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KMID : 0358619960300010043
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Korean Journal of Physiology
1996 Volume.30 No. 1 p.43 ~ p.51
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Spectral Analysis of Heart Rate Variability during Treadmill Exercise at Various Speeds and Grades
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Kim Hyeong-Jin
Kim Ki-Hong
Ahn Dong-Kuk
Park Jae-Sik
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Abstract
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This study was aimed to elucidate the changes in heart rate variability during treadmill exercise at various speeds and grades by spectral analysis. Thirty-three untrained male college students aged were employed to exercise on a treadmill using 4 speeds (4.02, 5.47, 6.76 and 8.05 km/h) and 6 grades (0, 4, 8, 12, 16 and 20%). A fixed speed was selected for each session with the grade increased every 3 min. The electrocardiogram, respiration and the stepping activity were continuously recorded through an A/D converter system on the computer disk. Power spectra of heart rate variability (RRV) were obtained by use of a fast Fourier transform algorithm. The frequency domain was divided into 3 bands: Heart rate was at rest and showed a steady increase during treadmill exercise with increasing speed and grade up to Total power of HRV was at rest and progressively decreased during exercise down to The %VLF power of HRV was at rest and showed no significant change during exercise except for a decrease observed at the highest intensity of exercise. The %LF power was at rest and showed a progressive decrease down to during those stages of exercise where heart rate was over 135 beats/min. The %HF power was at rest and showed a progressive increase up to during higher intensity exercise where heart rate was over 165 beats/min. Peak frequency of HF band was at rest and was shifted to higher frequencies up to at heart rates greater than 135 beats/min. Respiratory frequency was breaths/min at rest and significantly increased during exercise up to breaths/min. Stride frequency during treadmill exercise showed an increasing tendency with increasing speed from steps/min at 4.02 km/h to at 8.05 km/h. It was concluded that total power of HRV decreased progressively with increasing exercise intensity due to the withdrawal of parasympathetic activity. At higher exercise intensity, % LF power decreased and %HF power increased with its peak frequency shifted to higher values in a progressive mode with increasing speed and grade, reflecting a readjustment in the cardiovascular system and the increased respiration and its rate, respectively.
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KEYWORD
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Fourier transform, Parasympathetic activity, Power spectrum, Stride frequency
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