Cardiovascular strain impairs prolonged self-paced exercise in the heat
Cardiovascular strain impairs prolonged self-paced exercise in the heat
复制标题
DOI：
10.1113/expphysiol.2010.054213
复制
发表时间：
2011-02-01
影响因子：
2.7
通讯作者：
Thompson, Martin W.
中科院分区：
文献类型：
--
作者：
Periard, Julien D.;Cramer, Matthew N.;Thompson, Martin W.
有人提出，在炎热的自我调节的锻炼是由一个预期的减少工作率的基础上的储热率。然而，性能可能会受到损害的发展，体温过高，并伴随心血管紧张增加相对运动强度的上升。本研究旨在探讨热负荷对热环境下自行步速运动时心血管功能和功率输出的影响。8名经过耐力训练的自行车运动员在高温（35摄氏度）和热中性条件（20摄氏度）下进行了40公里的模拟计时赛，同时测量了功率输出、平均动脉压、心率、摄氧量和心输出量。在热条件下，时间试验持续时间为64.3 ± 2.8 min（242.1 W），在热中性条件下为59.8 ± 2.6 min（279.4 W）（P < 0.01）。从20 min开始，热负荷下的功率输出较热中性负荷下的运动功率输出降低（P < 0.05）。直肠温度达到39.8 +/- 0.3（热）和38.9 +/- 0.2 ℃（热中性; P < 0.01）。从10分钟开始，平均皮肤温度与高温时相似，高出7.5 ℃，皮肤血流量显著增加（P < 0.01）。与热中性条件相比，热负荷运动时心率增加约8次/min，而每搏输出量、心输出量和平均动脉压均显著降低（P < 0.05）。在最大努力运动的最后一公里期间测量的峰值摄氧量达到实验前对照值的77%（热）和95%（热中性）（P < 0.01）。我们得出的结论是，在高温下长时间、高强度的自行节奏运动期间，体温调节介导的心血管紧张度升高与可持续功率输出、峰值摄氧量和最大功率输出的减少有关。
It has been proposed that self-paced exercise in the heat is regulated by an anticipatory reduction in work rate based on the rate of heat storage. However, performance may be impaired by the development of hyperthermia and concomitant rise in cardiovascular strain increasing relative exercise intensity. This study evaluated the influence of thermal strain on cardiovascular function and power output during self-paced exercise in the heat. Eight endurance-trained cyclists performed a 40 km simulated time trial in hot (35 degrees C) and thermoneutral conditions (20 degrees C), while power output, mean arterial pressure, heart rate, oxygen uptake and cardiac output were measured. Time trial duration was 64.3 +/- 2.8 min (242.1 W) in the hot condition and 59.8 +/- 2.6 min (279.4 W) in the thermoneutral condition (P < 0.01). Power output in the heat was depressed from 20 min onwards compared with exercise in the thermoneutral condition (P < 0.05). Rectal temperature reached 39.8 +/- 0.3 (hot) and 38.9 +/- 0.2 degrees C (thermoneutral; P < 0.01). From 10 min onwards, mean skin temperature was similar to 7.5 degrees C higher in the heat, and skin blood flow was significantly elevated (P < 0.01). Heart rate was similar to 8 beats min-1 higher throughout hot exercise, while stroke volume, cardiac output and mean arterial pressure were significantly depressed compared with the thermoneutral condition (P < 0.05). Peak oxygen uptake measured during the final kilometre of exercise at maximal effort reached 77 (hot) and 95% (thermoneutral) of pre-experimental control values (P < 0.01). We conclude that a thermoregulatory-mediated rise in cardiovascular strain is associated with reductions in sustainable power output, peak oxygen uptake and maximal power output during prolonged, intense self-paced exercise in the heat.