Microgravity decreases heart rate and arterial pressure in humans

TLDR

Spaceflight induces cardiovascular adaptations such as postflight orthostatic intolerance, but in‑flight data are scarce and inconsistent. The study aimed to determine normative in‑flight changes in heart rate, arterial pressure, and cardiac rhythm in Shuttle astronauts. Heart rate, arterial pressure, and rhythm were measured continuously over 24‑hour periods before, during, and after flight while astronauts performed normal routines. During flight, heart rate, diastolic pressure, their variability, and premature ventricular contractions were significantly reduced, with systolic pressure and premature atrial contractions also tending to decrease, indicating microgravity does not chronically stress the cardiovascular system.

Abstract

Spaceflight causes adaptive changes in cardiovascular physiology, such as postflight orthostatic intolerance, that can have deleterious effects on astronauts. In-flight cardiovascular data are difficult to obtain, and results have been inconsistent. To determine normative in-flight changes in Shuttle astronauts, we measured heart rate, arterial pressure, and cardiac rhythm disturbances for 24-h periods before, during, and after spaceflight on Shuttle astronauts performing their normal routines. We found that heart rate, diastolic pressure, variability of heart rate and diastolic pressure, and premature ventricular contractions all were significantly reduced in flight. Systolic pressure and premature atrial contractions also tended to be reduced in flight. These data constitute the first systematic evaluation of in-flight changes in basic cardiovascular variables in Shuttle astronauts and suggest that a microgravity environment itself does not present a chronic stress to the cardiovascular system.