Evaluating pelvic rotator strength: Investigating asymmetry and its correlation with pelvic rotation angle during active straight leg raise.

Abstract

Background: Although lumbopelvic rotation control muscle is important to maintain pelvic neutral alignment during active straight leg raise (ASLR), pelvic rotator strength has not been evaluated. Thus, a novel method is needed to measure pelvic rotator strength and to determine whether pelvic rotator muscle asymmetry is related to side difference in transverse plane pelvic rotation angle (TrPRA) during ASLR.

Objective: To find average pelvic rotator strength, verify the reliability of pelvic rotator strength measurement method, and identify the correlation between pelvic rotator strength asymmetry and side difference in TrPRA during ASLR.

Methods: Forty healthy participants were enrolled. Pelvic rotator strength was measured using a hand-held dynamometer. TrPRA was measured using a smart KEMA motion sensor. Reliability was analyzed using intraclass correlation coefficient (ICC). The correlation between pelvic rotator strength asymmetry and side difference in TrPRA during ASLR was analyzed using Pearson's correlation coefficient.

Results: The average pelvic rotator strength was 120.3 N (72.9-202.2) for males and 94.4 N (58-125.8) for females. The reliability of pelvic rotator strength measurement demonstrated good to excellent intra- (ICC = 0.87-0.97) and inter-rater (ICC = 0.93-0.98) values. A significant moderate relationship existed between pelvic rotator strength asymmetry and side difference in TrPRA during ASLR (r = 0.39, p < 0.05).

Conclusion: The pelvic rotator muscle strength measurement method can be clinically used with good to excellent intra- and inter-rater reliability. Pelvic rotator strength asymmetry should be considered to evaluate and manage the pelvic rotation control during ASLR.