Comparison of Shoulder Protraction Strength and Electromyography Activity of Serratus Anterior and Pectoralis Major in Subjects With or Without a Winged Scapula

J Sport Rehabil. 2019 Mar 1;28(3):272-277. doi: 10.1123/jsr.2018-0059. Epub 2018 Dec 6.

Abstract

Context: A winged scapula (WS) is associated with faulty posture caused by weakness of the serratus anterior (SA), which mainly acts as a scapular stabilizer muscle. It is important to accurately assess and train the SA muscle with a focus on scapula stabilizers during musculoskeletal rehabilitation of individuals with a WS.

Objective: The authors examined muscle activity in the SA and pectoralis major (PM), upper trapezius (UT), and anterior deltoid (AD) as well as shoulder protraction strength during isometric shoulder protraction in individuals with and without a WS.

Design: Cross-sectional study.

Setting: A clinical biomechanics laboratory.

Participants: In total, 27 males with no shoulder, neck, or upper-extremity pain participated.

Main outcome measures: Isometric shoulder protraction strength was collected and surface electromyography used to measure the activity of the SA, PM, UT, and AD muscles and selective SA activity ratio to other shoulder muscles.

Results: Electromyography activity of the SA muscle and shoulder protraction strength were significantly lower in individuals with a WS compared with the non-WS group (P < .05). In contrast, PM muscle activity and the PM-to-SA, UT-to-SA, and AD-to-SA ratios were significantly greater in individuals with a WS than in individuals without winging (P < .05).

Conclusions: Isometric shoulder protraction for measuring SA strength in individuals with a WS should focus on isolated muscle activity of the SA, and SA strengthening exercises are important for individuals with a WS.

Keywords: faulty posture; manual muscle testing; scapula stabilizer muscle; selective activation.

MeSH terms

  • Adult
  • Cross-Sectional Studies
  • Electromyography
  • Humans
  • Isometric Contraction
  • Male
  • Muscle Strength*
  • Pectoralis Muscles / physiology*
  • Posture
  • Scapula / anatomy & histology*
  • Shoulder / physiology*
  • Superficial Back Muscles / physiology*
  • Young Adult