Older adults experience declines in muscle mass and strength that can lead to the development of mobility limitations. Power also plays a role in mobility, as the strength to perform a movement is useless, if the movement cannot be performed at a functional velocity.
PURPOSE: The purpose of the study was to determine which isokinetic angular velocity was best for relating power to functional performance as measured by chair rise time and Long Distance Corridor Walk (LDCW) speed.
METHODS: Eight male and 15 female community-dwelling older adults (age 76.3 ± 8.0 yrs; BMI 25.47 ± 3.16 kg•m-2) at risk of mobility limitations (classified by strength-to-weight ratio <1.71 Nm•kg-1 in males, <1.34 Nm•kg-1 in females) performed unilateral knee extension on an isokinetic dynamometer at 60, 180, and 300°•s-1 and power was measured at each velocity. Subjects performed the LDCW by walking 10 laps of a 20 m course (400 m total) at the fastest pace they were able to maintain. Chair rise time was found by standing unassisted from a chair 5 times as fast as possible. The relationship between variables was found via Pearson correlations.
RESULTS: Power at all knee extension angular velocities was related to LDCW speed. This relationship was strongest at 300°•s-1 (r = 0.63, P<0.01), but was also significant at 180°•s-1 (r = 0.57, P<0.01) and 60°•s-1 (r = 0.47, P<0.05). The relationship between power and chair rise time was not significant.
CONCLUSION: Knee extension power at 300°•s-1 was most related to walking speed. Chair rise time was not significantly related to knee extension power. It may be better to measure power rather than strength when screening older adults for risk of mobility limitations.
Supported by: NIH Grant 1R15 A6040700-01A1