Analysis of phase detects altered timing of muscle activation in subjects with chronic shoulder pain.

Optimal exercise therapy for shoulder pain is unknown due to limited information regarding specific changes in muscle function associated with pain. Timing of muscle activity with respect to movement (phase) can provide information about muscle activation patterns without requiring electromyography data normalization which is problematic in the presence of pain. The aim of this study was to determine if a phase measure is able to detect differences in the timing of shoulder muscle activation in subjects with chronic shoulder pain. Fourteen subjects with pain and 14 without pain were recruited. Electromyography from eight shoulder muscles was recorded. Approximately 20 cycles of small amplitude (∼30°) rapid shoulder flexion/extension was performed. A cross-correlation and spectrographic analysis provided a measure of phase. Welch's t-tests were used to compare mean phase angles between groups. Subjects with chronic shoulder pain had greater variability in the relative timing of muscle activation with significant differences found in the phase angles for pectoralis major, infraspinatus, supraspinatus, upper and lower trapezius and serratus anterior. This preliminary study indicates that the examination of the timing of muscle activation using a phase measure can identify significant differences in muscle function between normal subjects and those with chronic shoulder pain.

Shoulder muscle activation patterns and levels differ between open and closed-chain abduction.

OBJECTIVES: Open and closed-chain abduction of the shoulder are commonly used in rehabilitation and exercise programs to assess and/or improve shoulder muscle function. However, it is not known if shoulder muscle activation patterns differ between these two exercises. Therefore the purpose of this study was to compare muscle activation patterns during closed-chain shoulder abduction performed using a shoulder press machine with open-chain abduction using free weights. DESIGN: Experimental study. METHODS: Open and closed-chain abduction were performed by 15 and 14 subjects respectively at low (25%), medium (50%) and high (75%) load. Surface and indwelling electrodes were used to record the activation pattern of seven shoulder muscles during the concentric phase of each exercise. Data were normalised to maximum voluntary contractions (MVC), time normalised and compared over the common range of motion (40°-140° abduction). RESULTS: Only the activation pattern of middle deltoid had a strong positive correlation between exercises (r≥0.65, p<0.05) with similar activation levels at all loads (35%, 50% and 60% MVC, p=1.0). All other muscles tested had inconsistent, low or negative correlations between exercises. Significantly lower average activation levels were recorded during closed-chain abduction for subscapularis at all loads, upper trapezius at medium and high loads and infraspinatus and lower trapezius at high load (p <0.05). CONCLUSIONS: Open-chain abduction is required to facilitate the stabilising role of the rotator cuff and axioscapular muscles, in response to middle deltoid activity. Closed-chain exercises may enable full range shoulder abduction earlier in rehabilitation programs, with an inherent stability and less demand on the rotator cuff.

Is subscapularis recruited in a similar manner during shoulder internal rotation exercises and belly press and lift off tests?

OBJECTIVES: Although the belly press and lift off tests are recommended to assess subscapularis function, shoulder internal rotation (IR) exercises performed in other shoulder positions are more commonly used to restore subscapularis function. It is not known if shoulder IR exercises specifically activate subscapularis to the same degree as the lift off and belly press tests, and thus have the potential to effect subscapularis strength gains. Therefore, the aim was to compare subscapularis activation levels with those of other shoulder internal rotator muscles during the belly press and lift off tests and shoulder IR exercise positions. DESIGN: Original research. METHODS: Twenty asymptomatic volunteers performed maximal isometric contractions during the belly press and lift off tests and shoulder IR performed at 90° and 0° abduction in an upright position and supported at 90° abduction in supine. Muscle activation levels were recorded using a combination of indwelling and surface electrodes. Data were normalized to maximum voluntary contractions and averaged. RESULTS: Moderate average subscapularis activation levels were recorded during all shoulder IR tasks examined with no significant difference between tasks (p=0.18). The belly press test was the only IR task in which subscapularis activation levels were significantly higher than all other shoulder internal rotator muscles (p<0.05). CONCLUSIONS: Shoulder IR exercises activate subscapularis to similar moderate levels as the belly press and lift off tests and therefore, have similar potential to strengthen subscapularis. However, the belly press test, with significantly higher subscapularis activation than other shoulder internal rotators, more specifically targets subscapularis.

Does load influence shoulder muscle recruitment patterns during scapular plane abduction?

