Cardiovascular and neurohormonal responses to lower body negative pressure (LBNP): effect of training and 3 day bed rest.
Both intensive training and bed confinement impair orthostatic tolerance, however, moderate training may exert beneficial effect on cardiovascular adjustment to gravitational stimuli. It was hypothesized that moderate training attenuates effects of bed rest. To test this assumption 24 healthy male volunteers aged 20.8+/-0.9 yrs were subjected to 6 degrees head down bed rest (HDBR) for 3 days before and after 6 weeks of moderate endurance training. Before and after HDBR graded LBNP tests (-15, -30, -50 mmHg) were performed. During these tests heart rate (HR), stroke volume (SV), blood pressure (BP), plasma catecholamines, ACTH, adrenomedullin, atrial natriuretic peptide, plasma renin activity (PRA) and hematocrit were determined. HDBR did not systematically influence LBNP tolerance up to -50 mmHg, but it enhanced rates of reduction of SV, cardiac output and systolic BP and increased elevations of HR and PRA. Training did not alter significantly effects of HDBR on LBNP-induced changes in HR, SV, CO and TPR but it attenuated decrease in systolic BP and diminished increases in plasma noradrenaline and PRA. In conclusion, training has negligible effect on the HDBR-induced changes in central hemodynamics during LBNP but may increase vascular sensitivity to some vasoconstricting factors.
Gasiorowska
A
A
Department of Applied Physiology, Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
Mikulski
T
T
Smorawiński
J
J
Kaciuba-Uściłko
H
H
Cybulski
G
G
Ziemba
A W
AW
Krzemiński
K
K
Niewiadomski
W
W
Nazar
K
K
D000324:Adrenocorticotropic Hormone / Q000097:blood; D053607:Adrenomedullin / Q000097:blood; D000328:Adult; D009320:Atrial Natriuretic Factor / Q000097:blood; D001510:Bed Rest; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D018475:Head-Down Tilt; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012083:Renin / Q000097:blood; D013318:Stroke Volume / Q000502:physiology
D053607:Adrenomedullin; D009320:Atrial Natriuretic Factor; D000324:Adrenocorticotropic Hormone; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine