Sex-related differences in muscle deoxygenation during ramp incremental exercise

•Local O2 extraction was larger in women than in men during ramp incremental exercise.•The HHb signal breaking point was associated with the respiratory compensation point.•Results suggest poorer microvascular perfusion in women than men during ramp tests.

Sex-specific differences in the temporal profiles of fractional O2 extraction during incremental cycling were examined using changes in near-infrared spectroscopy (NIRS)-derived muscle deoxygenated hemoglobin concentration (Δ[HHb]) and breath-by-breath pulmonary O2 uptake (V˙O2p) measurements. Subject's (men: n = 10; women: n = 10) Δ[HHb] data were normalized to 100% of the response, plotted as a function V˙O2p, %V˙O2p, power output (PO), and % PO, and fit with a piecewise double-linear regression model. The slope of the first segment of the double linear model was significantly greater in women compared to men when %Δ[HHb] was plotted as a function of V˙O2p, %V˙O2p and PO (p < 0.05). Both sexes displayed a near-plateau in the %Δ[HHb] which occurred at an exercise intensity near the respiratory compensation point. Thus, young women display a poorer ability to deliver O2 to the exercising tissue compared to men and oxidative demands must be supplemented by a greater fractional O2 extraction.