OBJECTIVES: Load is used to increasingly challenge muscle function and has been shown to increase muscle activity levels with no change in activation patterns during shoulder flexion, extension, adduction and rotation. However, the effect of load during shoulder abduction, a movement commonly used in assessment of shoulder dysfunction and to improve shoulder function, has not been comprehensively examined. Therefore, the purpose of this study was to determine if load influences shoulder muscle activation patterns and levels during scapular plane abduction in normal subjects. DESIGN: Experimental study. METHODS: Fourteen volunteers performed shoulder abduction in the scapular plane at 25%, 50% and 75% of maximum load. Eight shoulder muscles were investigated using a combination of indwelling and surface electromyographic recordings: middle deltoid, infraspinatus, subscapularis, supraspinatus, serratus anterior, upper and lower trapezius and rhomboid major. RESULTS: All muscles tested showed increasing average muscle activation levels with increasing load and strong correlations in the activation patterns between loads. CONCLUSIONS: Increasing shoulder abduction load not only increases activity in middle deltoid but also in the rotator cuff (infraspinatus, subscapularis, supraspinatus) and axioscapular (serratus anterior, upper and lower trapezius, rhomboid major) muscles. The functional stabilising role of both the rotator cuff and axioscapular muscles is considered an important contribution to the increased activation levels in these muscle groups as they function to counterbalance potential translation forces produced by other muscles during shoulder abduction. The activation patterns of all shoulder muscle groups during abduction can be trained at low load and progressively challenged with increasing load.

Does changing the plane of abduction influence shoulder muscle recruitment patterns in healthy individuals?

STUDY DESIGN: Observational laboratory study. BACKGROUND: Abduction is a movement commonly used in the assessment of shoulder dysfunction and prescription of exercises to improve shoulder function. Abduction in the scapular and coronal planes are used interchangeably. It is not known if the activation of individual shoulder muscles differ between abduction performed in these planes and therefore, if they represent different tests/exercises. OBJECTIVE: To quantify and compare the muscle activation patterns and levels for each shoulder muscle during abduction performed in the scapular plane with that performed in the coronal (scapular -30°) and scapular +30° planes. METHODS: Electromyographic recordings were taken from eight shoulder muscles of fourteen healthy volunteers during shoulder abduction in the scapular and coronal planes and in a plane 30° anterior to the scapular plane (scapular +30°) at 50% of maximum load. RESULTS: Similar average muscle activation levels were demonstrated during abduction in the scapular plane and within a 30° arc of this plane for all muscles except: middle deltoid (5% MVC higher activation in the coronal and 4% MVC lower activation in the scapular +30° plane) and upper trapezius (6% MVC lower activation in the scapular +30° plane). Activation patterns between planes for all muscles were similar (ICC(3,1) ≥ 0.87). CONCLUSIONS: Abduction can be performed within a 30° arc of the scapular plane with no change in shoulder muscle activation patterns. Only middle deltoid activation levels change between the scapular and coronal planes and middle deltoid and upper trapezius between the scapular and scapular +30° planes.

An Arabic version of the effort-reward imbalance questionnaire: translation and validation study.

An Arabic version of the Effort-Reward Imbalance Questionnaire was developed and validated through a translation process with cross-cultural considerations. The translated questionnaire was evaluated for reliability and validity. A Principal Components Analysis was conducted following assessment of the suitability of data for factor analysis. Components with high eigenvalues were extracted, followed by Varimax rotation. Three components with eigenvalues greater than 1.0 (50% of variance) were indicated. The analysis showed Cronbach's alpha coefficients of .82 for the Effort scale, .88 for the Reward scale, and .74 for the Overcommitment scale. The test-retest reliability was high with intra-correlation coefficients of > or = .86. The Arabic version of the Effort-Reward Imbalance Questionnaire showed adequate reliability and validity and is a suitable instrument to assess work stress in Arabic-speaking people.

Associations among work-related stress, cortisol, inflammation, and metabolic syndrome.

This cross-sectional study examined the relationship between work-related stress, cortisol, and C-reactive protein (CRP) in predicting metabolic syndrome (MtS). Self-reported work stress measured by the effort reward imbalance ratio (ERI), anthropometric data, CRP, and saliva cortisol were collected from 204 healthy Jordanian male workers. ERI and cortisol were significantly associated with the presence of MtS (OR = 4.74, 95% CI: 2.13-10.55; OR = 3.03, 95% CI: 2.08-4.40; OR = 11.50, 95% CI: 2.16-59.14, respectively). The odds of MtS in men with high ERI and high cortisol were significantly higher than that of men with low ERI and low cortisol (OR = 11.50, 95% CI: 2.16-59.14). CRP was significantly associated with MtS (OR = 2.51, 95% CI: 1.50-4.20). The odds of MtS were significantly higher in centrally obese men with both high ERI and CRP level. Thus, high ERI along with high cortisol or high CRP increases the risk for MtS, especially among centrally obese men.

