Near infrared spectroscopy-derived muscle oxidative capacity correlates to oxidative metabolic predictors of performance in highly trained female middle-distance runners.

Investigate the relationship between muscle oxidative capacity, indices of O2 metabolism (maximal capacity and sustainable steady state), and severe domain performance in highly trained female middle-distance runners. Incremental treadmill test determined maximal oxygen uptake (V̇O2max) and lactate turn point (LTP). Critical speed (CS) was calculated from historical race and training data. Time-to-exhaustion (TTE) trials were run at a speed predicted to elicit exhaustion in 4 min. Muscle oxidative capacity (rectus femoris) was measured via muscle oxygen uptake (mV̇O2) from near infrared spectroscopy (NIRS) deoxygenation slopes during intermittent arterial cuff occlusions (8 × 5 s ON/5 s OFF) following light exercise. Slopes were fit to a mono-exponential model to calculate recovery rate (k). Muscle oxidative capacity was highly correlated to V̇O2max (r = 0.71, p = 0.002), LTP (r = 0.67, p = 0.005), and estimated CS (r = 0.66, p = 0.005). However, muscle oxidative capacity was not correlated to TTE performance (r = 0.13, p = 0.622). NIRS-derived muscle oxidative capacity is strongly associated with maximal and sustainable oxidative metabolic rates in highly trained female runners but appears independent of the finite energy capacity required during a severe-domain performance.