Athletes, astronauts and orthostatic tolerance

Area of Science:

• Exercise Physiology
• Space Medicine
• Autonomic Function

Background:

• Endurance training may alter autonomic functions, potentially reducing orthostatic tolerance.
• This raises concerns about endurance-trained athletes' suitability for spaceflight due to blood pooling.
• Existing evidence on this link is conflicting and not widely published.

Purpose of the Study:

• To evaluate the hypothesis that endurance training reduces orthostatic tolerance.
• To assess the potential impact of endurance training on astronaut selection criteria.
• To clarify the relationship between aerobic power and orthostatic tolerance.

Main Methods:

• Review of existing literature on endurance training and orthostatic stress.
• Analysis of data from spaceflight and simulated weightlessness studies (e.g., water immersion).
• Consideration of physiological differences between endurance athletes and non-athletes.

Main Results:

• Some studies (e.g., water immersion) suggest reduced orthostatic tolerance in endurance athletes after simulated weightlessness.
• Other published studies refute the hypothesis linking endurance training to reduced orthostatic tolerance.
• Conflicting evidence necessitates further investigation.

Conclusions:

• The current information is inadequate to definitively state a relationship between aerobic power and orthostatic tolerance.
• More research is needed to resolve conflicting findings and inform astronaut selection.
• Physiological differences between athletes and non-athletes warrant continued exploration of this hypothesis.