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This study compared the strength of the knee extension and flexion muscles in groups of young and elderly women under two conditions: eccentric exercise in which the muscles were lengthened while subjects tried to resist an external force, versus concentric contractions in which the muscles shortened. Twenty-six females, aged 20 to 29 (Mean 25 +/- 3 SD), and 26 elderly women, aged 66 to 89 (Mean 73 +/- 6 SD), were tested at two angular velocities of movement, 45 degrees and 90 degrees/s, on a KinCom isokinetic dynamometer. Elderly women had significantly lower peak and average torque values in all comparisons with the young female group (25 to 54% lower, p less than .01). However, differences between the age groups were consistently smaller for the eccentric type of muscle action than the concentric, in both knee extensors and flexors.
Vandervoort et al. (Sun,) studied this question.