The Application of Double Elastic Band Exercise in the 90/90 Arm Position for Overhead Athletes

Comparative Electromyographic Study of Scapular Stabilizing Muscles During Five Main Rehabilitation Exercises

OBJECTIVE

The aim of the study is to compare the surface electromyographic amplitude, activation ratio, and onset latency of the main scapular stabilizing muscles between five typical rehabilitative exercises.

DESIGN

Twenty-seven healthy participants performed five scapular exercises (wall slide, wall push-up plus, prone horizontal abduction with external rotation, external rotation in side lying, and low row) while simultaneously recording surface electromyographic of serratus anterior, middle trapezius, lower trapezius, and upper trapezius. Surface electromyographic amplitudes, onset latencies, and activation ratios were calculated.

RESULTS

Prone horizontal abduction with external rotation showed an excellent upper trapezius/middle trapezius (0.43) and upper trapezius/lower trapezius (0.30) muscle balance with high (>50% maximum voluntary isometric contraction) middle trapezius and lower trapezius amplitudes, a low (<20% maximum voluntary isometric contraction) upper trapezius amplitude, and an early activation of the scapular stabilizing muscles (-474.7 to 89.9 ms) relative to upper trapezius. External rotation in side lying showed excellent upper trapezius/serratus anterior (0.26), upper trapezius/middle trapezius (0.32), and upper trapezius/lower trapezius (0.21) activation ratios and, along with low row and wall slide, showed early activation of the scapular stabilizing muscles (-378.1 to -26.6 ms).

CONCLUSIONS

Prone horizontal abduction with external rotation presented optimal scapular neuromuscular control. Although external rotation in side lying, low row, and wall slide did not meet all the criteria associated with optimal scapular neuromuscular control, these exercises could be used in early stages of shoulder rehabilitation because they favor early activation of the scapular stabilizing muscles.

Effect of Scapular Retraction on Lower Trapezius, Infraspinatus, and Deltoid Muscle Electromyographic Activity During the Side-Lying Abduction Exercise

Background

The lower trapezius (LT) muscle, which stabilizes the scapula posteriorly during arm elevation, has been interesting to both clinicians and researchers for its importance in throwing-related shoulder rehabilitation and injury prevention.

Purpose

The purpose of this study was to investigate the electromyographic activity of the LT and other relevant muscles during scapular and shoulder activities in the side-lying position.

Methods

Twenty collegiate baseball players volunteered to participate in this study. Electromyographic (EMG) output of the lower trapezius, infraspinatus, posterior deltoid, middle deltoid, serratus anterior, and upper trapezius muscles were collected. All the subjects performed isometric resistance exercises in four arm positions: 0° horizontal abduction from the coronal plane (NEUT) with protraction (NEUT-PRO), 15° horizontal adduction from the coronal plane (HADD) with protraction (HADD-PRO), and NEUT with retraction (NEUT-RET), and HADD-RET in a side-lying isometric abduction exercise with two external loads: a 9.1 kg dumbbell and 40% of the manual muscle test (MMT). The subjects also performed two more isometric resistance exercises: supine protraction and side-lying external rotation (ER) of the glenohumeral (GH) joint in GH adduction at 90° of GH ER or with as much ER as possible. All raw EMG data were normalized to maximal voluntary isometric contraction (% MVIC) of the corresponding muscle.

Results

LT activity was significantly greater in HADD-RET with 9.1 kg than that of HADD-PRO (p < 0.001) (55 vs 21% MVIC) while middle deltoid muscle activity was significantly decreased in both NEUT and HADD-RET compared to that of NEUT and HADD-PRO (p < 0.001). In contrast, IS muscle activity was significantly increased in HADD-RET with 9.1 kg compared with that 40% MMT (p < 0.001) (41 vs 22% MVIC).

Conclusion

LT activity was modulated by changes in scapulothoracic and glenohumeral joint positioning during a side-lying isometric abduction exercise. These findings may help clinicians to select exercises to improve scapular muscle balance ratios during rehabilitation of the shoulder complex.

Level of Evidence

Level 3b, Controlled laboratory study.

A comparison of teres minor and infraspinatus muscle activation in the prone position

Background

Methods

Results

Conclusion

Examining Muscle Activity Differences During Single and Dual Vector Elastic Resistance Exercises

BACKGROUND

Elastic resistance exercise is a common part of rehabilitation programs. While these exercises are highly prevalent, little information exists on how adding an additional resistance vector with a different direction from the primary vector alters muscle activity of the upper extremity.

PURPOSE

The purpose of this study was to examine the effects of dual vector exercises on torso and upper extremity muscle activity in comparison to traditional single vector techniques.

STUDY DESIGN

Repeated measures design.

METHODS

Sixteen healthy university-aged males completed four common shoulder exercises against elastic resistance (abduction, flexion, internal rotation, external rotation) while using a single or dual elastic vector at a fixed cadence and standardized elastic elongation. Surface electromyography was collected from 16 muscles of the right upper extremity. Mean, peak and integrated activity were extracted from linear enveloped and normalized data and a 2-way repeated measures ANOVA examined differences between conditions.

RESULTS

All independent variables differentially influenced activation. Interactions between single/dual vectors and exercise type affected mean activation in 11/16 muscles, while interactions in peak activation existed in 7/16 muscles. Adding a secondary vector increased activation predominantly in flexion or abduction exercises; little changes existed when adding a second vector in internal and external rotation exercises. The dual vector exercise in abduction significantly increased mean activation in lower trapezius by 25.6 ± 8.11 %MVC and peak activation in supraspinatus by 29.4 ± 5.94 %MVC (p<0.01). Interactions between single/dual vectors and exercise type affected integrated electromyography for most muscles; the majority of these muscles had the highest integrated electromyography in the dual vector abduction condition.

CONCLUSION

Muscle activity often increased with a second resistance vector added; however, the magnitude was exercise-dependent. The majority of these changes existed in the flexion and abduction exercises, with little differences in the internal or external rotation exercises.

LEVEL OF EVIDENCE

3b.

Electromyography activity of the teres minor muscle with varying positions of horizontal abduction in the quadruped position

Background

The teres minor (TMi) muscle exposed relatively high activity during the acceleration and deceleration phases of the throwing motion, compared with the infraspinatus muscle. However, few studies have identified TMi muscle activity in intervention exercises. The purpose of this study was to investigate TMi muscle activities in different horizontal adduction positions in the quadruped horizontal abduction exercise. This study hypothesized that TMi muscle activity would differ in response to resistance application across different horizontal adduction positions.

Materials and methods

Nineteen collegiate baseball players volunteered their participation. Raw electromyography activity of the TMi muscle along with 7 different muscles attached to the scapula on the dominant-side were collected, and normalized by each of the corresponding maximum voluntary isometric contractions. All subjects performed manual isometric resistance horizontal abduction exercises at 90° and 135° of abduction with 3 horizontal adduction angles in the quadruped position: 1) coronal, 2) scapular, and 3) sagittal plane. Electromyography data were also collected from rhythmical concentric contraction of horizontal abduction at 90° of abduction in the quadruped position.

Results

TMi muscle activity was significantly greater with the arm positioned in the coronal plane than that of the scapular and sagittal planes (41, 26, and 17% maximum voluntary isometric contraction, respectively) (P < .05).

Conclusion

The present study demonstrated that TMi muscle activity varied depending on horizontal adduction positions.