Reliability of isometric muscle endurance tests in subjects with postural neck pain

Objective: The purpose of this study was to determine the reliability of 3 isometric muscle endurance tests in subjects with postural neck pain. Methods: Twenty-one subjects with chronic postural neck pain performed 3 submaximal muscle tests twice on the first occasion and once at the second session 3 days later. The tests examined isometric neck flexion, neck extension, and scapular muscle endurance. Results: Reliability was excellent for the neck flexor test (intraclass correlation coefficient [ICC] = 0 93), moderate for the scapular test (ICC = 0.67), and good for the neck extensor test (ICC = 0 88). The standard error of measure for the tests was 6.4, 10.9, and 25.9 seconds, respectively. The minimum change required to represent real change in muscle endurance was 17.8 seconds for the neck flexor test, 30.1 seconds for the scapular test, and 71.3 seconds for the neck extensor test. Conclusion: This study showed the reliability of 3 cervical spine and shoulder girdle submaximal muscle endurance tests in patients with postural neck pain.