Wasting muscles threaten missions to Mars
Astronauts who spend months in space become as physically weak as 80-year-olds, a study has found.
Researchers in the US made the discovery after testing muscle tissue taken from crew members on the International Space Station (ISS).
The calf-biopsy samples revealed that after six months in orbit the physical work capacity of astronauts fell by 40pc.
This was equivalent to the muscles of an astronaut aged 30-50 wasting away to the level of an average 80-year-old.
The deterioration occurred despite crew members taking regular exercise on the space station. The ISS is equipped with two treadmills and an exercise cycle.
Scientists fear the effects of extended weightlessness on skeletal muscle will pose a significant safety risk for future manned Mars missions.
Nasa estimates that it would take a crew 10 months to reach Mars. With a one-year stay, a mission could take as long as three years.
Professor Robert Fitts, from Marquette University in Wisconsin in the US wrote in the 'Journal of Physiology': "The main findings were that prolonged weightlessness produced substantial loss of fibre mass, force, and power.
"An obvious conclusion is that the exercise counter-measures employed were incapable of providing the high-intensity needed to adequately protect fibre and muscle mass, and that the crew's ability to perform strenuous exercise might be seriously compromised.
"Our results highlight the need to study new exercise programmes on the ISS that employ high resistance and contractions over a wide range of motion to mimic the range occurring in Earth's 1G environment."
Prof Fitts believes if astronauts tried to travel to Mars today they would have trouble performing even routine work in a space suit.
The most affected muscles, such as the calf, could weaken by as much as 50pc.
Nine American astronauts and Russian cosmonauts were tested before, and after, spending 180 days on the ISS.
Analysis showed "substantial" losses caused by muscle atrophy.
Starting the space flight in good physical shape did not help, the scientists found. Crew members who began with the biggest muscles also showed the greatest declines.