Muscle oxygenation in vastus lateralis and gastrocnemius during incremental running exercise: effect of exercise intensity, VO2max, sex and age

Introduction. The aim of this study was to describe the effect of exercise intensity, maximum oxygen utilisation (V ̇O_2MAX), sex and age on vastus lateralis (VL) and gastrocnemius (Gn) muscle oxygenation measured using near-infrared spectroscopy (NIRS) during incremental running exercise to exhaustion, in a participant group having a large range of V ̇O_2MAX.Methods. Systemic cardiorespiratory responses (V ̇O_2, ventilatory thresholds), and variables of muscle oxygenation (Δ[HHb], Δ[O2Hb], ΔTSI) at VL and Gn muscles were collected continuously in thirty-six participants (11 women, 25 men; age: 34.110.7 yr; height: 1.750.1 m; weight: 70.216.6 kg; weekly training: 591374 min;) during an incremental running test (V ̇O_2MAX=52.511.9 mL·min-1·kg-1). Breakpoint analyses were used to compare systemic cardiorespiratory responses and patterns of muscle oxygenation. The effect of exercise intensity, V ̇O_2MAX, sex and age on Δ[HHb], Δ[O2Hb] and ΔTSI at VL and Gn were determined at 10% increments from 50% to 100% of V ̇O_2MAX.Results. The only predictor of V ̇O_2MAX was Δ[HHb] at VL, and gas exchange thresholds and muscle oxygenation breakpoints were not significantly correlated. There were no effects of V ̇O_2MAX or sex on the dynamics of muscle oxygenation. The effect of exercise intensity was significant for all variables at VL, and only for Δ[HHb] at Gn at 50% and 60% of V ̇O_2MAX. The magnitude of muscle oxygenation responses was significantly decreased in women compared to men, and there was no effect of age. Conclusion. Our results indicate that using NIRS oximetry, Δ[HHb] on vastus lateralis, but not gastrocnemius, is suitable to identify changes in exercise intensity and aerobic capacity in running, with a lower magnitude of response in women compared to men, and with no effect of age.<br>