TY - JOUR
T1 - Effect of standing or walking on physiological changes induced by head down bed rest
T2 - Implications for spaceflight
AU - Vernikos, J.
AU - Ludwig, D. A.
AU - Ertl, A. C.
AU - Wade, C. E.
AU - Keil, L.
AU - O'Hara, D.
PY - 1996/11/1
Y1 - 1996/11/1
N2 - Background/Hypothesis: To simulate exposure to microgravity and to determine the effectiveness of intermittent exposure to passive and active +1 Gz force (head-to-foot) in preventing head-down bed rest (HDBR) deconditioning, 4 d of 6° HDBR were used. Methods: Volunteers were 9 males, 30-50 yr, who performed periodic standing or controlled walking for 2 or 4 h · d-1 in 15-min bouts, one bout per hour, or remained in a continuous HDBR control condition (0 Gz). Results: Standing 4 h (S4) completely prevented, and standing 2 h (S2) partially prevented, decreases in post-HDBR orthostatic tolerance (survival rates with 30 min of upright tilt at 60°). Walking, both 2 h (W2) and 4 h (W4), and S4 attenuated decreases in peak oxygen uptake compared to 0 Gz. Compared to 0 Gz, both S4 and W4 attenuated plasma volume loss during HDBR. Urinary Ca2+ excretion increased over time with HDBR; the quadratic trend for urinary Ca2+, however, was attenuated with W2 and W4. Conclusions: We concluded that various physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz and, in addition to the duration of the stimulus, the number of exposures to postural stimuli may be important moderating factor.
AB - Background/Hypothesis: To simulate exposure to microgravity and to determine the effectiveness of intermittent exposure to passive and active +1 Gz force (head-to-foot) in preventing head-down bed rest (HDBR) deconditioning, 4 d of 6° HDBR were used. Methods: Volunteers were 9 males, 30-50 yr, who performed periodic standing or controlled walking for 2 or 4 h · d-1 in 15-min bouts, one bout per hour, or remained in a continuous HDBR control condition (0 Gz). Results: Standing 4 h (S4) completely prevented, and standing 2 h (S2) partially prevented, decreases in post-HDBR orthostatic tolerance (survival rates with 30 min of upright tilt at 60°). Walking, both 2 h (W2) and 4 h (W4), and S4 attenuated decreases in peak oxygen uptake compared to 0 Gz. Compared to 0 Gz, both S4 and W4 attenuated plasma volume loss during HDBR. Urinary Ca2+ excretion increased over time with HDBR; the quadratic trend for urinary Ca2+, however, was attenuated with W2 and W4. Conclusions: We concluded that various physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz and, in addition to the duration of the stimulus, the number of exposures to postural stimuli may be important moderating factor.
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M3 - Article
C2 - 8908346
AN - SCOPUS:0029851037
VL - 67
SP - 1069
EP - 1079
JO - Aerospace medicine and human performance
JF - Aerospace medicine and human performance
SN - 2375-6314
IS - 11
ER -