Enhanced fatigue resistance in older adults during repeated sets of intermittent contractions.

Reportedly, muscle fatigue in older individuals is greater, less than, or similar to young individuals, potentially because of differences in muscle groups studied, type of contraction, continuous vs. intermittent contractions, exercise duration, duty cycle, and contraction speed. During a single set of isokinetic mode knee extensions, muscle fatigue is similar between older and younger individuals. However, repeated sets may favor the more oxidative nature of muscle from older adults and may be necessary to reveal age-associated enhanced fatigue resistance. The purpose of this investigation was to compare muscular fatigue induced by repeated sets of intermittent isokinetic mode knee extensions in older and younger males. Nineteen older (mean +/- SD) (66 +/- 6 yr) and 16 younger (21 +/- 2 yr) men completed 5 sets of 30 isokinetic mode knee extensions at 180 degrees/second. In the analysis of absolute fatigue, both groups significantly decreased torque production during each set, with young men having significantly higher torque production during all 5 sets. Relative fatigue was significantly greater in young participants during sets 2 through 5 (old vs. young: set 2: 17.1 vs. 26.6%; set 3: 25.5 vs. 39.7%; set 4: 28.1 vs. 45.1%; set 5: 29.3 vs. 46.4%; overall relative fatigue: old 22.2%; young 38.1%). These data indicate enhanced fatigue resistance in older men, which was revealed using repeated sets of intermittent contractions. Resistance to muscle fatigue is only one component of healthy aging muscle, and perhaps exercise interventions targeted toward prevention of falls in the elderly should focus on improved muscle power rather than fatigability/sustainability of contractions.