A comparison of scapulothoracic muscle electromyographic activity in subjects with and without subacromial impingement syndrome during a functional task

Normal values of scapular muscle activity ratio during arm elevation and the relationship to muscle strength and sex difference

BACKGROUND

The normal value of the scapular muscle activity ratio during arm elevation is not clear.

OBJECTIVE

To obtain normal values of the scapular muscle activity ratio during arm elevation in healthy individuals.

METHODS

This cross-sectional study enrolled 47 healthy people. The participants performed shoulder flexion and lowered task with 90-degree movements every 2 seconds. Muscle activities of scapular muscles were measured. For normalization, the maximum isometric contraction of the shoulder flexion was measured at 90∘ (reference contraction). The integrated electromyographic value (IEMG) obtained during the task was normalized by IEMG during the reference contraction and the relative IEMG value was calculated. Then, the scapular muscle activity ratio was computed. The relationship between muscle strength and other factors was also investigated.

RESULTS

The median values for upper trapezius/serratus anterior and upper trapezius/lower trapezius were often approximately 1, and that for upper trapezius/middle trapezius was often between 1 and 2. The shoulder flexion isometric strength and scapular muscle activity ratio showed significant negative correlations in multiple phases.

CONCLUSION

Normal values for upper trapezius/serratus anterior and upper trapezius/lower trapezius during arm elevation and lowering were generally 1. Low muscle strength may contribute to an abnormal scapular muscle activity balance.

Kinematic, electromyographic and isokinetic measurements for the management of shoulder subacromial pain syndrome: A systematic review

BACKGROUND

Subacromial shoulder pain syndrome is a very common and challenging musculoskeletal disorder. Kinematics, electromyographic muscle activity and isokinetic dynamometry are promising non-invasive movement analysis tools to improve understanding of this condition. No review has combined their results to provide a better understanding of the effects of subacromial pain syndrome on shoulder movement. This systematic review aimed to synthesise the associations between exposure to shoulder pain due to subacromial pain syndromes or subacromial impingement and changes in shoulder movement measures.

METHODS

The databases were Scholar google, Pubmed, Science Direct, Scopus and the Cochrane Library. We included studies that observed the association of the presence of subacromial pain syndromes or subacromial impingement with changes in shoulder motion measures.

FINDINGS

Seventeen studies with 943 participants were included. The main kinematic change was a lower scapular posterior during abduction in the subacromial pain syndrome group with a "low" level of evidence (standardised mean difference = -0.61, 95% confidence interval [-0.80; -0.43]). The main electromyographic change was an earlier onset of activation of the upper trapezius in the subacromial pain syndrome group, with a "moderate" level of evidence (standardised mean difference = 1.01, 95% confidence interval: [-2.97; 0.96]). The main isokinetic change was a lower peak internal rotator torque in the subacromial pain syndrome group, with a 'low' level of evidence (standardised mean difference = -0.41, 95% confidence interval: [-0.53; -0.29]).

INTERPRETATION

The variables measured during movement are associated with subacromial pain syndrome or subacromial impingement syndrome. Consistency between the results supports the importance of scapula biomechanics measurements in these conditions.

Function, strength, and muscle activation of the shoulder complex in Crossfit practitioners with and without pain: a cross-sectional observational study

BACKGROUND

The shoulder joint is the most commonly injured joint in CrossFit practitioners, because of the high intensity and loads associated with this sport. Despite the large number of clinical cases, there is a shortage of studies that investigate influence of biomechanical aspects of upper limbs' injuries on CrossFit practitioners. This study hypothesized that there would be a difference in function, strength, and muscle activation between Crossfit practitioners with and without shoulder pain.

METHODS

We divided 79 Crossfit practitioners into two groups according to whether they reported pain (n = 29) or no pain (n = 50) in the shoulder during Crossfit training. Muscle function, strength, and activation were assessed using the Disability Arm, Shoulder and Hand function questionnaire, Upper Quarter Y Balance Test and Closed Kinetic Chain Upper Extremity Stability Test shoulder tests, isometric muscle strength assessment by manual dynamometry and muscle activation by surface electromyography and pain report.

