Richard W. Bohannon and Kimberly Pratt
Richard W. Bohannon and Jason Smutnick
Motion of the femur and pelvis during hip flexion has been examined previously, but principally in the sagittal plane and during nonfunctional activities. In this study we examined femoral elevation in the sagittal plane and pelvic rotation in the sagittal and frontal planes while subjects flexed their hips to ascend single steps. Fourteen subjects ascended single steps of 4 different heights leading with each lower limb. Motion of the lead femur and pelvis during the flexion phase of step ascent was tracked using an infrared motion capture system. Depending on step height and lead limb, step ascent involved elevation of the femur (mean 47.2° to 89.6°) and rotation of the pelvis in both the sagittal plane (tilting: mean 2.6° to 9.7°) and frontal plane (listing: mean 4.2° to 11.9°). Along with maximum femoral elevation, maximum pelvic rotation increased significantly (p < .001) with step height. Femoral elevation and pelvic rotation during the flexion phase of step ascent were synergistic (r = .852–.999). Practitioners should consider pelvic rotation in addition to femoral motion when observing individuals’ ascent of steps.
Richard W. Bohannon and A. Williams Andrews
Overall muscle strength of extremities is often characterized by measurements from one or more selected actions. This study evaluated the legitimacy of that procedure. Measurements obtained by handheld dynamometry from 13 muscle actions of 156 apparently healthy individuals (50–79 years) were subjected to correlational analysis, principal-components analysis, and cluster analysis. The isometric strengths of all muscle actions correlated significantly with one another (r = .506–.965). Principal-components analysis without rotation showed that all tested actions loaded highly on overall limb muscle strength. Principal-componcnis analysis with varimax rotation revealed high loadings that were grouped by extremity (upper vs. lower). Ankle dorsiflexion strengths were exceptions. These findings, in conjunction with the cluster analysis, support using one or more actions to characterize isometric limb muscle strength among the elderly but suggest that muscle strength in an upper or lower extremity is best characterized by an action (e.g., elbow flexion) of that extremity.