as the neurophysiological effects resulting from this intervention.     

The influence of different sitting postures on head/neck posture and muscle activity

To date the influence that specific sitting posture has on the head/neck posture and cervico-thoracic muscle activity has been insufficiently investigated. Therefore the aim of this study was to investigate whether three different thoraco-lumbar sitting postures affect head/neck posture and cervico-thoracic muscle activity.Twenty (10 men, 10 women) asymptomatic subjects were placed in 3 standardized thoraco-lumbar sitting postures (lumbo-pelvic, thoracic upright and slump) to investigate their influence on cervico-thoracic muscle activity and head/neck posture.There were significant differences in lumbar and thoracic curvatures in the 3 different sitting postures (P < 0.002). Slump sitting was associated with greater head/neck flexion, anterior translation of the head (P < 0.001) and increased muscle activity of cervical erector spinae (CES) compared to thoracic and lumbo-pelvic sitting (P = 0.001). Thoracic upright sitting showed increased muscle activity of thoracic erector spinae (TES) compared to slump and lumbo-pelvic postures (P = 0.015). Upper trapezius (UT) demonstrated no significant difference in muscle activation in the 3 sitting postures (P < 0.991). This study demonstrates that different sitting postures affect head/neck posture and cervico-thoracic muscle activity. It highlights the potential importance of thoraco-lumbar spine postural adjustment when training head/neck posture.     

Identification of patient subgroups and risk factors for persistent arm/shoulder pain following breast cancer surgery

PurposeIn this prospective, longitudinal study, we extend our findings on persistent breast pain in patients (n = 398) following breast cancer surgery and evaluate the prevalence and characteristics of persistent pain in the arm/shoulder. In addition, differences in the severity of common symptoms and quality of life outcomes measured prior to surgery, among the arm pain classes, were evaluated.Methods and samplePatients were recruited from Breast Care Centers located in a Comprehensive Cancer Center, two public hospitals, and four community practices. Patients were assessed prior to and monthly for six months following breast cancer surgery.ResultsUsing growth mixture modeling, patients were classified into no (41.6%), mild (23.6%), and moderate (34.8%) arm pain classes based on ratings of worst arm/shoulder pain. Compared to the no pain class, patients in the moderate pain class were significantly younger, had a higher body mass index, and were more likely to report preoperative breast pain and swelling in the affected breast. In addition, patients in the moderate pain class reported higher levels of depression, anxiety, and sleep disturbance than the no pain class.ConclusionsFindings suggest that approximately 35% of women experience persistent levels of moderate arm/shoulder pain in the first six months following breast cancer surgery. Moderate arm/shoulder pain is associated with clinically meaningful decrements in functional status and quality of life.     

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     

Exploration of the clinical course of frozen shoulder: A longitudinal multicenter prospective study of functional impairments

BackgroundContradictory evidence exists regarding the clinical course of frozen shoulder (FS).ObjectivesTo explore the clinical course of FS regarding disabilities, pain, range of motion (ROM), muscle strength, scapular upward rotation, and proprioception and to establish longitudinal correlations between these variables.MethodsPatients with FS were prospectively followed for 9 months at 3-month intervals. Assessment included the Disabilities of the Arm, Shoulder and Hand questionnaire; visual analogue scale for pain; an inclinometer for shoulder external rotation (ER), internal rotation (IR), flexion, and abduction ROM, and scapular upward rotation and proprioception, as well as handheld dynamometry for muscle strength in shoulder abduction, ER, and IR.ResultsInitially, 149 patients (98 females; mean (SD) age 53 (9) years) were included, with 88 completing all follow-up assessments. Most variables showed early improvement in the clinical course of FS, particularly ER and IR at 90° abduction, which continued to improve from 6 to 9 months of follow-up. Associations were observed between disabilities and pain (r = 0.61), disabilities/pain and ROM (r=-0.62 to -0.59 and r=-0.47 to -0.39, respectively), disabilities/pain and muscle strength (r=-0.24 to -0.35 and r=-0.36 to -0.17, respectively), and between disabilities/pain and scapular upward rotation below shoulder level (r = 0.23 to 0.38 and r = 0.24 to 0.30, respectively). ROM correlated with muscle strength (r = 0.14 to 0.44), while both ROM and ER muscle strength correlated with scapular upward rotation below shoulder level (r=-0.37 to -0.23 and r=-0.17 to -0.12, respectively). Muscle strength correlated with scapular upward rotation above shoulder level (r = 0.28 to 0.38) and lift-off muscle strength correlated with joint repositioning (r=-0.17 to -0.15).ConclusionAlmost all factors improved in the early phase (3–6 months) after baseline assessment, while ER and IR ROM at shoulder level continued to improve long term.     

Dry needling for the management of thoracic spine pain

Abstract

Thoracic spine pain is as disabling as neck and low back pain; however, it has not received as much attention as the cervical and lumbar spine in the scientific literature. Among the different structures that can refer pain to the thoracic spine, muscles often play a relevant role. In fact, myofascial trigger points (TrPs) from several neck, shoulder and spinal muscles can induce pain in the region of the thoracic spine. There is a lack of evidence reporting the presence of myofascial TrPs in the thoracic spine, but clinical evidence suggests that TrPs can be a potential source of thoracic spine pain. The current paper discusses the role of myofascial TrPs in the thoracic spine and summarises the proper and safe application of dry needling (DN) for the management of myofascial TrPs in two main spinal muscles involved in thoracic spine pain: the thoracic multifidi and longissimus thoracis. In addition, this paper discusses the application of DN in other tissues such as tendons, ligaments and scars.     

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.