RESULTS

The function based on questionnaire was associated with pain (p = 0.004). We observed a statistically significant difference between the two groups only in the surface electromyography activity of the lower trapezius, and in the variables of shoulder pain and function (p = 0.038).

CONCLUSION

Crossfit practitioners with shoulder pain occurring during training showed good function and stability of the shoulder joint, but there was a reduction in the activation of stabilizing muscles, especially the lower trapezius. Trial registration Registro Brasileiro de Ensaios Clinico (Brasilian National Registry) with the ID: RBR-2gycyv.

Three-dimensional kinematic analysis of upper limb movements between individuals with and without subacromial shoulder pain exploring the statistical parametric mapping

Subacromial shoulder pain (SSP) accounts for 44-65% of all cases of shoulder pain. Kinematic alterations in the upper limbs have been observed in individuals with SSP, although there is no consensus on such alterations in the literature. Therefore, the present study aimed to compare the three-dimensional kinematics of the scapula, trunk, and arm during shoulder flexion-extension and abduction-adduction movements in individuals with SSP and a control group using statistical parametric mapping (SPM). We evaluated 117 participants [61 with SSP and 56 in the control group (CG)]. The three-dimensional kinematic analysis was performed starting from arm extension/adduction (0%), moving to flexion/abduction, and ending returning to extension/adduction, respectively (100%) in both groups. SSP group flexed more their trunk (0-100%, p < 0.001) and rotated scapula internally (0-20%, p < 0.001 and 75-100%, p < 0.001); rotated upwards (17-32%, p < 0.005 and 58-87%, p < 0.003) and posteriorly tilted (28-79%,p < 0.001 and 81-95%,p < 0.006) less than CG group during arm abduction-adduction. Through arm flexion-extension, the SSP group flexed (38-82% p < 0.009) less their trunk, rotated upwards (5-10% p = 0.021) less their scapula, and posteriorly tilted scapula (0-100% p < 0.001) more than CG. Combining conventional variables used to describe motion in individuals with SSP, such as minimum and maximum values, range of motion, and results provided by SPM can furnish a detailed description of the compensations and limitations of the patient, enabling a better understanding of the function of the scapular girdle as well as improvements in the evaluation process and clinical decision making.

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

BACKGROUND

Shoulder 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.

METHOD

This 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.

RESULTS

Results 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.

CONCLUSION

It was concluded that the shoulder pain of the women evaluated caused changes in the activity of the anterior and middle deltoid muscles.

The effect of dry needling & muscle energy technique separately and in combination in patients suffering shoulder impingement syndrome and active trigger points of infraspinatus

OBJECTIVE

The aim of this study was to investigate the effects of a combination of dry needling (DN) and muscle energy technique (MET) on pain intensity (PI), pressure pain threshold (PPT) and shoulder active range of motion (ROM) in patients with shoulder impingement syndrome and active trigger points in the infraspinatus muscle.

METHODS

39 patients, aged 20-50 participated in this study. All the cases were randomly assigned into three groups: group 1 (n = 13) received DN, group 2 (n = 13) received MET, and group 3 (n = 13) received DN & MET. The patients were treated for three sessions in a one-week period with at least a two-day break between sessions.

RESULTS

The results showed a significant improvement in visual analog scale (VAS), PPT and shoulder ROM over time (P < 0.001) in all three groups. There were no significant differences BETWEEN VAS (P = 0.406) PPT (P = 0.293), external rotation(EXT.ROT) (0.476), internal rotation (INT.ROT)(P = 0.476) and extension(EXT) (P = 0.574) ROMs in the three groups; however, DN group was significantly more effective on abduction(ABD) (P = 0.003) and flexion(FLEX) (0.012) ROM compared with other two groups.

CONCLUSION

In line with previous studies, the present study found that the application of DN, MET and combined of these treatment on active trigger points in the infraspinatus muscle of patients with shoulder impingement syndrome helps reduce pain, increase PPT and enhance the shoulder ROM. Both techniques are effective in the treatment of trigger points. Nevertheless, DN is more effective in enhancing the ROM of flexion & abduction.

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

BACKGROUND

Little 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.

METHODS

Twenty-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.

FINDINGS

There 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).

INTERPRETATION

Compared 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.