Affiliations: [a] Department of Physical Therapy and Rehabilitation
Sciences, The University of Kansas Medical Center, Kansas City, KS, USA | [b] Department of Orthopedic Surgery, The University of
Kansas Medical Center, Kansas City, KS, USA
Note: [] Address for correspondence: Wen Liu, Ph.D., Department of
Physical Therapy and Rehabilitation Sciences, University of Kansas Medical
Center, 3901 Rainbow Blvd, Kansas City, KS 66160-7601, USA. Tel.: +1 913 588
6799; Fax: +1 913 588 4568; E-mail: wliu@kumc.edu
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.
