Hughson, R., Shoemaker, J., Blaber, A, et al. (2012). Cardiovascular regulation during long-duration spaceflights to the International Space Station. Journal of Applied Physiology, 112(5):719-27 Details
Customer study highlights
One concern with spaceflight is that, in the absence of gravity, cardiovascular deconditioning may gradually occur. Observational studies of astronauts living on the International Space Station (ISS) and Russian MIR space station have reported some impairment in blood pressure (BP) regulation, for example, in the baroreceptor reflex regulation of BP in response to standing. However, further study of baroreflex function is required upon return to Earth after long durations in space.
In the present study, arterial baroreflex activity was monitored in six male astronauts (41-55 yrs) carrying out missions on board the ISS for up to 180 days. Arterial blood pressure variation in response to normal and paced breathing was monitored pre- and post-flight with a Finapres non-invasive blood pressure (NIBP) device and a PowerLab, and a NASA BP device whilst in space.
No significant changes in heart rate (HR), BP or baroreflex responses were found between pre-flight and in-flight data. However, HRV analysis revealed a reduction in high frequency spectral power mid- and post-flight suggesting some loss of parasympathetic control of HR. In itself, this is not indicative of cardiac deconditioning.
Back on Earth, a post-flight increase in HR (5-6 bpm) and a small increase in cardiac output (0.6 L/min) were found. Baroreflex response slopes were reduced by 34%.
Overall, this study shows very little cardiac deconditioning during lengthy periods in space, suggesting that exercise undertaken by astronauts in the current space program is sufficient to counteract this. However, the major stressor is the return to a gravity-laden Earth.