The Difference in Output Properties Between Dominant and Nondominant Limbs as Measured by Various Muscle Function Tests

Abstract

Recently, right and left output properties exerted from specific muscle groups have been evaluated using special measurement devices such as an isokinetic dynamometer. However, it remains unclear whether the coach can properly evaluate muscle function corresponding to lateral specificity in athletes. This study aimed to examine the different output properties between the dominant (D) and nondominant (ND) upper limbs as measured by muscle function tests with various muscle contraction patterns. Fifteen right-handed young men participated in this study. Each subject carried out isometric, isokinetic, and isotonic muscle power tests by elbow flexion with right and left arms. When calculating the laterality index, the laterality of the isotonic test (1.17) was the highest. In all tests, significant correlations were found between the measurements of the D and ND limbs. The isometric test was the highest (r = 0.93), followed by the isokinetic test (r = 0.66-0.83) and the isotonic test (r = 0.55). To examine the ratio of the laterality of measurements provided by each muscle function test, each measurement was converted to a standard score (Z-score). There were significant differences between D and ND limbs in the isometric (D:ND = 55.0:45.0) and the isotonic (54.1:45.9) tests but not in the isokinetic test (60°·s⁻¹, 51.4:48.6; 180°·s⁻¹, 50.7:49.2; 300°·s⁻¹, 51.8:48.2). Particularly, the D (right) limb exerted greater muscle power in the isometric and the isotonic tests than in the isokinetic test. Occupational therapists or strength and conditioning professionals should understand that the D-ND differences shown by these muscle function tests may differ because of measurement conditions.