Effects of prior heavy exercise on deoxygenation in deep versus superficial muscle regions during subsequent heavy exercise in adult males

We assessed the effects of prior heavy-intensity-exercise (PHE) on microvascular deoxygenation in deep vastus lateralis muscle (VLd) compared with the superficial VL (VLs). Thirteen subjects completed two 6-min bouts of heavy exercise, separated by 6-min unloaded cycling. Using time-resolved near-infrared spectroscopy, absolute concentrations of deoxy- and total[Hb + Mb] were assessed simultaneously in VLs and VLd. PHE raised the V̇O₂ baseline and attenuated the slow component (V̇O2SC) during subsequent exercise. In both muscle regions, PHE reduced the deoxy[Hb + Mb] baseline and increased the amplitude, such that end-exercise deoxy[Hb + Mb] did not differ between muscle regions. Changes in the baseline and amplitude of deoxy[Hb + Mb] induced by PHE were significantly smaller in VLd versus VLs. The primary component time constant of the deoxy[Hb + Mb] kinetics in VLd was greater than that for VLs. The end-exercise total[Hb + Mb] in VLd was lower than that in VLs in both bouts. Despite site-dependent differences in PHE-induced deoxy[Hb + Mb] alterations, neither these changes nor total[Hb + Mb] correlated with V̇O2SC reduction in VLs or VLd. In conclusion, these findings suggest that PHE has less effect on microvascular Q̇O₂-to-V̇O₂ matching during heavy exercise in VLd versus VLs. Moreover, PHE-induced changes in microvascular oxygen transport were unrelated to the PHE-induced speeding of pulmonary V̇O₂ kinetics.