Rotator cuff muscles perform different functional roles during shoulder external rotation exercises.

The aim of this study was to compare activity in shoulder muscles during an external rotation task under conditions of increasing arm support to investigate whether changing support requirements would influence muscle recruitment levels, particularly in the rotator cuff (RC) muscles. Electromyographic recordings were collected from seven shoulder muscles using surface and indwelling electrodes. The dominant shoulder of 14 healthy participants were examined during dynamic shoulder external rotation performed at 90° abduction with the arm fully supported, partially supported, and unsupported. Linear regressions between arm support load and the averaged muscle activity across participants for each muscle showed infraspinatus predominantly contributing to rotating the shoulder whilst supraspinatus, deltoid, upper trapezius, and serratus anterior were predominantly functioning in support/stabilization roles. During dynamic shoulder external rotation in mid-range abduction, the RC muscles perform different functional roles. Infraspinatus is responsible for producing external rotation torque, supraspinatus is playing a larger joint stabilizer role, and subscapularis is contributing minimally to joint stability. The results also indicate that increasing support load requirements during an external rotation task may be a functionally specific way to retrain the stabilization function of axioscapular muscles. Manipulating joint stabilization requirements while maintaining constant rotational load is a novel method of investigating the differential contribution of muscles to joint movement and stabilization during a given task.

Does supraspinatus initiate shoulder abduction?

PURPOSE: It is commonly stated that supraspinatus initiates abduction; however, there is no direct evidence to support this claim. Therefore, the aims of the present study were to determine whether supraspinatus initiates shoulder abduction by activating prior to movement and significantly earlier than other shoulder muscles and to determine if load or plane of movement influenced the recruitment timing of supraspinatus. METHODS: Electromyographic recordings were taken from seven shoulder muscles of fourteen volunteers during shoulder abduction in the coronal and scapular planes and a plane 30° anterior to the scapular plane, at 25%, 50% and 75% of maximum load. Initial activation timing of a muscle was determined as the time at which the average activation (over a 25 ms moving window) was greater than three standard deviations above baseline measures. RESULTS: All muscles tested were activated prior to movement onset. Subscapularis was activated significantly later than supraspinatus, infraspinatus, deltoid and upper trapezius, while supraspinatus, infraspinatus, upper trapezius, lower trapezius, serratus anterior and deltoid all had similar initial activation times. The effects of load or plane of movement were not significant. CONCLUSIONS: Supraspinatus is recruited prior to movement of the humerus into abduction but not earlier than many other shoulder muscles, including infraspinatus, deltoid and axioscapular muscles. The common statement that supraspinatus initiates abduction is therefore, misleading.

Systematic nonlinear relations between joint mechanics and the neural reflex response with changes in stretch amplitude at the wrist.

The effects on both joint mechanics and the neural stretch reflex of changes in amplitude of stretch ranging from within the region of short range stiffness up to 3% of resting muscle length were quantified. The level of activation of the primary agonist was held constant but there was a small but systematic increase in activation of the other flexor and extensor muscles as stretch amplitude increased. The patterns of change with stretch amplitude in both the joint mechanics and stretch reflex properties were non-linear but systematic and were well described by power relationships that accounted for high proportions of variance. With an increase in stretch amplitude, joint stiffness, viscosity, damping ratio and natural frequency decreased. In parallel with these mechanical changes, the neural reflex coherence increased and the phase advance and gain decreased. Multiple regression analyses partitioned the variation in the joint mechanics that was attributable to the various factors and it was found that the variation of the mechanics was almost entirely attributable to the variation of the neural reflex gain, which accounted for 93% of the changes in the stiffness, viscosity and natural frequency and 82% of the changes in the damping ratio. It is concluded that joint mechanics are significantly affected by changes in the neural reflex gain.

The association between work stress and inflammatory biomarkers in Jordanian male workers.

