Effect of Head-Down Bed Rest on the Neuroendocrine Response
to Orthostatic Stress in Physically Fit Men
J. KOŠKA, L. KŠINANTOVÁ, R.
KVETŇANSKÝ, M. MARKO1, D. HAMAR2, M.
VIGAŠ, R. HATALA3
Institute of Experimental Endocrinology, Slovak Academy of
Sciences, 1Hospital of Ministry of Defense
Slovak Republic, 2Faculty of Physical Education
and Sports, Comenius University, 3Slovak
Cardiovascular Institute, Bratislava, Slovak Republic
Received April 5, 2002
Accepted June 24, 2002
The role of neuroendocrine responsiveness in the development of
orthostatic intolerance after bed rest was studied in physically
fit subjects. Head-down bed-rest (HDBR, –6 degrees, 4 days) was
performed in 15 men after 6 weeks of aerobic training. The
standing test was performed before, after training and on day 4
of the HDBR. Orthostatic intolerance was observed in one subject
before and after training. The blood pressure response after
training was enhanced (mean BP increments 18±2 vs. 13±2 mm Hg,
p<0.05, means ± S.E.M.), although noradrenaline response was
diminished (1.38±0.18 vs. 2.76±0.25 mol.l-1, p<0.01).
Orthostatic intolerance after HDBR was observed in 10 subjects,
the BP response was blunted, and noradrenaline as well as plasma
renin activity (PRA) responses were augmented (NA 3.10±0.33
mol.l-1, p<0.001; PRA 2.98±1.12 vs. 0.85±0.15 ng.ml-1, p<0.05).
Plasma noradrenaline, adrenaline and aldosterone responses in
orthostatic intolerant subjects were similar to the tolerant
group. We conclude that six weeks of training attenuated the
sympathetic response to standing and had no effect on the
orthostatic tolerance. In orthostatic intolerance the BP
response induced by subsequent HDBR was absent despite an
enhanced sympathetic response.
Standing • Noradrenaline • Adrenaline • Plasma renin activity •
Juraj Koška, M.D., PhD., Institute of Experimental
Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06
Bratislava, Slovakia, fax: +421 2 5477 4247, e-mail: