Diastolic time during recovery from upright exercise in persons without heart disease

To assess the relation between heart rate and diastolic time (cardiac cycle minus electromechanical systole) during the recovery period from upright exercise, 12 normal volunteers were studied immediately after and 2 and 5 minutes after exercise in the upright position. Although heart rate was significantly lower at 5 minutes compared with 2 minutes after exercise (106 vs 116 beats/min), there was significant shortening of diastolic time (from 251 to 230 ms) and total diastole per minute (from 28,634 to 24,220 ms/min). The explanation of this phenomenon appears to be disproportionate lengthening of diastolic time at 2 minutes after exercise, which must represent physiologic response due to increased left ventricular filling as well as continuing adrenergic effects, which would be diminished at 5 minutes. This lengthening of diastolic time also would maintain decreased subendocardial blood flow caused by increased end-diastolic volume.