The study aimed to establish the association of work stress, expressed as effort-reward imbalance (ERI), and C-reactive protein (CRP) in 152 healthy Jordanian male employees. Self-report work stress, anthropometric data, and blood for CRP analysis were collected. A significant correlation between ERI and CRP (r = 0.29, p < .01), and between waist circumference with CRP (r = 0.44, p < .01) was found. Central obesity explained most of the variance in CRP after controlling for various covariates, and ERI was not a significant predictor of CRP (ΔR2 = 0.02; ß = 0.15, p = .052). However, when only the centrally obese group was considered, ERI accounted for 5.0% of the variability in the CRP (ß = 0.24, p < .05). Results of this study confirm previous findings that obesity is significantly associated with CRP, and support the notion that higher ERI amongst obese workers is one small but significant predictor of increased levels of CRP.

An Arabic version of the perceived stress scale: translation and validation study.

BACKGROUND: The Perceived Stress Scale has been designed to measure the degree to which situations in a person's life are perceived as stressful. OBJECTIVE: The paper describes the development of an Arabic version of the Perceived Stress Scale. DESIGN: A translation process with cross-cultural considerations was employed to produce an Arabic version of the Perceived Stress Scale. SETTINGS: Participants were asked to complete the Arabic version Perceived Stress Scale twice in their homes. PARTICIPANTS: The Jordanian study population for the Arabic version Perceived Stress Scale validation consisted of 126 volunteers (74 male, 52 female). Ninety participants completed the scale twice (55 male, 35 female), of whom 58 were high schools teachers and 32 technical workers. Arabic was the first language of all participants and all gave informed consent. RESULTS: The Arabic version Perceived Stress Scale reliability and validity were evaluated. Prior to an exploratory factor analysis, the suitability of data for factor analysis was assessed with acceptable results. The exploratory factor analysis showed two factors with eigenvalues greater than 1.0 (45.0% of variance). The Cronbach's alpha coefficients were 0.74 (Factor 1), 0.77 (Factor 2) and 0.80 for the Arabic version Perceived Stress Scale overall. The test-retest reliability had an intra-correlation coefficient of 0.90. CONCLUSIONS: The Arabic version Perceived Stress Scale showed an adequate reliability and validity. Therefore, the Arabic Perceived Stress Scale is considered a suitable instrument to assess perceived stress in Arabic people.

An electromyographic study of parkinsonian swallowing and its response to levodopa.

BACKGROUND: Few studies have investigated the effect of levodopa on parkinsonian swallowing with findings thus far being equivocal. METHODS: We used surface electromyography and accelerometry to investigate submental and laryngeal muscle activation during swallowing in 14 parkinsonian subjects before and after levodopa and in 22 age-matched controls. Our aims were (1) to demonstrate the clinical utility of noninvasive electromyography, (2) to identify electromyographic features of parkinsonian swallowing, and (3) to investigate the effect of levodopa on parkinsonian swallowing. RESULTS: The parkinsonian group showed increased burst amplitudes and durations and increased swallow duration, clearing activity and latency between submental and laryngeal bursts (P < .05) and used more swallows than did controls to consume water boluses (P < .001). Levodopa decreased the latency between submental and laryngeal bursts (P < .05) but did not produce effects on individual muscle bursts. CONCLUSIONS: The clinical utility of electrophysiological and biomechanical methods of swallowing assessment was demonstrated. Levodopa tended to normalize the timing of the combined swallow response but not the activity of individual muscles.

Direction-specific recruitment of rotator cuff muscles during bench press and row.

Recent studies indicate that rotator cuff (RC) muscles are recruited in a reciprocal, direction-specific pattern during shoulder flexion and extension exercises. The main purpose of this study was to determine if similar reciprocal RC recruitment occurs during bench press (flexion-like) and row (extension-like) exercises. In addition, shoulder muscle activity was comprehensively compared between bench press and flexion; row and extension; and bench press and row exercises. Electromyographic (EMG) activity was recorded from 9 shoulder muscles sites in 15 normal volunteers. All exercises were performed at 20, 50 and 70% of subjects' maximal load. EMG data were normalized to standard maximal voluntary contractions. Infraspinatus activity was significantly higher than subscapularis during bench press, with the converse pattern during the row exercise. Significant differences in activity levels were found in pectoralis major, deltoid and trapezius between the bench press and flexion exercises and in lower trapezius between the row and extension exercises. During bench press and row exercises, the recruitment pattern in each active muscle did not vary with load. During bench press and row exercises, RC muscles contract in a reciprocal direction-specific manner in their role as shoulder joint dynamic stabilizers to counterbalance antero-posterior translation forces.

