Cardiovascular deconditioning in microgravity: some possible countermeasures

Abstract

Microgravity is an extreme environment inducing relevant adaptive changes in the human body, especially after prolonged periods of exposure. Since the early sixties, numerous studies on the effects of microgravity, during manned Space flights, have produced an increasing amount of information concerning its physiological effects, globally defined "deconditioning". Microgravity deconditioning of the cardiovascular system (CVD) is briefly reviewed. It consists of: (1) a decrease of circulating blood and interstitial fluid volumes, (2) a decrease of arterial blood diastolic pressure, (3) a decrease of ventricular stroke volume, (4) a decrease of the estimated left ventricular mass and (5) resetting of the carotid baroreceptors. The negative effects of microgravity deconditioning manifest themselves mostly upon the reentry to Earth. They consist mainly of: (1) dizziness, (2) increased heart rate and heart palpitations, (3) an inability to assume the standing position (orthostatic intolerance), (4) pre-syncopal feelings due to postural stress and (5) reduced exercise capacity. To avoid these drawbacks several countermeasures have been proposed; they will be briefly mentioned with emphasis on the "Twin Bikes System" (TBS). This consists of two coupled bicycles operated by astronauts and counter-rotating along the inner wall of a cylindrical Space module, thus generating a centrifugal force vector, mimicking gravity.

Electrical Stimulation of Acupuncture Points and Blood Pressure Responses to Postural Changes: A Pilot Study

“…Positional change is an intervention that is known to disturb hemodynamic status, 22,23 particularly in patients who are critically ill. A body position cycle of supine to -10º headdown and return to supine position was used to induce a cardiovascular challenge in this study. Gravity has a significant effect on the physiological response of the cardiopulmonary system, 24 and an increase in gravitational forces can markedly affect cardiac output and respiratory work. 25,26 Usually, when a person's position is changed from supine to head-down, venous return to the heart will initially increase in response to the hydrostatic effect and subsequently stroke volume, cardiac output, and blood pressure increase.…”

Spaceflight results in increase of thick filament but not thin filament proteins in the paramyosin mutant of Caenorhabditis elegans

“…One of the most affected is the neuromuscular system. Weightlessness induces atrophy of skeletal muscle (Riley et al, 1987;Widrick et al, 1999) and cardiovascular deconditioning (Philpott et al, 1990;Antonutto and Prampero, 2003). Weightlessness also reduces functional capacity in limb skeletal muscle of animals including humans (Ilyina-Kakueva et al, 1976;Widrick et al, 1999;Fitts et al, 2000).…”

The energetics of cycling on Earth, Moon and Mars

“…Since the early years of the Space Era, it was clear that prolonged exposure to microgravity induced a series of consequences at the cardiocirculatory level which were globally defined as Cardio Vascular Deconditioning (CVD) (Antonutto and di Prampero 2003). Therefore, scientists have studied and tested different countermeasures to prevent both CVD and reduced exercise capacity.…”