The vigorous exercise, which they began aboard Mir, is intended to bolster their cardiovascular conditioning. Once they boarded the shuttle, the three men also began a daily practice of placing their lower torsos in a sleeping bag-like device that forms an airtight seal at the waist. A partial vacuum that is gradually created in the bags pulls back into their lower extremities bodily fluids that pool in their chests and faces while they are weightless. The technique, pioneered aboard America's Skylab space station in the early 1970s, should help to protect them from fainting when they attempt to stand for the first time on Earth. The three will join the shuttle's five other occupants in drinking more than a quart of salted water before their atmospheric re-entry early Friday.
Water loss is another phenomenon of spaceflight, and the briny solution helps prevent dehydration.
Thagard, Dezhurov and Strekalov will don bulky pressure suits for the plunge toward Earth and recline in special seats installed aboard the shuttle. Those are the last of the major countermeasures developed to keep the first forces of gravity from causing them to black out as the shuttle rolls to a stop on the runway. It is inside that vehicle, which is off limits to cameras, that Thagard will likely make his first attempt to stand. Doctors and other medics will be on hand to assist those who require help.