As the US National Aeronautics and Space Administration (NASA) designs a fitness program for astronauts whose goal is to combat space's toll on the body, their discoveries could help keep us Earthlings in shape.

It might look cool in the movies, but the absence of gravity contributes to muscle weakening, bone loss and decreased cardiovascular conditioning over time.

A team from NASA's Human Research Program Integrated Resistance and Aerobic Training (iRAT) study concludes that high intensity interval training (HIIT) combined with weightlifting and a balanced diet is best for combatting these conditions.

"The theory was that a more stringent regimen of resistance training and interval aerobic exercise would help the astronauts stay fit while on the space station," says principal investigator Dr. Lori Ploutz-Snyder. "This is of particular importance to future crews who travel to Mars."

Here on Earth, the study has implications for those who are bedridden in addition to the healthy.

Conducted on the ground, the study required participants to keep their heads tilted six degrees downwards for 70 days in order to stimulate the shift in bodily fluids that takes place during spaceflight.

"The cool thing about iRAT is that it is the same exercise prescription in the ground study as it is in flight," says Ploutz-Snyder. "We can make comparisons which help validate the bed rest study as an analog for testing fitness. You can get more subjects faster, control more things, and perform more measurements."

Participants were randomized into three groups, one which did not exercise, another that exercised daily and a third group of men was prescribed daily testosterone treatment in addition to exercise.

Diet for all participants was made up of 55 percent carbohydrates, 30 percent fat and 15 percent protein.

The two exercising groups engaged in weight training three days per week and aerobics six days per week.

Aerobic workouts alternated between HIIT and conventional aerobics every other day and all aerobic workouts demanded between 70 to 100 percent of participants' maximum effort.

The study, whose findings imply that faster is better than farther, was published in the journal Medicine & Science in Sports & Exercise.