Heart Rate and Daily Physical Activity with Long-Duration Habitation of the International Space Station

Abstract

We investigated the pattern of activity and heart rate (HR) during daily living on the International Space Station (ISS) compared to on Earth in 7 long-duration astronauts to test the hypotheses that the HR responses on the ISS would be similar to preflight values, although the pattern of activity would shift to a dominance of arm activity, and postflight HR would be elevated compared to preflight during similar levels of activity. HR and ankle and wrist activity collected for 24-h periods before, during, and after spaceflight were divided into night, morning, afternoon, and evening segments. Exercise was excluded and analyzed separately. Consistent with the hypotheses, HR during daily activities on the ISS was unchanged compared to preflight; activity patterns shifted to predominantly arm in space. Contrary to the hypothesis, only night time HR was elevated postflight, although this was very small (+4 +/- 3 bpm compared to preflight). A trend was found for higher postflight HR in the afternoon (+10 +/- 10 bpm) while ankle activity level was not changed (99 +/- 48, 106 +/- 52 counts pre- to postflight, respectively). Astronauts engaged in aerobic exercise 4-8 times/week, 30-50 min/session, on a cycle ergometer and treadmill. Resistance exercise sessions were completed 4-6 times/week for 58 +/- 14 min/session. Astronauts on ISS maintained their HR during daily activities; on return to Earth there were only very small increases in HR, suggesting that cardiovascular fitness was maintained to meet the demands of normal daily activities.