The relationship between muscle oxygen saturation kinetics and maximal blood lactate accumulation rate across varying sprint cycle durations

This study evaluated the relationship between muscle oxygen saturation (SmO2) and the maximal blood lactate accumulation rate (vLamax) during three test durations (10, 15 and 30 s) to validate the optimal test duration of vLamax protocol. Thirteen developmental trained males (age: 27 +/- 6 years and peak power: 1133 +/- 185W and 14.88 +/- 1.61 W<middle dot>kg(-)(1)) performed three maximal cycle tests (10, 15 and 30 s). Performance metrics were measured throughout; peak power, mean power, and cadence. vLamax was determined using blood lactate concentrations following each test. SmO2 of the vastus lateralis was measured using a MOXY device via near-infrared spectroscopy, throughout all experimental conditions. The shortest test (10 s) produced a significantly (p = 0.005; p < 0.001) higher vLamax (0.83 +/- 0.15 mmol<middle dot>L--(1)<middle dot>s(-)(1)) than 15 s (0.67 +/- 0.13 mmol<middle dot>L--(1)<middle dot>s(-)(1)) and 30 s (0.43 +/- 0.06 mmol<middle dot>L--(1)<middle dot>s(-)(1)). Three relationships between SmO2 kinetics and vLamax were observed: (1) a very strong inverse relationship (r = -0.994, p < 0.001) between SmO2 desaturation and vLamax time dependent kinetics, (2) a significant inverse relationship (r = -0.648, p < 0.001) between SmO2 time spent at the nadir and vLamax and (3) a moderate relationship (r = 0.508, p = 0.11) and similar time to attain the SmO2 nadir (8.47 +/- 1.50s) and vLamax (8.92 +/- 0.77s). These results validate the 10-s test duration for determination of vLamax verified with mathematical modelling predicting peak vLamax occurs at similar to 9 s. SmO2 desaturation closely reflects the vLamax kinetics, with the time points of the SmO2 nadir and peak vLamax closely corresponding.