An Analysis of Heart Rateesponse to Exercise

Abstract

Heart rate response to exercise and recovery after exercise were studied analytically on the basis that any energy extracted from a muscle must ultimately be supplied by oxidation. Any discrepancy between oxygen supply rate and equivalent oxygen consumption rate was assumed to be made up by utilizing a finite reserve; thus allowing supply to lag consumption at the onset of exercise. Heart rate was assumed and experimentally demonstrated to be linearly related to oxygen supply rate during both steady-state and the transition period after exercise starts or stops. During recovery the withdrawals from reserves are repaid as heart rate returns to normal. Consideration of these factors resulted in an exponential heart rate response equation which closely agreed with observations. Coefficients, evaluated from experimental data, gave average time constants of 1.2 to 1.7 sec. with recovery being slower than response to exercise. Integration of this equation over the exercise range gave an estimate of the deficiency of supply as compared to consumption. A similar integration over the recovery phase indicated that in this range, supply exceeded consumption by at least as much as it was deficient during the exercise phase.