The First Heart Sound Immediately after Exercise as an Index of Exercise Stress

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INTRODUCTION. This study investigated whether the amplitude of the first heart sound (AHS-1) and the diastolic time (DT) recorded immediately after exercising could be related to those values during exercise.METHODS. Nine male volunteers (24.6±2.9 years old) participated in this study. A discontinuous graded exercise test was performed on an electrically braked cycle ergometer. The external phonocardiograms were recorded during the test. The 10 highest AHS-1 during the last 30 sec at each stages and 10 consecutive AHS-1 immediately after each stage of exertion were measured. The DT was calculated as the systolic time subtracted from the cardiac cycle time interval assessed by the waveform of the heart sounds in the same time range as the above analysis.RESULTS. The change of AHS-1 during exercise and immediately after exercise at each stage demonstrated a significant correlation (r=0.979, p<0.01). The workloads at the breaking point during and immediately after exercise were the same. There were significant correlations between the DT during exercise and immediately after exercise in all (r=0.951 to 0.993, p<0.01).CONCLUSION. The results of this study clarified that AHS-1 and DT during exercise can be estimated from the phonocardiogram that is recorded immediately after exercise.