A comprehensive analysis of muscle recruitment patterns during shoulder flexion: an electromyographic study.

Although flexion is a common component of the routine clinical assessment of the shoulder the muscle recruitment patterns during this movement are not clearly understood making valid interpretation of potential muscle dysfunction problematic. The purpose of this study was to comprehensively examine shoulder muscle activity during flexion in order to compare the activity levels and recruitment patterns of shoulder flexor, scapular lateral rotator and rotator cuff muscles. Electromyographic (EMG) data were recorded from 12 shoulder muscles sites in 15 volunteers. Flexion was performed in standing in the sagittal plane at no load, 20%, and 60% of each subject's maximum load. EMG data were normalized to maximum values obtained during maximum voluntary contractions. Results indicated that anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, upper, and lower trapezius were activated at similar moderate levels. However, subscapularis was activated at low levels and significantly lower than supraspinatus and infraspinatus. Similar activity patterns across time were demonstrated in the muscles that produce flexion torque, laterally rotate the scapula, as well as supraspinatus and infraspinatus, and did not change as flexion load increased. The onset of activity in supraspinatus and anterior deltoid occurred at the same time and prior to movement of the limb at all loads with infraspinatus activity also occurring prior to movement onset at the medium and high load conditions only. Posterior rotator cuff muscles appear to be counterbalancing anterior translational forces produced during flexion and it would appear that supraspinatus is one of the muscles that consistently "initiates" flexion.

The rotator cuff muscles have a direction specific recruitment pattern during shoulder flexion and extension exercises.

A recent study has shown that posterior rotator cuff (RC) muscles are recruited at significantly higher levels than the anterior RC during shoulder flexion. It was proposed that the mechanism whereby the posterior RC muscles were providing shoulder stability during flexion was to counterbalance potential anterior humeral head translation caused by flexion torque producing muscles. This hypothesis implies that anterior RC activity should be higher than posterior RC activity during extension to prevent posterior humeral head translation. As the normal recruitment pattern of the RC during extension has not been established, the purpose of this study was to examine this hypothesis by comparing shoulder muscle activation levels and recruitment patterns during flexion and extension exercises. Electromyographic (EMG) activity was recorded from 9 shoulder muscles in 15 volunteers. Flexion and extension exercises were performed in prone at 20%, 50%, and 70% of each participant's maximal load. A repeated measures ANOVA was used to determine differences between exercises, muscles and loads, while Pearson's correlation analysis was used to relate mean EMG patterns. During extension subscapularis and latissimus dorsi were activated at higher levels than during flexion; during flexion, supraspinatus, infraspinatus, deltoid, trapezius, and serratus anterior were more highly activated than during extension. In addition, the pattern of activity in each muscle did not vary with load. These results support the hypothesis that during flexion and extension the RC muscles are recruited in a direction specific manner to prevent potential antero-posterior humeral head translation caused by torque producing muscles.

Does passive mobilization of shoulder region joints provide additional benefit over advice and exercise alone for people who have shoulder pain and minimal movement restriction? A randomized controlled trial.

BACKGROUND: Passive mobilization of shoulder region joints, often in conjunction with other treatment modalities, is used for the treatment of people with shoulder pain and minimal movement restriction. However, there is only limited evidence supporting the efficacy of this treatment modality. OBJECTIVE: The purpose of this study was to determine whether passive mobilization of shoulder region joints adds treatment benefit over exercise and advice alone for people with shoulder pain and minimal movement restriction. DESIGN: This was a randomized controlled clinical trial with short-, medium- and longer-term follow-up. SETTING: The study was conducted in a metropolitan teaching hospital. PATIENTS: Ninety-eight patients with shoulder pain of local mechanical origin and minimal shoulder movement restriction were randomly allocated to either a control group (n=51) or an experimental group (n=47). INTERVENTION: Participants in both groups received advice and exercises designed to restore neuromuscular control at the shoulder. In addition, participants in the experimental group received passive mobilization specifically applied to shoulder region joints. MEASUREMENTS: Outcome measurements of shoulder pain and functional impairment, self-rated change in symptoms, and painful shoulder range of motion were obtained at 1, 3, and 6 months after entry into the trial. All data were analyzed using the intention-to-treat principle by repeated-measures analyses of covariance. RESULTS: No statistically significant differences were detected in any of the outcome measurements between the control and experimental groups at short-, medium-, or longer-term follow-up. LIMITATIONS: Therapists and participants were not blinded to the treatment allocation. CONCLUSION: This randomized controlled clinical trial does not provide evidence that the addition of passive mobilization, applied to shoulder region joints, to exercise and advice is more effective than exercise and advice alone in the treatment of people with shoulder pain and minimal movement restriction.

