|Pojednic, Rachele M.|
|Clark, David J.|
|Phillips, Eddie M.|
|Fielding, Roger A.|
Submitted to: Journal of Aging and Physical Activity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2012
Publication Date: 8/1/2012
Citation: Pojednic, R., Clark, D., Patten, C., Reid, K., Phillips, E., Fielding, R. 2012. The specific contributions of force and velocity to muscle power in older adults. Journal of Aging and Physical Activity. 47(8):608-613. Interpretive Summary: Muscle power is now acknowledged as a valuable measure for quantifying age-related impairments in muscle and has also been shown to be a valuable indicator of functional limitation in older adults. Power is defined as work performed over a period of time, or as the product of force and movement velocity. Because power reflects both force production and movement velocity, age-related physiological impairments affecting either one or both factors will contribute to declines in power and potentially to declines in physical function. The objective of this study was to investigate the relative contributions of force production and movement velocity on muscular power and functional ability in middle aged, older healthy, and older mobility limited adults. It was hypothesized that the dynamic component of power may make it a more sensitive indicator than static strength assessments for detecting age-related impairments in functional capacity. Indeed, declines in movement velocity, but not strength, were found to be significantly associated with declines in power due to aging. Additionally, movement velocity, but not strength, was determined to be associated with declines in functional outcomes such as stair climbing and rising from a chair. These findings demonstrate that movement velocity is an increasingly important determinant of maximal power output with advancing age and functional ability. Velocity is also a critical component of functional outcomes with aging and may contribute to functional deficits. This helps to explain why the rate-dependent variable power has emerged as a critical component of both assessment and rehabilitation of muscular performance and physical function in older adults.
Technical Abstract: This study investigates relative contributions of force and velocity on muscular power and function in middle-aged (MH), older healthy (OH), and older mobility-limited (OML) adults. Seventy-nine men and women underwent tests including leg muscle power at 180deg/sec (SPisok), isometric maximal torque (STisok), maximal contraction velocity at 40% 1-RM (V40%1RM), Short Physical Performance Battery (SPPB), multiple chair rise and stair climb. STisok was associated with SPisok in MH (P=0.0045). Both STisok (p=0.001) and V40%1RM (p=0.007) were associated with SPisok in OH. V40%1RM was associated with SPisok in OML (p=0.02). V40%1RM demonstrated an effect on multiple chair rise time in OH and OML (p=0.028, p=0.0008) not MH (p=.71), and stair climb time in OML (p=.022), not MH or OH (p=0.42, p=0.23). Movement velocity is an important determinant of power output with age and functional ability. Velocity is also a critical component of functional outcomes with aging and may contribute to functional deficits.