Skeletal muscle mitochondrial function in endurance athletes measured with near infrared spectroscopy

The purpose of this experiment was to determine if near-infrared spectroscopy (NIRS) measurements of muscle oxidative capacity could detect the known differences between endurance trained athletes (N=6) and inactive subjects (N=7). Muscle oxygen consumption (mVO2) was measured during brief arterial occlusions. The recovery of mVO2 after electrical stimulation was fit to an exponential curve, with the time constant (Tc) used as an index of mitochondrial capacity. Tc values for endurance trained were 18.3 2.3 and 19.2 1.6 seconds, whereas inactive controls were 31.6 5.1 and 33.1 3.5 seconds, for the shallow and deep channels respectively (p < 0.001 for comparison between groups). The magnitude of the differences in muscle oxidative capacity between endurance trained and inactive subjects matched literature values, supporting the use of the NIRS method to measure muscle oxidative capacity.