Artificial gravity training reduces bed rest-induced cardiovascular deconditioning

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Human Physiology

Background:

• Prolonged bed rest leads to cardiovascular deconditioning, including reduced plasma volume and aerobic capacity.
• Orthostatic intolerance is a significant challenge for individuals subjected to bed rest, impacting cardiovascular regulation.
• Artificial gravity (AG) is being investigated as a potential countermeasure for spaceflight-induced physiological deconditioning.

Purpose of the Study:

• To determine if daily artificial gravity (AG) exposure can prevent cardiovascular deconditioning caused by 21-day head-down tilt bed rest.
• To assess the effects of AG on cardiac function, plasma volume, aerobic power, and neuroendocrine responses.
• To evaluate cardiovascular and neuroendocrine adaptations to orthostatic stress after bed rest with and without AG.

Main Methods:

• Fifteen men underwent 21 days of 6° head-down tilt bed rest, with 8 receiving daily 1-hour exposures to 1.0 G(z) artificial gravity (AG).
• Cardiovascular assessments included echocardiography, plasma volume measurements, and aerobic power (VO(2)pk) testing.
• Responses to 80° head-up tilt (HUT) were measured, including ECG, stroke volume (SV), blood pressure (BP), and blood for catecholamines and vasoactive hormones.

Main Results:

• Bed rest reduced plasma volume, stroke volume, and cardiac function in both control and AG groups.
• AG attenuated the decrease in orthostatic tolerance and aerobic power (VO(2)pk) compared to the control group.
• AG prevented increases in plasma renin activity and angiotensin II, while enhancing aldosterone and norepinephrine responses during HUT post-bed rest.

Conclusions:

• Daily artificial gravity (AG) exposure can mitigate certain aspects of bed rest-induced cardiovascular deconditioning.
• AG effectively improved orthostatic tolerance and preserved aerobic power.
• The beneficial effects of AG appear to be mediated by improved sympathetic responsiveness rather than direct cardiac effects.