Short-term exercise-heat acclimation enhances skin vasodilation but not hyperthermic hyperpnea in humans exercising in a hot environment

• Published in: European journal of applied physiology Vol. 112; no. 1; pp. 295 - 307
• Main Authors: Fujii, Naoto, Honda, Yasushi, Ogawa, Takeshi, Tsuji, Bun, Kondo, Narihiko, Koga, Shunsaku, Nishiyasu, Takeshi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.01.2012; Springer; Springer Nature B.V
• Subjects: Acclimatization; Adult; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Blood Flow Velocity; Blood pressure; Body Temperature Regulation; Ecosystem; Exercise; Fever; Fever - complications; Fever - physiopathology; Fitness training programs; Fundamental and applied biological sciences. Psychology; Heart rate; Heat; Hot Temperature; Human Physiology; Humans; Hyperthermia; Hyperventilation; Hyperventilation - complications; Hyperventilation - physiopathology; Hypotheses; Male; Occupational Medicine/Industrial Medicine; Original Article; Skin - blood supply; Skin Physiological Phenomena; Sports Medicine; Vasodilation; Ventilation; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Japan; Thermoregulation; Respiration; Body temperature; Adaptation to heat; Short term; Physical exercise; Human; Environmental factor; Vasodilation; Vasomotricity; Heat; Skin; Hyperpnea; Hyperthermia; Adaptation
• ISSN: 1439-6319; 1439-6327; 1439-6327
• DOI: 10.1007/s00421-011-1980-6

We tested the hypothesis that short-term exercise-heat acclimation (EHA) attenuates hyperthermia-induced hyperventilation in humans exercising in a hot environment. Twenty-one male subjects were divided into the two groups: control (C, n  = 11) and EHA ( n  = 10). Subjects in C performed exercise-heat tests [cycle exercise for ~75 min at 58% (37°C, 50% relative humidity)] before and after a 6-day interval with no training, while subjects in EHA performed the tests before and after exercise training in a hot environment (37°C). The training entailed four 20-min bouts of exercise at 50% separated by 10 min of rest daily for 6 days. In C, comparison of the variables recorded before and after the no-training period revealed no changes. In EHA, the training increased resting plasma volume, while it reduced esophageal temperature ( T es ), heart rate at rest and during exercise, and arterial blood pressure and oxygen uptake ( ) during exercise. The training lowered the T es threshold for increasing forearm vascular conductance (FVC), while it increased the slope relating FVC to T es and the peak FVC during exercise. It also lowered minute ventilation ( ) during exercise, but this effect disappeared after removing the influence of on . The training did not change the slope relating ventilatory variables to T es . We conclude that short-term EHA lowers ventilation largely by reducing metabolism, but it does not affect the sensitivity of hyperthermia-induced hyperventilation during submaximal, moderate-intensity exercise in humans.