Effects of repeated long duration +2Gz load on man's cardiovascular function

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Human Centrifuge Research

Background:

• Spaceflight leads to cardiovascular deconditioning and bone-calcium loss.
• Artificial gravity is a potential countermeasure, but optimal protocols are unknown.
• Orthostatic intolerance is a common post-flight issue linked to impaired baroreflexes.

Purpose of the Study:

• To analytically evaluate the effects of repeated long-duration +Gz load on human cardiovascular function.
• To assess the efficacy of artificial gravity as a countermeasure for spaceflight-induced deconditioning.
• To investigate changes in autonomic nervous system activity and baroreceptor sensitivity.

Main Methods:

• Utilized heart rate spectral analysis to quantify parasympathetic and sympathetic activity.
• Employed the sequence method to assess spontaneous baroreceptor reflex sensitivity (BRS).
• Studied 9 healthy men before and after 7 days of daily 1-hour +2Gz exposure.

Main Results:

• Significant increases in high-frequency power (HF-p), indicating enhanced parasympathetic activity.
• Statistically significant increase in baroreceptor reflex sensitivity (BRS).
• Trends towards decreased heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and low-to-high frequency ratio (LF/HF).

Conclusions:

• Repeated +2Gz loading enhances parasympathetic activity and arterial baroreceptor-cardiac reflex sensitivity.
• These findings suggest artificial gravity may be effective in preventing post-flight orthostatic intolerance.
• Daily artificial gravity exposure could mitigate cardiovascular deconditioning associated with space travel.