Scapular Muscle Activation at Different Shoulder Abduction Angles During Pilates Reformer Arm Work Exercise

Abstract

Background and Objectives: Scapular muscles are crucial in controlling scapular movement, ensuring proper alignment, and preventing injuries during shoulder joint motion. The shoulder abduction angle is one of the most important factors when performing exercises to improve scapular movement control. The Pilates reformer arm work (AW) movement can be performed with different shoulder abduction angles. Therefore, this study analyzed the differences in scapular muscle activation depending on the shoulder abduction angle during the AW movement. Materials and Methods: Twenty-six healthy adult males performed the AW movement under four shoulder abduction angle conditions (0°, 90°, 135°, 160°). When performing the AW in the four conditions, surface electromyography analyzed the muscle activation of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), serratus anterior (SA), posterior deltoid (PD), and levator scapulae (LS), and the muscle activation ratios of the UT/LT, LS/LT, UT/SA, and LS/SA. Results: The UT, LT, and SA muscle activation increased proportionally with the increasing shoulder abduction angle (p < 0.001). The LT showed the highest muscle activity at the shoulder abduction angle of 135° (p < 0.001). The MT and PD showed the highest muscle activities at the shoulder abduction angle of 90° (p < 0.001). The muscle activity ratios of the UT/LT and LS/LT were the lowest at the shoulder abduction angles of 90° and 135° (p < 0.001). The muscle activity ratio between the UT/SA and LS/SA was the lowest at the 135° and 160° shoulder abduction angles (p < 0.001). Conclusions: Our findings highlight the impact of the shoulder abduction angle on scapular muscle activation, suggesting that different angles may be used to engage specific muscles during Pilates reformer arm work exercises selectively. This insight can guide exercise interventions for individuals aiming to improve their scapular control and stability.

Keywords: Pilates reformer arm work; electromyography; scapular muscle; shoulder abduction.

Figure 1

Pilates reformer arm work (AW) exercises. (a) Starting position, (b) performing position for AW0, (c) performing position for AW90, (d) performing position for AW135, (e) performing position for AW160.

Figure 2

The mean (standard deviation) scapular muscle activity (%MVIC) at each arm position angle (0°, 90°, 135°, and 160°) and in concentric (a), isometric (b), and eccentric (c) phases during AW. Color shading of the bars corresponds to the shoulder abduction angle (0°: blue; 90°: green; 135°: burgundy; 160°: orange). On the X-axis, the plane of scapular muscles is represented as follows: UT, upper trapezius; MT, middle trapezius; LT, lower trapezius; SA, serratus anterior; PD, posterior deltoid; LS, levator scapulae. The lettering scheme is used to denote significantly different means (p < 0.05). * Conditions that showed a significant difference from 0° AW angle; ^† conditions that showed a significant difference from 90° AW angle; ^§ conditions that showed a significant difference from 135° AW angle.

Figure 3

The mean (standard deviation) scapular muscle activity ratio at each arm position angle (0°, 90°, 135°, 160°) during AW. Color shading of the bars corresponds to the shoulder abduction angle (0°: blue; 90°: green; 135°: burgundy; 160°: orange). On the X-axis, the plane of scapular muscles is represented as follows: UT, upper trapezius; LT, lower trapezius; SA, serratus anterior; LS, levator scapulae. The lettering scheme is used to denote significantly different means (p < 0.05). * Conditions that showed a significant difference from 0° AW angle; ^† conditions that showed a significant difference from 90° AW angle; ^§ conditions that showed a significant difference from 135° AW angle.