The pressure of returning to earth

OT/PT project may help astronauts avoid the negative aftereffects of lengthy space flights

By Greg Scheiderer

When astronauts spend a long time in space, they often have dizziness or fainting spells for a couple of weeks after returning to Mother Earth. Research under way at the university may help minimize the phenomenon.

The reason for the symptoms is orthostatic intolerance. Simply put, in space an astro-naut’s cardiovascular system does not have to work against gravity, and so the blood vessels lose their ability to push against the weight of blood. Return to gravity and the system has a tough time keeping the blood flowing to the brain.

The question, then, is how can orthostatic intolerance be reduced? Past research has focused on upright exercises such as running, but perhaps other forms of conditioning could be more beneficial. Senior exercise science major Jess Sotelo decided to compare female endurance runners and rowers and find out if their systems respond differently when exposed to orthostatic stress.

The exercise science department does not have adequate budget to launch subjects into space, but Sotelo’s work is possible anyway, thanks to a contraption called a lower-body negative pressure chamber. It’s basically a big vacuum tube, a cylinder large enough to enclose a person’s lower body. It has a flexible cover that can be cinched around the subject’s waist for an airtight seal. Then subjects are exposed to orthostatic stress–air is sucked out of the chamber, decreasing pressure around the lower body and making it more difficult for blood to be pumped. The subject’s heart rate and other vital signs are monitored and recorded as a measure of how her system reacts to this stress.

Tom Wells, assistant professor of exercise science, who is supervising Sotelo’s work, says it’s not quite like sending someone to space, but the chamber makes a significant difference in pressure.

"It is like their torso is here at sea level and their lower body is in Denver," said Wells. "That’s enough to create measurable differences in the cardiovascular system."

Sotelo’s study is called "Cardiovascular Responses to Lower Body Negative Pressure in Highly Trained Female Rowers and Runners."

"The subjects must be national-caliber athletes," said Sotelo, "and they can’t do any cross training."

If it is found that elite athletes who stick to one particular conditioning regimen have better orthostatic tolerance, astronauts may benefit from a similar exercise program.

A grant from the Washington Space Consortium, established by NASA, supports Sotelo’s research. The grant covers equipment and also funds a space science unit in the exercise physiology course. It also paid for another student to continue Sotelo’s research this past summer, this time examining weight training and orthostatic tolerance.

Sotelo became interested in space in part because her mother, a teacher in Alaska, teaches on the subject. She plans to go to medical school, possibly with the support of the Air Force, and would like to work in the field of aerospace medicine or even participate in space flight.

In addition to her research project and course work, Sotelo, who is minoring in biology, also is a runner. She has been captain of the Puget Sound track team for the past two years.