The effect of increased body temperature due to exercise on the heart rate and on the maximal aerobic power

The effect of an increased body temperature (T r) elicited by prolonged heavy exercise at normal ambient temperature in absence of any heat stress, on the maximal aerobic power ( [(V)\dot]O2 maxVO2max) and on heart rate (HR) has been studied. The prolonged exercise consisted in running for 1 hr on a motor driven treadmill, this leading to an average increase of T r of 1.2° C. Oxygen consumption ( [(V)\dot]O2 VO2), ventilation (V I ), HR and T r were measured at rest and every 10 min during the prolonged exercise. Before and after this exercise indirect measurement of [(V)\dot]O2 maxVO2maxwere made. After the exercise, HR in submaximal exercise was increased, the increase being less pronounced the heavier the exercise. The HR increment was 17.5 beats/min per 1° C rise in T r in the exercise involving an oxygen comsumption of 22 ml/kg·min and it dropped to 7.5 b/min · °C when the O2 consumption increased to 32.4 ml/kg · · min. [(V)\dot]O2 maxVO2maxas calculated indirectly from HR values in submaximal exercise remained essentially the same before and after the treadmill run.