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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #203324
Title: Does force or velocity contribute more to maximal muscle power in older adults?

Author
item CLARK, DAVID - HNRCA AT TUFTS
item PATTEN, CAROLYNN - VA PALO ALTO HEALTH CARE
item REID, KIERAN - HNRCA AT TUFTS
item PHILLIPS, EDWARD - SPAULDING REHABILITATION
item Fielding, Roger

Submitted to: American College of Sports Medicine
Publication Type: Proceedings
Publication Acceptance Date: 11/30/2006
Publication Date: 6/1/2007
Citation: Clark, D.J., Patten, C., Reid, K.F., Phillips, E.M., Fielding, R. Does force or velocity contribute more to maximal muscle power in older adults?. In: American College of Sports Medicine, May 31, 2007, New Orleans, Lousiana.39(S5):262.

Interpretive Summary:

Technical Abstract: Muscle power, the product of force and velocity, has been found to be more sensitive than strength for predicting functional status in older adults. Some investigators therefore advocate the use of high velocity contractions during resistance training to target power. However, the relative contributions of force and velocity to power remain unclear and are critical to explaining age-related decline in motor performance. PURPOSE To investigate how age-related decrements in force and velocity contribute to muscle power. METHODS Participants included 13 healthy middle-aged adults (age 40-55, 5 male), 12 healthy older adults (age 70-85, 9 male), and 5 older adults at risk for mobility disability (age 70-85, 2 male, SPPB ' 9). EMG was acquired during five maximal effort knee extensions of the dominant leg under three conditions: 1) power measured against a resistance of 25 Nm, 2) isometric MVC torque at 60 degrees of knee flexion, 3) velocity at 40% 1RM. Torque, velocity and EMG were averaged for each dynamic trial between 40 and 60 degrees of knee flexion. Isometric MVC torque was averaged over a 500ms window surrounding peak torque. For all data the mean of trials 2-4 was used for analysis. RESULTS Power, MVC, and velocity were similar between middle-aged and older healthy groups, but the older at-risk group demonstrated significant (p<.05) impairment of power (52% less), MVC (28% less) and velocity (39% less). Despite similar group means for all variables in the middle-aged and older healthy groups, step-wise regression analysis revealed that velocity explained more of the variance in power, especially for the older adults. While MVC predicted 50% of the variability in power for the middle-aged group, it explained only 37% in the older group. Adding velocity to the model explained an additional 33% of the variability in the young group (83% total), and 54% in the older group (90% total). Evaluated across all subjects, agonist muscle activation was strongly correlated with velocity (r=.62, p<.0001), while antagonist co-contraction was not (r=.24, p=.19). CONCLUSION Peak muscle power in older adults is dominated by movement velocity rather than force. Age-related declines in muscle velocity are strongly associated with deficits in agonist muscle activation.