Assessment of lower extremity muscle power in functionally-limited elders

Background and aims: 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. Methods: 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. Results: 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 (R-2=0.636). Conclusions: These findings support the reliability and concurrent validity of MP for the evaluation of muscle power in older individuals.