The role of shoulder muscles is task specific.

The aim of this study was to compare activity in shoulder muscles during unsupported internal and external rotation to examine their functional roles, and determine whether they retain their 'stabiliser' or 'mover' role regardless of the shoulder task. Electromyographic recordings in the dominant shoulder of 15 normal subjects were taken from 13 shoulder muscle sites using a combination of surface and intramuscular electrodes during isometric shoulder internal and external rotation in an unsupported abducted position under conditions of increasing load. During internal rotation significantly higher activity levels were found in subscapularis (p<0.001). During external rotation significantly higher activity levels were demonstrated in supraspinatus, infraspinatus, trapezius and serratus anterior (p<0.05). There were no significant differences in activity levels in deltoid, pectoralis major and latissimus dorsi during internal and external rotation. As rotational forces increased there was a significant increase in activity in all muscle sites activated above low levels (r(2)=0.93±0.07; mean±s.d.). This study has shown that shoulder muscle function is task specific and that shoulder muscle motor strategy for a particular task does not change with increasing torque. As the only shoulder rotators that demonstrated direction specificity the rotator cuff muscles are likely to be functioning to provide rotation torque while the deltoid is likely to be providing dynamic shoulder stability during the task examined. Higher scapulothoracic muscle activity during external rotation indicated the need for greater dynamic scapular stability as a result of higher rotator cuff activity during external than internal rotation.

Which is the optimal exercise to strengthen supraspinatus?

PURPOSE: Supraspinatus strengthening is an important part of shoulder rehabilitation programs. Because of the force-couple relationship between supraspinatus and deltoid during shoulder abduction, it has been proposed that the optimal exercise to strengthen supraspinatus is one that would maximize supraspinatus activity while minimizing surrounding muscle activity, particularly deltoid. The aim of this study was to simultaneously examine all exercises known to recruit supraspinatus at high levels and to compare the level of recruitment in supraspinatus, deltoid, and infraspinatus. METHODS: Using a combination of surface and intramuscular electrodes, EMG recordings were taken from supraspinatus, infraspinatus, and the three parts of deltoid of 15 subjects with normal dominant shoulder function during maximal isometric contractions in "empty can," "full can," prone elevation, pendant external rotation, and prone external rotation exercise positions. RESULTS: There was no significant difference in the level of supraspinatus activation for all exercise positions examined. No significant difference was found in activation levels across all muscles during the "can" exercise positions. The exercise positions using external rotation were found to activate parts of deltoid significantly less than the "can" and prone elevation positions. Infraspinatus was activated at greater levels than supraspinatus during the external rotation exercises. CONCLUSIONS: Using the criteria that the optimal exercise to strengthen supraspinatus should maximize supraspinatus activity while particularly minimizing deltoid activity, this study has shown that the pendant external rotation and prone external rotation exercises are more valid than the "can" and prone elevation exercises for supraspinatus strengthening in subjects with normal dominant shoulder function.

The 'empty can' and 'full can' tests do not selectively activate supraspinatus.

Based on previous electromyographic studies the 'empty can' (EC) and 'full can' (FC) tests have been promoted as being able to isolate activity to supraspinatus and are therefore diagnostic of supraspinatus dysfunction. However, there is evidence to suggest that these positions do not selectively activate supraspinatus, and that they may have poor diagnostic accuracy, bringing into question the validity of these tests. Due to limitations in the original EMG papers describing the EC and FC tests the current study aimed to further examine shoulder muscle activity during these tests to determine their ability to selectively activate supraspinatus. EMG activity was recorded from 13 muscles in 15 normal subjects while performing these two tests. Results showed that during the EC and FC muscle tests nine and eight other shoulder muscles, respectively, were equally highly activated as supraspinatus. It was concluded from these results that the EC and FC tests do not primarily activate supraspinatus with minimal activation from other shoulder muscles and therefore, do not satisfy basic criteria to be valid diagnostic tools for supraspinatus pathology. Therefore, these tests should not be interpreted as definitive tests for the clinical diagnosis of supraspinatus pathology. They may, however, be beneficial during shoulder muscle strengthening programs.