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. However, they found that inactivity itself may have a more pronounced effect on skeletal muscle than a lack of oxygen.
Results - Impairments - Microgravity - Hypoxia - Inactivity
The results demonstrated that the impairments following microgravity were not aggravated by hypoxia. Given that inactivity and hypoxia are frequently associated with several important cardiovascular and respiratory diseases there is a suggestion that for skeletal muscle, inactivity is worse compared to hypoxia. If confirmed, this finding would have obvious relevant consequences on therapeutic and rehabilitative interventions: correction of hypoxia could be less critical than correction of inactivity.
As well as for astronauts, this research could have a significant impact...
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