Physiological Changes in the Cardiovascular System During Space Flight　- Current Countermeasures and Future Vision

With the recent acceleration of manned space exploration, health care in space has become an important issue. Cardiovascular problems, mainly caused by the microgravity environment in space, include decreased red blood cell volume, myocardial atrophy and aerobic capacity, and reduced orthostatic tolerance after return. However, complete physiological countermeasures have not been established and more research is needed.

A search on PubMed was conducted for English-language articles on cardiovascular changes in space and their countermeasures and post return rehabilitation. Early in space flight, diuresis associated with fluid shifts causes changes in erythrocyte volume, and after prolonged stays, the vestibular and cardiocirculatory systems are induced to show orthostatic intolerance due to decreased blood pressure increasing reflexes, decreased circulating plasma volume, and myocardial atrophy. The main countermeasures include aerobic exercise and strength training in space 6 days a week, for approximately 2 h a day, and a rehabilitation program after return to re-adapt to the Earth's gravitational environment.

In the near future, when people with heart disease and the elderly will fly in space, new health management techniques that combine the knowledge accumulated in space flight and cardiac rehabilitation on the ground will be necessary for in-flight countermeasures against cardiovascular changes in space and for post-return rehabilitation.