<jats:title>Abstract</jats:title><jats:sec> <jats:title>Purpose</jats:title> <jats:p>We tested the hypothesis that incremental ramp cycling exercise performed in the supine position (<jats:italic>S</jats:italic>) would be associated with an increased reliance on muscle deoxygenation (deoxy[heme]) in the deep and superficial <jats:italic>vastus lateralis</jats:italic> (VLd and VLs, respectively) and the superficial <jats:italic>rectus femoris</jats:italic> (RFs) when compared to the upright position (<jats:italic>U</jats:italic>).</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>11 healthy men completed ramp incremental exercise tests in <jats:italic>S</jats:italic> and <jats:italic>U</jats:italic>. Pulmonary <jats:inline-formula><jats:alternatives><jats:tex-math>$$\dot{V}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>V</mml:mi> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2</jats:sub> was measured breath-by-breath; deoxy[heme] was determined via time-resolved near-infrared spectroscopy in the VLd, VLs and RFs.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Supine exercise increased the overall change in deoxy[heme] from baseline to maximal exercise in the VLs (<jats:italic>S</jats:italic>: 38 ± 23 vs. <jats:italic>U</jats:italic>: 26 ± 15 μM, <jats:italic>P</jats:italic> < 0.001) and RFs (<jats:italic>S</jats:italic>: 36 ± 21 vs. <jats:italic>U</jats:italic>: 25 ± 15 μM, <jats:italic>P</jats:italic> < 0.001), but not in the VLd (<jats:italic>S</jats:italic>: 32 ± 23 vs. <jats:italic>U</jats:italic>: 29 ± 26 μM, <jats:italic>P</jats:italic> > 0.05).</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The present study supports that the impaired balance between O<jats:sub>2</jats:sub> delivery and O<jats:sub>2</jats:sub> utilization observed during supine exercise is a regional phenomenon within superficial muscles. Thus, deep muscle defended its O<jats:sub>2</jats:sub> delivery/utilization balance against the supine-induced reductions in perfusion pressure. The differential responses of these muscle regions may be explained by a regional heterogeneity of vascular and metabolic control properties, perhaps related to fiber type composition.</jats:p> </jats:sec>