Archived by Raymond J. Noonan, Ph.D., Health and Physical Education Department, Fashion Institute of Technology of the State University of New York (FIT-SUNY), and SexQuest/The Sex Institute, NYC, for the benefit of students and other researchers interested in the human aspects of the space life sciences. Return to first page for background information on these pages.
THE MUSCULOSKELETAL SYSTEM
There is no doubt that gravity has shaped the architecture of the human body -- its more than 600 muscles and 200 bones. So it should come as no surprise that gravity is required for the "Earth-normal" functioning of the musculoskeletal system. Without gravity, muscles waste away, and bones become smaller and weaker. Medical doctors have observed these effects in bed-rest patients whose movement and exercise have been limited; to a certain extent, these same effects have also been observed in space-flight crews. In microgravity, leg muscles can become weakened from lack of use, because astronauts can "float" instead of walk. Such weakening results from a loss of muscle mass in the calves and lower body, and decreased muscle strength. This decrease in size and strength is referred to as muscle atrophy.Weightlessness also causes a slow loss of bone minerals (calcium and phosphorous). Crew members from previous long-duration U.S. flights have shown such a loss throughout their missions (up to 84 days in duration). Most of the loss is thought to occur in the leg bones and spine which are responsible for erect posture and locomotion. So far, it is not known whether the body would continue to lose calcium indefinitely or whether the loss would stop at a certain point. To date, exercise regimens have not reduced the loss of calcium. An understanding of the time course, extent, and mechanisms for muscle and bone alterations is critical to determining how long humans may safely remain in space and what can be done to halt negative effects. Development of effective countermeasures to bone loss in space may contribute to improved therapy or management of osteoporosis. Osteoporosis, the most prevalent clinical bone disorder on Earth, is a condition in which bone mass becomes porous, brittle, and prone to fracture. Abnormalities in calcium balance observed during space flight are similar to those seen in patients with osteoporosis.
Countermeasures
Muscle loss can be countered by in-flight exercises on an exercycle or a rowing machine, but countering bone loss requires more force than a human can comfortably exert in microgravity using the exercise devices flown in space so far. There may be drugs which can prevent bone loss in space, but NASA hasn't found a solution to this problem yet. (Can you?)
Questions
- You can go back to where you came from, or jump back to the beginning.
- Select here for more details on bone mineral loss in space.
- The next section is about the neurovestibular system.
Last modified: Dec 21, 1994Author: Ken Jenks
Raymond J. Noonan, Ph.D. Health and Physical Education Department Fashion Institute of Technology of the State University of New York (FIT-SUNY); SexQuest/The Sex Institute, NYC P.O. Box 20166, New York, NY 10014 (212) 217-7460 |
Author of: R. J. Noonan. (1998). A Philosophical Inquiry into the Role of Sexology in Space Life Sciences Research and Human Factors Considerations for Extended Spaceflight. Dr. Ray Noonan’s Dissertation Information Pages: [Abstract] [Table of Contents] [Preface] [AsMA 2000 Presentation Abstract] |
First published on the Web on June 14, 1998