Motivation. The pattern of skeletal muscle deoxygenated hemoglobin and myoglobin (deoxy [Hb + Mb]) during incremental exercise is typically fitted by a sigmoid model and is a proxy of microvascular fractional O2 extraction. Given previous studies showing that metabolic syndrome subjects (MetS) have an altered vascular function, which possibly contributes to an imbalance between O2 supply and O2 demand during exercise, we tested the hypothesis that their sigmoidal increase in deoxy [Hb + Mb] would show a leftward shift when compared to healthy (H) controls, and that the deoxygenation pattern would be associated with cardiorespiratory fitness. Methods. Twenty subjects with MetS (4 women) and 14 H controls (7 women) were recruited. All subjects were submitted to a maximal cardiopulmonary exercise test performed on a cycle ergometer. In addition, a subgroup of twelve subjects with MetS (3 women) and nine H controls (6 women) were submitted to dual energy X-ray absorptiometry (DEXA). Cardiorespiratory fitness was evaluated by the oxygen consumption at the ventilatory threshold (VO2VT) and the peak pulmonary oxygen consumption (VO2peak), which were measured by a metabolic analyzer. Deoxy [Hb + Mb] was measured by near-infrared spectroscopy in the Vastus Lateralis muscle. This signal was normalized to the total response amplitude and expressed in relation to power output (PO) by a sigmoid function {f(x)=f0+A/[1+e-(-c+dx)]}, which generated the variable c/d (PO at 50% of deoxy [Hb + Mb] response). Results. There was no difference between groups’ age (MetS: 37±7 vs. H: 33±9 years, mean±SD, p=0.15), test duration (MetS: 535±90 vs. H: 540±101 s, p=0.88), and absolute VO2peak (MetS: 2.2±0.6 vs. H: 1.9±0.5 L/min, p=0.24). Within the subgroup, there was no difference in VO2peak corrected for lean body mass (MetS: 38.3±5.7 vs. H: 42.2±5.6 ml/kg/min, p=0.13). The deoxygenation pattern was adequately fitted by the sigmoid model (r≥0.95 for all cases). There was no difference for c/d between groups (MetS: 109±25 vs. H: 110±32 W, p=0.88), however there was a significant correlation between c/d and absolute VO2VT and absolute VO2peak in the whole sample (VO2VT r=0.67, p<0.0001; VO2peak r=0.69, p<0.0001), and within groups [(MetS VO2VT r=0.68, p=0.001; VO2peak r=0.69, p=0.001) (H VO2VT r=0.74, p=0.002; VO2peak r=0.76, p=0.001)]. Moreover, within the subgroup submitted to DEXA, we observed a significant correlation between c/d and VO2peak corrected for lean body mass r=0.56, p=0.008 in the whole group, and within groups (MetS: r=0.52, p=0.08; H: r=0.67, p=0.049). Conclusions. The pattern of skeletal muscle deoxygenation was similar between groups, probably due to similar cardiorespiratory fitness, as the deoxygenation pattern was significantly associated with cardiorespiratory fitness.