The first heart sound amplitude has a breaking point and positive relationships with blood lactate concentration and double product in graded exercise
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Continuous recording of heart sounds during graded exercise suggested that there might be a breaking point of heart sounds amplitude (HSBP; Heart Sounds Breaking Point) and that HSBP might have a possibility of an index of anaerobic threshold as a noninvasive method. The purpose of this study is to examine the relationship among amplitude of the first heart sound (HS-1), blood lactate concentration (LA), and double product (DP) during graded exercise. Nine physically active subjects (6 males and 3 females) volunteered to participate in the present study. Each subject performed a 7-to 10-step graded exercise consisting of 3-min of exercise with 1-min of rest between steps on a cycle ergometer at 60 rpm. The intensity of exercise was started at 10 watts and was increased 20 watts for male subjects or 15 watts for female subjects. Phonocardiogram was recorded with a microphone placed on the 4th intercostal space, 5 cm left of the sternum with ECG. The electric signals were sent to a personal computer through an A/D converter. The 10 higher amplitudes of HS-1 were determined from the last 30-sec recording at each step of graded exercise. LA and blood pressure was determined in same 3-min exercise session. Blood pressure during exercise was determined by auscultatory recording method. As results of this study, there were significant positive relationships among amplitude of HS-1, LA, and DP, and also there were significant positive relationships among three work rates at HSBP, lactate threshold, and DP breaking point. These results indicated that HSBP might be an index of anaerobic threshold as a noninvasive method.
- Advances in exercise and sports physiology
Advances in exercise and sports physiology 11(1), 33-39, 2005-04
Japan Society of Exercise and Sports Physiology