Abstract
A standardized protocol for assessing trunk rotational strength symmetry has not been established. Opposing muscle (agonist/antagonist) strength ratios have been used to assess strength asymmetry of appendicular joints but not the asymmetry of trunk rotational strength. The purpose of this study was to develop a protocol for measuring isometric trunk rotational strength with proper data analysis to assess rotational strength asymmetry.
Methods: Maximum isometric trunk rotational strength of twenty healthy young adults, 12 women (25.1 ± 3 years), 8 men(30.1 ± 5.6 years), was measured at 5 positions of trunk rotation on two different days by two different testers. Strength asymmetry was assessed in several ways including F-tests, percent-differences, and strength ratios.
Results: Trunk strength was symmetrical at neutral and 18° testing positions. In the 36° pre-rotated trunk positions, right contractions toward neutral tended to be stronger than left contractions; whereas left contractions away from neutral tended to be stronger than right contractions.
Conclusions: Our findings suggest caution when interpreting asymmetry at the 36° pre-rotated position. These methods of testing and assessing rotational strength asymmetry may be useful in patient populations in which strength asymmetry is hypothesized.