Vernikos J, Ludwig D A, Ertl A C, Wade C E, Keil L, O'Hara D
Life Science Division, NASA Ames Research Center, Moffett Field, CA, USA.
Aviat Space Environ Med. 1996 Nov;67(11):1069-79.
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 degrees HDBR were used.
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).
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 degrees). 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.
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 an important moderating factor.
背景/假设：为模拟微重力暴露并确定间歇性暴露于被动和主动 +1 Gz 力（从头到脚）在预防头低位卧床休息（HDBR）失健方面的有效性，采用了 4 天 6 度的 HDBR。
志愿者为 9 名年龄在 30 - 50 岁的男性，他们以 15 分钟的时段、每小时一个时段进行 2 小时或 4 小时/天的定期站立或受控行走，或保持连续的 HDBR 对照状态（0 Gz）。
站立 4 小时（S4）完全预防了 HDBR 后体位性耐力的下降，站立 2 小时（S2）部分预防了这种下降（60 度直立倾斜 30 分钟时的存活率）。与 0 Gz 相比，行走 2 小时（W2）和 4 小时（W4）以及 S4 减轻了峰值摄氧量的下降。与 0 Gz 相比，S4 和 W4 均减轻了 HDBR 期间血浆量的损失。随着 HDBR 时间的推移，尿钙排泄增加；然而，W2 和 W4 减弱了尿钙的二次趋势。
我们得出结论，各种生理系统从被动 +1 Gz 或 +1 Gz 活动中受益程度不同，并且除了刺激的持续时间外，姿势刺激的暴露次数可能是一个重要的调节因素。
