Chou Ting-Heng, Coyle Edward F
Center for Regenerative Medicine, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA.
Department of Kinesiology and Health Education, The University of Texas at Austin, Texas, Tx, USA.
Temperature (Austin). 2022 Aug 17;10(3):326-357. doi: 10.1080/23328940.2022.2109931. eCollection 2023.
Integrative cardiovascular responses to heat stress during endurance exercise depend on various variables, such as thermal stress and exercise intensity. This review addresses how increases in skin temperature alter and challenge the integrative cardiovascular system during upright submaximal endurance exercise, especially when skin is hot (i.e. >38°C). Current evidence suggests that exercise intensity plays a significant role in cardiovascular responses to hot skin during exercise. At rest and during mild intensity exercise, hot skin increases skin blood flow and abolishes cutaneous venous tone, which causes blood pooling in the skin while having little impact on stroke volume and thus cardiac output is increased with an increase in heart rate. When the heart rate is at relatively low levels, small increases in heart rate, skin blood flow, and cutaneous venous volume do not compromise stroke volume, so cardiac output can increase to fulfill the demands for maintaining blood pressure, heat dissipation, and the exercising muscle. On the contrary, during more intense exercise, hot skin does not abolish exercise-induced cutaneous venoconstriction possibly due to high sympathetic nerve activities; thus, it does not cause blood pooling in the skin. However, hot skin reduces stroke volume, which is associated with a decrease in ventricular filling time caused by an increase in heart rate. When the heart rate is high during moderate or intense exercise, even a slight reduction in ventricular filling time lowers stroke volume. Cardiac output is therefore not elevated when skin is hot during moderate intensity exercise.
耐力运动期间对热应激的综合心血管反应取决于多种变量，如热应激和运动强度。本综述探讨了在直立次最大耐力运动期间，尤其是皮肤温度较高（即>38°C）时，皮肤温度升高如何改变并挑战综合心血管系统。目前的证据表明，运动强度在运动期间对热皮肤的心血管反应中起着重要作用。在休息和轻度强度运动期间，热皮肤会增加皮肤血流量并消除皮肤静脉张力，这会导致血液在皮肤中淤积，而对每搏输出量影响很小，因此心输出量会随着心率的增加而增加。当心率处于相对较低水平时，心率、皮肤血流量和皮肤静脉容量的小幅增加不会损害每搏输出量，因此心输出量可以增加以满足维持血压、散热和运动肌肉的需求。相反，在更剧烈的运动期间，热皮肤可能由于高交感神经活动而不会消除运动引起的皮肤血管收缩；因此，它不会导致血液在皮肤中淤积。然而，热皮肤会降低每搏输出量，这与心率增加导致心室充盈时间减少有关。当中等强度或剧烈运动期间心率较高时，即使心室充盈时间稍有减少也会降低每搏输出量。因此，在中等强度运动期间皮肤热时，心输出量不会升高。
