Email updates

Keep up to date with the latest news and content from BMC Sports Science, Medicine and Rehabilitation and BioMed Central.

Open Access Highly Accessed Research

Shoulder muscle endurance: the development of a standardized and reliable protocol

Jean-Sébastien Roy12*, Bryan Ma3, Joy C MacDermid34 and Linda J Woodhouse356

Author Affiliations

1 Centre for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec City, Quebec, Canada

2 Department of Rehabilitation, Faculty of Medicine, Laval University, Quebec City, Quebec, Canada

3 School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada

4 Hand and Upper Limb Centre, St. Joseph's Health Centre, London, Ontario, Canada

5 Department of Surgery, Holland Orthopaedic & Arthritic Hospital of Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

6 Departments of Rehabilitation and Orthopaedics, Hamilton Health Sciences, Hamilton, Ontario, Canada

For all author emails, please log on.

Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology 2011, 3:1  doi:10.1186/1758-2555-3-1

Published: 11 January 2011

Abstract

Background

Shoulder muscle fatigue has been proposed as a possible link to explain the association between repetitive arm use and the development of rotator cuff disorders. To our knowledge, no standardized clinical endurance protocol has been developed to evaluate the effects of muscle fatigue on shoulder function. Such a test could improve clinical examination of individuals with shoulder disorders. Therefore, the purpose of this study was to establish a reliable protocol for objective assessment of shoulder muscle endurance.

Methods

An endurance protocol was developed on a stationary dynamometer (Biodex System 3). The endurance protocol was performed in isotonic mode with the resistance set at 50% of each subject's peak torque as measured for shoulder external (ER) and internal rotation (IR). Each subject performed 60 continuous repetitions of IR/ER rotation. The endurance protocol was performed by 36 healthy individuals on two separate occasions at least two days apart. Maximal isometric shoulder strength tests were performed before and after the fatigue protocol to evaluate the effects of the endurance protocol and its reliability. Paired t-tests were used to evaluate the reduction in shoulder strength due to the protocol, while intraclass correlation coefficients (ICC) and minimal detectable change (MDC) were used to evaluate its reliability.

Results

Maximal isometric strength was significantly decreased after the endurance protocol (P < 0.001). The total work performed during the last third of the protocol was significantly less than the first third of the protocol (P < 0.05). The test-retest reliability of the post-fatigue strength measures was excellent (ICC >0.84).

Conclusions

Changes in muscular performance observed during and after the muscular endurance protocol suggests that the protocol did result in muscular fatigue. Furthermore, this study established that the resultant effects of fatigue of the proposed isotonic protocol were reproducible over time. The protocol was performed without difficulty by all volunteers and took less than 10 minutes to perform, suggesting that it might be feasible for clinical practice. This protocol could be used to induce local muscular fatigue in order to evaluate the effects of fatigue on shoulder kinematics or to evaluate changes in shoulder muscle endurance following rehabilitation.