Muscle Mitochondrial Capacity Is Impaired Immediately Following Maximal Exercise

This study measured the time course mVO2max following both maximal and submaximal exercise. Healthy male and female participants were tested (n = 12 maximal and n = 8 submaximal exercise). A NIRS device was placed on the left medial gastrocnemius. Participants performed either one minute of maximal, rapid (~2 Hz), or submaximal (~0.37 Hz) plantar flexion exercise on a custom pneumatic ergometer. mVO2max was measured before and immediately after exercise. mVO2max measurements consisted of four incomplete recovery curves of muscle metabolism taken after 30 seconds of electrical muscle stimulation except in the first post-exercise trial. The four recovery curves were collected 50-, 156-, 260-, and 366-seconds post-exercise, each producing a mVO2max rate constant. After maximal exercise muscle acceleration decreased to 52 + 18% (p = 0.001) of pre-values. mVO2max was reduced from the pre-exercise mean at the first post-trial (2.16 + 0.44 min-1 to 1.21 + 0.52 min -1, p < 0.001). The fourth trial showed recovery from the first (2.2 + 0.46 min-1 vs 1.21 + 0.52 min-1, p < 0.001) and was not significantly different from pre-exercise values (2.2 + 0.46 min-1 vs 2.16 + 0.44 min-1, p = 0.41). No change in acceleration or mVO2max was seen after submaximal exercise (p > 0.05). The 56.7% reduction in mVO2max supports the hypothesis that in young, healthy individuals a minute of maximal exercise transiently impairs mVO2max which then recovers within six minutes. The NIRS method shows promise in tracking time course changes in mVO2max and warrants further investigation of the transient effects of exercise on mVO2max.