1995 Fiscal Year Final Research Report Summary
Effect of endurance training on autonomic reflexes in humans
| Project/Area Number |
06670092
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Environmental physiology (including Physical medicine and Nutritional physiology)
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| Research Institution | University of Occupational and Environmental Health |
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Principal Investigator |
SAGAWA Sueko Department of Physiology school of Medicine, University of Occupational and Environmental Health, Associate Professor, 医学部, 助教授 (20035489)
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| Project Period (FY) |
1994 – 1995
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| Keywords | baroreflex / LBNP / carotid baroreceptors / R-R interval / neck chamber / athlete |
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| Research Abstract |
There is evidence suggesting that endurance-trained athletes (ET) fail to maintain blood pressure responses to gravitational challenges such as head-up tilt, standing, or lower body negative pressure (LBNP). The purpose of the present study was to examine whether gravitational intolerance in ET was due to a blunted carotid baroreceptor-cardiac responsiveness. Twenty ET females (long distance runner, 18.4<plus-minus>2.2y.o) and 9 endurance-untrained female (UT,20.4<plus-minus>0.9y.o.) underwent a 21-min bout of graded LBNP (0 to -60mmHg). Sixty % of ET group showed presyncopal symptoms during LBNP,whereas only 22% of UT became presyncopic. Carotid baroreceptor-cardiac responses were estimated by using a neck chamber. R-R intervals were plotted against carotid distending pressures and the response was analyzed by applying a four-parameter sigmoidal logistic function. The maximal gain of the curve in ET group was greater (P<0.05) than that of UT group, indicating increased baroreflex sensitivity. The centering point of the curve, an indicator of the operating point, was identical. There was a significant correlation between VO_2max and maximal gain (r=0.693, P<0.005). These results may suggest that attenuated baroreflex control of the heart rate in ET is not responsible for the mechanisms of the gravitational intolerance.
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