title: Is peak quadriceps blood flow in humans even higher during exercise with hypoxemia?
abstract: Blood flow (Q) to quadriceps muscles was measured by thermal dilution in six men during rest and dynamic exercise [20, 38, and 42.5-60 W (peak load)] restricted to quadriceps of one leg in normoxia (N) and hypoxemia (H; 10-11% O2). Without exception Q and quadriceps vascular conductance were higher in H. Arterial mean pressure, lactate, norepinephrine, and epinephrine all rose when work exceeded 20 W. Q in N was 0.25, 3.28, 4.27, and 5.81 l/min (rest to peak exercise) and in H was 0.25, 4.08, 5.24, and 6.58 l/min. Peak Q per 100 grams of muscle (quadriceps mass = 2.2 kg) was 273.3 (N) and 308.8 ml/min (H). Quadriceps VO2 (Q X femoral A-VO2 difference) was 25, 388, 556, and 771 ml/min (N) and 25, 390, 556, and 743 (lower peak load in H)-net mechanical efficiency was 23%. Muscle O2 delivery (Q X arterial O2 content) was unaffected by H; O2 extraction fell in H but femoral venous O2 content remained near 6 (N) and 5 ml/100 ml (H) at all workloads, in contrast to much lower values in whole body exercise. In H muscle Q can rise to even higher peak values, without apparent limit, when the mass of active muscle is too small to overwhelm the pumping capacity of the heart.
mesh_terms: D000328:Adult; D001794:Blood Pressure; D005263:Femoral Artery / Q000503:physiopathology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D009132:Muscles / Q000098:blood supply* / Q000378:metabolism; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D005082:Physical Exertion; D012039:Regional Blood Flow; D013848:Thigh
chemical_list: D010100:Oxygen