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- Title
Bending the Elbow During Shoulder Flexion Facilitates Greater Scapular Upward Rotation and a More Favorable Scapular Muscle Activation Pattern.
- Authors
Rabin, Alon; Tabi, Brakha R.; Uhl, Timothy L.; Kozol, Zvi
- Abstract
Context: Decreased scapular upward rotation (UR) and diminished activation of the serratus anterior (SA) and lower trapezius (LT) are often observed among patients with subacromial impingement syndrome. Maintaining the elbow fully flexed during shoulder flexion may limit glenohumeral motion due to passive insufficiency of the triceps brachii and therefore facilitate greater scapular UR and increased scapular muscle activation. Objectives: To compare scapular UR, SA, upper trapezius (UT), middle trapezius, and LT activation levels between shoulder flexion with the elbow extended (Flexion-EE) to shoulder flexion with the elbow fully flexed (Flexion-EF). This study hypothesized that Flexion-EF would result in greater scapular UR, greater SA and LT activation, and a lower UT/SA and UT/LT activation ratio compared with Flexion-EE. Design: Cross-sectional study. Setting: A clinical biomechanics laboratory. Participants: Twenty-two healthy individuals. Main Outcome Measures: Scapular UR and electromyography signal of the SA, UT, middle trapezius, and LT, as well as UT/SA and UT/LT activation ratio were measured during Flexion-EE and Flexion-EF. Results: Flexion-EF resulted in greater scapular UR compared with Flexion-EE (P < .001). Flexion-EF resulted in greater S A activation, lower UT activation, and a lower UT/SA activation ratio compared with Flexion-EE (P< .001). Conclusions: Fully flexing the elbow during shoulder flexion leads to increased scapular UR primarily through greater activation of the SA. This exercise may be of value in circumstances involving diminished scapular UR, decreased activation of the SA, and an overly active UT such as among patients with subacromial impingement syndrome.
- Subjects
ELBOW physiology; SHOULDER physiology; TRAPEZIUS muscle physiology; PATHOLOGICAL laboratories; STATISTICS; SERRATUS anterior muscles; RANGE of motion of joints; MUSCLE contraction; CROSS-sectional method; MEASUREMENT of angles (Geometry); SCAPULA; ROTATIONAL motion; SIGNAL processing; DESCRIPTIVE statistics; ELECTROMYOGRAPHY; DATA analysis; DATA analysis software; PATIENT positioning
- Publication
Journal of Sport Rehabilitation, 2022, Vol 31, Issue 2, p146
- ISSN
1056-6716
- Publication type
Article
- DOI
10.1123/jsr.2021-0116