Sixty days in bed for science

(NC)-At first glace, bedridden patients don’t seem to have much in common with astronauts. After all, astronauts are among the fittest people on earth. But when they go into space, especially for long periods of time, their bodies react to microgravity in ways that weaken their bones, muscles and hearts-effects remarkably similar to those experienced by people confined to bed.

An international study starting in January will examine these effects and methods to counteract them. The findings may improve the rehabilitation of bedridden patients and astronauts returning from long spaceflights, such as a trip to Mars.

The study, based in France, involves 24 women who’ll remain in bed for 60 days. Eight will do exercises, eight will receive nutritional supplements and eight will be the control group. This is the first large-scale international bedrest study using females.

The project is sponsored by several space agencies, including the Canadian Space Agency (CSA). The CSA and the Canadian Institute of Health Research are funding experiments by two Canadian teams led by Dr. Guy Trudel of the University of Ottawa and Dr. Richard Hughson of the University of Waterloo.&l;/>

Trudel, whose work involves rehabilitating people immobilized for long periods by illness or injury, said that in addition to bone and muscle weakness, these patients often suffer from anemia – a decrease in red blood cells that causes fatigue. The cause is unknown and Trudel will use the bedrest study to test whether there’s “a specific mechanism of anemia that’s brought about by immobility.”

He’ll also study tendon weakness, which can cause ruptures when bedridden patients start rehabilitation. “We don’t know what level of effort they can put forth safely,” he said. He’ll examine whether techniques like ultrasound and MRI can measure or predict the strength of tendons.

Hughson will focus on cardiovascular effects of bedrest, during which, as in spaceflight, “the heart essentially forgets how to respond to gravity.”

This can cause hypotension, where the heart can’t pump enough blood to the head, causing lightheadedness or fainting when someone stands up. Immobility or microgravity can actually cause a reduction in blood volume, which gives the heart even less blood to pump.

There’s also evidence the heart gets smaller in space or during bedrest, which reduces fitness “because you’re not as efficient at pumping blood out to the muscles when they demand oxygen,” Hughson said.

Eight of the bedrest subjects will use a device that simulates running on a treadmill and another that allows resistance exercises. During rehabilitation following the bedrest period and for at least a year after, their physical fitness and bone and muscle mass will be compared with subjects who didn’t exercise.

Hughson will also study whether bedrest and, by extension, spaceflight accelerate aging by looking at blood markers associated with coronary artery disease-cholesterol build-up that can lead to heart attacks. “If we see an increase in those markers, it’s telling us that physical inactivity is a strong stimulus to these undesirable end points,” he said.

– News Canada