Skip Navigation


Author(s): Joanne R. Lupton, PhD
Showing Results for: astronauts Return to Presentation

Consequences of the Muscle Atrophy Response

This illustration defines the cascade that one would expect to occur if some form of high loading activity is not routinely imposed on the space traveler exposed to the microgravity environment over long periods of time (months). Based on the scenario laid out in this figure, one would predict a low level of fitness in such an individual. Most individuals should perform various types of exercise on a routine basis on Earth, but the question is, what can be done to maintain the fitness and general health of anyone likely to be exposed to microgravity (or bed rest, for that matter) for long periods of time?

What types of activities would you recommend to ensure muscle homeostasis? Would you need special devices to bring this about?

Suggested Reading:
Baldwin, K. M., White, T. P., Arnaud, S. B., Edgerton, V. R., Kraemer, W. J., Kram, R., Raab-Cullen, D., & Snow, C. M. (1996). Musculoskeletal adaptations to weightlessness and development of effective countermeasures. Medicine and Science in Sports and Exercise. 28: 1247-1253.

The atrophy process creates what I refer to as “risk to muscle health” in response to the unloading state, whether we are talking about someone in space flight, or someone in a prolonged state of bed rest. There is a decrease in muscle mass, and a shift of the myosin phenotype from slow to fast contractile capabilities. In addition, the muscle becomes more fatigable when an individual engages in physical activity. So it is weaker, and it has less stamina. There is a general saying that, as the muscle goes, the bone goes. So when we start to atrophy muscle, the muscles are no longer putting stress on bone, and there is a loss in bone health. For an astronaut, and for an individual who is bed ridden, fitness falls dramatically. This person cannot do routine, normal things. Further, this condition creates ancillary health problems, one of the biggest being Type II diabetes.