In order to obtain joint-specific baseline strength characteristics in older adults, clinicians and researchers must have knowledge regarding the relative stability of the various strength tests (the strength difference between repeated measures) and the number of prebaseline practice sessions required to obtain consistent data. To address these needs, the relative multiple-test stability and reliability associated with lower extremity isokinetic and 1-repetition-maximum (1RM) strength measures were assessed in a sample of older adults (N = 30, 65.2 ± 6.3 years), over 4 weeks (T1-T4). Isokinetic ankle plantar-flexion (30°/s) strength and 1RM ankle plantar-flexion, leg-press, and knee-flexion strength exhibited poor stability between Weeks T1 and T2 but stabilized between Weeks T2 and T3 and Weeks T3 and T4. The measures exhibited low incidence of injury and induced low levels of residual muscle soreness. Findings suggest that the 1RM measures require at least 1 prebaseline training session in order to establish consistent baseline performance and are more reliable than isokinetic ankle plantar-flexion tests.
The authors are with the Musculoskeletal Biomechanics Research Laboratory, Dept. of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA 90033.