Effect of Spaceflight On The Human Body - List of Effects of Space On Human Physiology - The Effects of Weightlessness - Loss of Bone and Muscle Mass

Loss of Bone and Muscle Mass

A major effect of long-term weightlessness involves the loss of bone and muscle mass. Without the effects of gravity, skeletal muscle is no longer required to maintain posture and the muscle groups used in moving around in a weightless environment differ from those required in terrestrial locomotion. In a weightless environment, astronauts put almost no weight on the back muscles or leg muscles used for standing up. Those muscles then start to weaken and eventually get smaller. Consequently some muscles atrophy rapidly, and astronauts can lose up to 25% of their muscle mass on long flights. The types of muscle fibre prominent in muscles also change. Slow twitch endurance fibres used to maintain posture are replaced by fast twitch rapidly contracting fibres that are insufficient for any heavy labour. Advances in research on exercise, hormone supplements and medication may help maintain muscle and body mass.

Bone metabolism also changes. Normally, bone is laid down in the direction of mechanical stress, however in a microgravity environment there is very little mechanical stress. This results in a loss of bone tissue approximately 1.5% per month especially from the lower vertebrae, hip and femur. Elevated blood calcium levels from the lost bone result in dangerous calcification of soft tissues and potential kidney stone formation. It is still unknown whether bone recovers completely. Unlike people with osteoporosis, astronauts eventually regain their bone density. After a 3-4 month trip into space, it takes about 2–3 years to regain lost bone density. New techniques are being developed to help astronauts recover faster. Research on diet, exercise and medication may hold the potential to aid the process of growing new bone.

To prevent some of these adverse physiological effects, the ISS is equipped with two treadmills (including the COLBERT), and the aRED (advanced Resistive Exercise Device), which enable various weight-lifting exercises which add muscle but do nothing for bone density, and a stationary bicycle; each astronaut spends at least two hours per day exercising on the equipment. Astronauts use bungee cords to strap themselves to the treadmill. Astronauts subject to long periods of weightlessness wear pants with elastic bands attached between waistband and cuffs to compress the leg bones and reduce osteopenia.

Read more about this topic:  Effect Of Spaceflight On The Human Body, List of Effects of Space On Human Physiology, The Effects of Weightlessness

Famous quotes containing the words loss of, mass, loss and/or bone:

    Upset at the young wife’s
    first loss of virtue
    in a riverside thicket,
    a flock of birds
    flies up,
    mourning the loss
    with their wings.
    Hla Stavhana (c. 50 A.D.)

    The mass are animal, in pupilage, and near chimpanzee.
    Ralph Waldo Emerson (1803–1882)

    ... imprisonment itself, entailing loss of liberty, loss of citizenship, separation from family and loved ones, is punishment enough for most individuals, no matter how favorable the circumstances under which the time is passed.
    Mary B. Harris (1874–1957)

    You must be wise, in order to sniff out and weigh these mighty books, and swift in the hunt and brave in the battle; then, by careful reading and frequent reflection, crack open the bone and suck out the substantific marrow.
    François Rabelais (1494–1553)