Without regular use, the muscles weaken and slowly deteriorate, a process called atrophy. Disuse also causes the bones to degenerate and weaken. In microgravity, the musculoskeletal system is not used as intensively as it is on Earth, which causes a reduction of bone and muscle strength and size, particularly in the bones and muscles that are used to support the body against gravity.
Muscle atrophy results in a loss of lean body mass, a decrease of muscle mass in gravity-bearing muscles, and decreased muscle strength. Bone demineralization results in a loss of calcium and bone density. To study the changes in bones and muscles in space, measurements of protein and calcium metabolism are made. Exposure to microgravity produces a negative calcium and nitrogen balance in the musculoskeletal system. Non-invasive imaging methods, like Magnetic Resonance Imaging (MRI), can be used to study the structural changes in bone and muscle after exposure to microgravity.
The long-duration Mir missions allowed researchers to use modern research methods to study the long-term effects of microgravity on the musculoskeletal system. Information gained from these investigations can be used to develop measures to prevent harmful or debilitating effects caused by long-term space flight, so that humans will be able to live and work in space for long periods in the future. Information gained from space-based research, like the muscle and bone experiments performed on Mir, can also be applied to improve the understanding of muscle and bone debilitation in common diseases like osteoporosis.
Bone Mineral Loss and Recovery after Shuttle-Mir Flights
Dynamics of Calcium Metabolism and Bone Tissue
Evaluation of Skeletal Muscle Performance and Characteristics (Phase 1A)
Evaluation of Skeletal Muscle Performance and Characteristics
Magnetic Resonance Imaging (MRI) after Exposure to Microgravity
Morphological, Histochemical and Ultrastructural Characteristics of Skeletal Muscle
Text only version available
page is best viewed with Microsoft Internet Explorer 4.0 or higher or Netscape
4.0 or higher.
Other viewing suggestions.
NASA Web Policy
Responsible NASA Official: John Uri
Page last updated: 07/16/1999