Maughan Ron J, Watson Phil, Shirreffs Susan M
School of Sport and Exercise Sciences, Loughborough University, Leicestershire, UK.
Sports Med. 2007;37(4-5):396-9. doi: 10.2165/00007256-200737040-00032.
The marathon poses a considerable physical challenge for athletes of all levels. When combined with high heat and humidity, not only is performance potentially compromised, but health and well-being are also at risk. There are well recognised effects of heat and hydration status on the cardiovascular and thermoregulatory systems that can account for the decreased performance and increased sensation of effort that are experienced when competing in the heat. Elevated exercise heart rate and core temperature at the same absolute exercise intensity are commonly reported. Dehydration occurring during exercise in the heat and results in reductions in stroke volume, cardiac output and blood pressure, as well as a marked decline in blood flow to the working muscles. Recent work suggests that hyperthermia may have a direct affect on the CNS and the brain may contribute to fatigue during prolonged exercise in a warm environment. At present, evidence supports a significant role of catecholaminergic neurotransmission, but there are a number of metabolic and circulatory perturbations occurring within the brain that may also be important in the fatigue process.
马拉松对各级运动员来说都是一项巨大的体能挑战。当与高温和高湿度相结合时，不仅运动表现可能会受到影响，健康和福祉也会面临风险。高温和水合状态对心血管和体温调节系统有公认的影响，这可以解释在高温环境下比赛时运动表现下降和用力感增加的现象。通常会报告在相同绝对运动强度下运动心率和核心体温升高。在高温环境下运动时发生的脱水会导致每搏输出量、心输出量和血压降低，以及流向工作肌肉的血流量显著下降。最近的研究表明，体温过高可能对中枢神经系统有直接影响，并且在温暖环境中长时间运动期间大脑可能导致疲劳。目前，有证据支持儿茶酚胺能神经传递起重要作用，但大脑内发生的一些代谢和循环紊乱在疲劳过程中可能也很重要。
