Axial rotation strength in seated neutral and prerotated postures of young adults.

Abstract

To determine the trunk-twisting capability from neutral and prerotated postures, a study was designed to measure torque generated in isometric and isokinetic activities of 50 young adults. To determine the isometric and isokinetic axial rotation strengths of male and female subjects in neutral and asymmetric postures and to quantify the effect of velocity of rotation on the isokinetic trunk strength profile. A specially designed axial rotation tester was employed using specially written modular software for data collection and analysis. The isometric strengths were measured in neutral, 15 degrees, and 30 degrees prerotated trunk postures. The isokinetic strength was measured in activities starting from the neutral position to fully rotated and from a fully rotated position to neutral positions at 10 degrees, 20 degrees, and 40 degrees per second angular velocity. The data obtained were subjected to multivariate and univariate analyses of variances with multiple comparisons and multiple regression analyses. All study participants were significantly stronger in isometric twisting activities than in the isokinetic activities. In isometric activities, participants were 20-25% weaker in prerotated postures when twisting in the direction of prerotation and were approximately 30% stronger in the opposite direction. For isokinetic activities, the trunk rotation from neutral to asymmetric positions produced lesser torques compared with torques from rotated positions to the neutral position. The torque-producing capability declined with increasing velocity of activity. This study adds to the data base of rotational strength.