Low- or high-intensity strength training partially restores impaired quadriceps force accuracy and steadiness in aged adults

Abstract

Because many daily tasks are executed at only a fraction of maximal strength, an understanding of submaximal force control may be important for improving function in aged adults. We compared the effects of low- and high-intensity (LI and HI, respectively) strength training on maximal and explosive strength and on the accuracy (force error) and steadiness (variability) of submaximal quadriceps force in elderly humans. Older subjects (age, 72 years; n = 27) had 57% lower maximal strength in comparison with young subjects (age, 21 years; n = 10). Older subjects had 190% (19 N), 50% (1 N), and 80% (4 N) more force error in matching 25 N of quadriceps force during eccentric, isometric, and concentric contractions, and had 157%, 0%, and 60% more variability in these forces compared with young subjects. Force error and force variability were correlated with each other but not with maximal strength. Thirty sessions of LI (n = 9 participants) or HI (n = 9 participants) training of equal total work increased maximal strength in the older subjects by 29%. Training also significantly reduced force error and variability--by 31% and 30%, respectively--of eccentric and concentric contractions. A control group of older subjects (n = 9) showed no significant changes in any variables. LI or HI strength training was equally effective in partially restoring elderly adults' maximal strength and control of submaximal force.