Analysis of Scapular Muscle EMG Activity During Elastic Resistance Oscillation Exercises From the Perspective of Different Arm Positions

Abstract

Background: Little is known about the optimal exercise intensity and the effects of arm position on elastic resistance exercise. The purpose of this study was to investigate scapular muscle activity in different arm positions utilized during standing elastic resistance exercise. Hypothesis: Lower trapezius (LT), serratus anterior (SA), and infraspinatus (IS) muscle activity will vary across arm positions above shoulder level. Also, oscillation resistance exercise will result in increased muscle activity compared with isometric contraction. Study Design: Controlled laboratory study. Level of Evidence: Level 4. Methods: A total of 19 uninjured male collegiate baseball players volunteered to participate in this study. The electromyography (EMG) activity of the LT, upper trapezius (UT), middle deltoid (MD), SA, and IS muscles was determined using surface EMG in 3 arm positions: diagonal pattern 1 (D1), 120° of shoulder abduction (120), and 90° shoulder abduction with external rotation and elbow flexion (90/90) during both isometric contraction and oscillation resistance exercise. Results: No difference in EMG activity of the LT muscle was found between the 120 and 90/90 position. However, the 120 position increased UT and MD muscle activity significantly more than those of the 90/90 position. The D1 arm position significantly increased SA muscle activity more than the 120 and 90/90 positions while the LT muscle activity was nearly silent. Conclusion: The standing 90/90 position effectively generated both LT and IS muscle EMG activity while minimizing both UT and MD muscle activity. Clinical Relevance: The use of oscillation movements under elastic loading can create high muscle activation in the LT muscle without an adverse effect of the humeral head position and scapular rotation.

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

“…Both ISO and OSC exercises were used with an elastic band (Green CLX, 2.1 kg at 100% elongation; TheraBand; Performance Health) at 40% elongation (single band). 28 The athletes were also given another elastic band (Blue CLX, 2.6 kg at 100% elongation; TheraBand) at 40% elongation on the distal portion of the arm directly above the elbow (double band). The players oscillated the distal aspect of their upper extremity in the 90/90 arm position while externally rotating the shoulder and releasing the externally rotated shoulder to the original position at a constant pace following a cue from a metronome set at 150 beats per minute.…”

“…The players oscillated the distal aspect of their upper extremity in the 90/90 arm position while externally rotating the shoulder and releasing the externally rotated shoulder to the original position at a constant pace following a cue from a metronome set at 150 beats per minute. 28 To identify the intensity of the elastic resistance exercises, the amount of MVIC force (N•m) of ER was measured in the 90/90 arm position using a handheld dynamometer (MicroFET; Hoggan Scientific, LLC) for each participant in the standing position prior to the exercise protocol. The examiner applied maximal resistance to the distal portion of the pronated forearm on the participant's dominant side to create shoulder internal rotation while holding the elbow joint with the other hand.…”

“…he modulation of infraspinatus (IS) muscle activity has been identified in a variety of intervention exercises for injury prevention. [1][2][3]9,24,28 However, professional tennis players present with IS atrophy syndrome to which the cause is uncertain. 31 Another shoulder external rotator muscle, the teres minor (TMi) muscle, generates up to 45% of external rotation (ER) force compared with the IS muscle.…”

“…29 Previous studies have measured periscapular muscle activities in intervention exercises with a therapeutic elastic band. 12,20,28 The elastic band can minimize the activity of the upper trapezius (UT) and middle deltoid (MD) muscles as it utilizes the tension of elongation with less gravity effect. 28 No study has yet investigated TMi and LT muscle activities in different scapular planes using the elastic band.…”

“…12,20,28 The elastic band can minimize the activity of the upper trapezius (UT) and middle deltoid (MD) muscles as it utilizes the tension of elongation with less gravity effect. 28 No study has yet investigated TMi and LT muscle activities in different scapular planes using the elastic band. Therefore, the purpose of this study was to compare the modulation of TMi and LT muscle activity using elastic resistance between the frontal and scapular planes during the standing position with double elastic band application and oscillation movement (OSC).…”