HEART RATE AND PLASMA CATECHOLAMINES RESPONSES TO EXERCISE AT VARIOUS INTENSITIES

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  • FUJII NOBUHARU
    <I>University of Tsukuba, Doctoral Program in Health and Sport Sciences</I>
  • NABEKURA YOSHIHARU
    <I>University of Tsukuba, Institute of Health and Sport Sciences</I>
  • GWON OSUNG
    <I>University of Tsukuba, Doctoral Program in Health and Sport Sciences</I>
  • YAMAZAKI FUMIO
    <I>University of Tsukuba, Doctoral Program in Health and Sport Sciences</I>
  • HOMMA SACHIKO
    <I>University of Tsukuba, Institute of Health and Sport Sciences</I>
  • IKEGAMI HARUO
    <I>University of Tsukuba, Institute of Health and Sport Sciences</I>

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  • 運動強度の増大に対する心拍数および血漿カテコールアミンの応答
  • ウンドウ キョウド ノ ゾウダイ ニ タイスル シンパクスウ オヨビ ケッショ

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Abstract

To investigate the responses of heart rate and plasma catecholamines to exercise at various intensities, seven healthy adult males performed 6-min bouts of cycling exercise at 30, 50, 70 and 90% of maximal oxygen consumption (VO2max) . Heart rate (HR), plasma noradrenaline (NA), plasma adrenaline (A), blood lactate (La) and coefficient of variation of R-R intervals (CVRR) were determined i n each case.<BR>The following results were obtained:<BR>1) CVRR showed a sharp decline to the extent of 50%VO2max, then fell more slightly for heavier exercise.<BR>2) NA and A significantly increased from resting value at 50%VO2max, and followed by further increase with exercise intensity. NA/A increasd in proportion to exercise intensity.<BR>3) The results of multiple regression analysis of HR (dependent variable) and NA, A and CVRR (independent variables) indicated the greatest standardized partial regression coefficient for CVRR in the case of low intensity exercise, and for NA with high intensity exercise.<BR>4) La increased abruptly at 70%VO2max, whereas NA and A rose drastically at 90%VO2max.<BR>The conclusion based on these results is as follows: HR is mainly influenced by change in parasympathetic tone to the extent of 50%VO2max, whereas sympathetic and adrenomedullary activity are the main factors controlling HR in heavier exercise. Within the submaximal level of exercise, sympathetic activity increases more markedly than that of adrenomedullary activity. Abrupt increase in La may be independent of catecholamines.

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