1997 Fiscal Year Final Research Report Summary
Neuro-endocrine responses to lower body negative pressure in exercise-trained subjects
| Project/Area Number |
08670093
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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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 University of Occupational and Environmental Health, , Department of Physiology, School of Medicine, Associate Professor, 医学部・生理学, 助教授 (20035489)
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| Project Period (FY) |
1996 – 1997
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| Keywords | baroreflex / LBNP / norepinephrine / syncopic / exercise training / total peripheral resistance |
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| Research Abstract |
There is an evidence suggesting that exercise-trained subjects (ET) becomes vulnerable to maintain blood pressure during a gravitational challenge such as upright standing or lower body negative pressure (LBNP). The purpose of the present study was to examine whether intolerance to LBNP in ET was attributable to blunted baroreflex responses. Blood pressure, stroke volume (SV) , and heart rate (HR) during graded LBNP (0 to-60 mmHg) were measured in 26 long distance female runners (18.4+/-0.6yr) and 23 age-matched control subjects. Blood samples were taken to measure the plasma level of norepinephrine (NE). Leg compliance was higher (P<0.05) in ET than control subjects. 17 out of 26 ET (65.4%) showed presyncopal symptoms during LBNP,whereas 8 out of 23 (34.8%) control subjects became presyncopic. Subjects who showed presyncopic signs during LBNP had a greater (P<0.05) reduction of SV regardless of the group. The magnitude of increase in HR,total peripheral resistance, and NE during LBNP was greater (P<0.05) in syncopic subjects compared with non-syncopic subjects. There was no training-related change in the regression between NE ans SV.This suggests that the sensitivity of vasoconstriction response during LBNP is not affected by physical training per se. Thus, we conclude that exercise training may induce a greater reduction of SV during LBNP and this reduction may lead to a greater baroreflex response. Increase in leg compliance is one of the contributing factors for greater reduction of SV.
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