During maximal whole body exercise VO2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher O2 delivery and leg VO2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution) into the right femoral artery at a rate of 80 microg.kg body mass-1.min-1. During near-maximal exercise (92% of VO2 peak), the infusion of ATP increased leg vascular conductance (+43%, P<0.05), leg blood flow (+20%, 1.7 l/min, P<0.05), and leg O2 delivery (+20%, 0.3 l/min, P<0.05). No effects were observed on leg or systemic VO2. Leg O2 fractional extraction was decreased from 85+/-3 (control) to 78+/-4% (ATP) in the infused leg (P<0.05), while it remained unchanged in the left leg (84+/-2 and 83+/-2%; control and ATP; n=3). ATP infusion at maximal exercise increased leg vascular conductance by 17% (P<0.05), while leg blood flow tended to be elevated by 0.8 l/min (P=0.08). However, neither systemic nor leg peak VO2 values where enhanced due to a reduction of O2 extraction from 84+/-4 to 76+/-4%, in the control and ATP conditions, respectively (P<0.05). In summary, the VO2 of the skeletal muscles of the lower extremities is not enhanced by limb vasodilation at near-maximal or maximal exercise in humans. The fact that ATP infusion resulted in a reduction of O2 extraction across the exercising leg suggests a vasodilating effect of ATP on less-active muscle fibers and other noncontracting tissues and that under normal conditions these regions are under high vasoconstrictor influence to ensure the most efficient flow distribution of the available cardiac output to the most active muscle fibers of the exercising limb.

译文

在最大的全身运动期间,VO2峰值受到O2输送的限制。反过来,尽管在接近最大运动时的血流必须受到交感神经系统的限制,以维持平均动脉压。为了确定在人类接近最大和最大运动期间,增强腿部的血管舒张是否会导致较高的O2递送和腿部VO2,七名男子在自行车测功机上进行了两次最大增量运动测试。以随机顺序,进行一次测试,其中一次 (对照运动) 以80微克kg身体mass-1.min-1的速率将ATP (8 mg在1毫升的等渗盐溶液中) 输注到右股动脉中。在接近最大运动 (VO2峰的92%) 期间,ATP的输注增加了腿部血管电导 (43%,P<0.05),腿部血流量 (20%,1.7 l/min,P<0.05) 和腿部O2的输送 (20%,0.3 l/min,P<0.05)。未观察到对腿部或全身vo2的影响。腿部O2分数提取在输注的腿部从85 +/-3 (对照) 降低到78 +/-4% (ATP) (P & lt; 0.05),而在左腿保持不变 (84 +/-2和83 +/-2%; 对照和ATP; n = 3)。最大运动时ATP输注可增加17% (P<0.05),而腿部血流量可增加0.8 l/min (P = 0.08)。然而,在对照和ATP条件下,由于O2提取从84 +/-4降低到76 +/-4% 而增强的体循环或腿部峰值VO2值都没有增强 (P<0.05)。总而言之,在人类几乎最大或最大的运动中,肢体血管舒张不会增强下肢骨骼肌的VO2。ATP输注导致运动腿部O2提取减少的事实表明,ATP对活动较少的肌纤维和其他非收缩组织具有血管舒张作用,并且在正常条件下,这些区域处于较高的血管收缩作用下,以确保最有效的血流分布。锻炼肢体的肌肉纤维。

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