Comparing Bilateral Muscular Imbalance Ratios In The Upper Extremities

Abstract

Muscular imbalances may increase the risk of injury and decrease physical performance. Conventional wisdom suggests dominant side musculature may be more developed owing to preferred usage. Quantifying muscle imbalance between non- dominant and dominant arms is facilitated by technology that permits the measurement of arm power output across a range of resistances. PURPOSE: To compare power output achieved by the dominant and non-dominant arms under various load conditions. METHODS: 18 females and 14 males (21.0 ± 2.3 years, 66.9 ± 4.3 inches, 168.3 ± 36.2 lbs) were enrolled into an optimal muscle loading program using Proteus (Proteus Motion, USA). Each subject performed the following ten movements: abduction, adduction, external rotation, internal rotation, biceps curl, triceps extension, horizontal push, horizontal row, vertical push, and vertical row. Each movement was repeated twice under four separate loads: 7lb, 14lb, 21lb, and 28lb. Maximum average power for each movement was recorded in watts for further analysis. A paired-samples t-test, under the 28lb condition, was used to determine the relationship between the mean power of all subjects’ dominant versus non-dominant arms. Repeated measures ANOVA was run to then determine differences in mean powers. RESULTS: Power achieved in all movements was similar (r values ranged from 0.723-0.954; p<0.001) at the 28 lb load. On average, an individual’s dominant arm during abduction produced less power than the non-dominant arm (143.6 ± 63.5 watts compared to 127.7 ± 50.2; p=0.050). However, external rotation of the dominant arm tended to generate more than non-dominant arms (p=0.053). Correlation values close to 1.00 across all comparisons demonstrated the variance between arms was minimal. The results of the ANOVA showed no statistical differences between arms. CONCLUSIONS: The current assumption that dominant limbs are capable of greater power may not be true in all planes and when tested with isotonic loads applied in three-dimensional space. Our subjects did not demonstrate power imbalances between dominant and non- dominant arms.