Spaceflights present a significant risk to muscles of astronauts, revealed new study published in The Journal of Physiology. Scientists have simulated the impact of 21 day spaceflights on the body, and the impact of low gravity environments such as the Moon or Mars.
During spaceflights, and in future habitats on the Moon or Mars, humans are or will be exposed to a condition of "microgravity", in other words to a gravitational field much smaller compared to that present on Earth. This environmental stress has negative consequences on many organs, systems and functions of the body, including bone, muscle, plus the cardiovascular, respiratory and nervous systems. Spaceflights and reduced gravity habitats will expose astronauts also to low oxygen environments. The hypoxic stress will therefore be superimposed upon that related to reduced gravity.
Mitochondria are found in cells and they use oxygen to produce energy in a process called oxidative metabolism. People use their skeletal muscles for movement, and therefore to be active requires oxidative metabolism by these muscles. The muscles need for oxygen led researchers to think that the low oxygen ("hypoxic") environments of spaceflight or future planetary worlds would impair function.
It is important to note that another study from the research group (the PlanHab Project), looking at whole-body exercise, found that hypoxia did in fact aggravate the impairment caused by microgravity alone. This suggests that the effects of hypoxia could be more significant during whole body exercise, in which the stress on the cardiovascular system is more pronounced. Bruno Grassi, the chief investigator on the project said: "This research will help prepare astronauts for spaceflight and it improves our understanding of how muscles respond to long periods of inactivity in association with hypoxia.
"Future studies will have to investigate in more detail the mechanisms responsible for the observed findings. The results obtained on skeletal muscles, moreover, will have to be interpreted in conjunction with those deriving from other studies of the PlanHab project, dealing with the cardiovascular, respiratory, immune and central nervous systems and metabolism."