Assessment of lower extremity muscle power in functionally-limited elders

Abstract

The purpose of this study was to assess the reliability and concurrent validity of a new methodology to evaluate lower extremity muscle power in older, functionally limited men and women. A cross sectional evaluation was performed on 58 older men (n=27) and women (n=31) (74.2+/-0.9 years). Knee and hip (leg press) and knee extensor power were evaluated on pneumatic and isokinetic resistance equipment. Incremental single attempt power (IP) testing utilized a single attempt at attaining maximum power at each of six external resistances and was compared to multiple attempt pneumatic power (MP) testing determined by the highest of 5 attempts at achieving maximum power at two set resistances and also with power determined by isokinetic dynamometry. Leg press extension MP yielded significantly greater power than IP at both low (mean=225.3+/-11.85 and 183.9+/-11.52 watts respectively, p<0.001) and high (mean=249.7+/-15.25 and 201.7+/-13.18 watts respectively, p<0.001) external resistances. Knee extension MP also produced significantly greater power when compared to IP at low (mean=82.4+/-4.45 and 69.7+/-4.28 watts respectively, p<0.001) and high (mean=93.7+/-6.3 and 83.2+/-5.93 watts respectively, p<0.001) external resistances. MP testing exhibited excellent reliability at both low (leg press extension: Intra Class Correlation (ICC)=0.93, knee extension: ICC=0.87) and high (Leg press extension: ICC=0.85, Knee Extension: ICC=0.91) external resistances. MP knee extension at 70% 1 RM also showed good agreement with average isokinetic power (R2=0.636). These findings support the reliability and concurrent validity of MP for the evaluation of muscle power in older individuals.