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Abstract
PURPOSE: The purpose of this study was to measure instantaneous muscle fatigue (IMF) in young and older adults while comparing IMF to mitochondrial capacity, endurance index (EI), and rate of muscle reperfusion. METHODS: 20 subjects (11 young and 9 older adults) were included in this study. IMF and EI were measured using data from twitch contractions collected from a tri-axial accelerometer. Reactive hyperemia test and muscle mitochondrial capacity were measured using near-infrared spectroscopy (NIRS). IMF measurement was done on two days to test for the reproducibility of the method and fatiguing exercise included two durations of calf raises. RESULTS: IMF was not different in young and older adults on both days. Mitochondrial capacity was lower in older adults compared with young adults. There was no relationship between IMF and EI; and reactive hyperemia measures for both groups. CONCLUSIONS: This study demonstrated comparable fatigue in young and old adults following both fatigue protocols. There was a 20% deficit in mitochondrial capacity in older adults compared to young adults which is consistent with previous studies. This study provided evidence of fatigue in both young and older adults.
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