During spaceflight, astronauts are exposed to microgravity, which leads to deconditioning of the musculoskeletal and cardiovascular systems. Current methods of space exercise are not effective in preventing deconditioning. Lower body negative pressure refers to a technique in which the pressure exerted on the lower half of the body is less than that exerted on the upper half. In this study, microgravity is simulated by 30 days of bed rest in six degrees of head down tilt.
Exercise is performed while lying down partially inside a chamber.
The pressure in the chamber will be slowly reduced until it equals the force gravity exerts on your body while standing up. Exercise consists of running on an upright treadmill for 40 minutes six days a week. During the study we will test your muscle strength, exercise tolerance, ability to stand upright, balance and gait, sprint speed, spinal compression, bone density, gastrointestinal function, sleep quality, knee ligament laxity, intracranial pressure, brain blood flow, arterial elasticity, and changes in daily weight. Most of these measures are done noninvasively. Plasma volume and serum bone markers will require blood draws to be done weekly throughout the study.