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 totalHb + 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 deoxyHb + Mb baseline and increased the amplitude, such that end-exercise deoxyHb + Mb did not differ between muscle regions. Changes in the baseline and amplitude of deoxyHb + Mb induced by PHE were significantly smaller in VLd versus VLs. The primary component time constant of the deoxyHb + Mb kinetics in VLd was greater than that for VLs. The end-exercise totalHb + Mb in VLd was lower than that in VLs in both bouts. Despite site-dependent differences in PHE-induced deoxyHb + Mb alterations, neither these changes nor totalHb + 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.