Abstract
The use of short-arm centrifugal system (SACS) could be one of the best means for the prevention of several physiological problems including cardiovascular deconditioning (CVD) caused by a prolonged exposure to microgravity. The CVD consists of: 1) hypovolemia, 2) a decrease of diastolic blood pressure, 3) a decrease of stroke volume, 4) a decrease of left ventricular mass, and 5) resetting of the carotid baroreceptors. The CDV appears as: 1) dizziness, 2) increased heart rate, 3) orthostatic intolerance, 4) presyncopal feeling, and 5) reduced exercise capacity. First, we should establish a prescription (the strength, length, and frequency) of artificial gravity loads using the SACS. We studied the effect of the SACS as a countermeasure on the prevention of the CVD during 4 days of 6° head-down bed rest (HDBR). Half of 20 young healthy subjects was loaded total gravity of +2Gz twice a day (up to 30min×2) during the HDBR period. R-R intervals and continuous blood pressures were simultaneously measured at supine position prior to the HDBR and immediately after the HDBR. Previous reports have indicated that prolonged weightlessness impaired the baroreceptor reflex responses and vagal modulation to heart rate. Our result suggests that daily loading to 2Gz-1hr can lessen the changes in autonomic cardiovascular control during the exposure to microgravity, and consequently might be useful for the prevention of CVD. The periodic loads couldn't prevent a decrease in exercise capacity. Therefore, exercises during the centrifugal loading are needed. [Jpn J Physiol 54 Suppl:S45 (2004)]
