Physiological Performance

There have been proposals over the years for centrifuge modules on the ISS to study artificial gravity. Image Credit: Mark Holderman/NASA.

Astronauts experience a strong physiological deconditioning during space missions, primarily due to the weightless conditions. Some of these adverse consequences include bone loss, muscle atrophy, sensory-motor/vestibular deconditioning, visual impairment, and overall cardiovascular adaptation, which may lead to orthostatic intolerance when astronauts are exposed again to a gravitational environment. Physiological deconditioning will be even more challenging in future long-duration space missions, for example to Mars, in which astronauts will be exposed to weightlessness for six to eight months before landing without external help to support egress. In order to mitigate these negative effects, several countermeasures are currently in place, particularly very intensive exercise protocols. However, despite these countermeasures, physiological deconditioning still persist to a certain degree, highlighting the need for new approaches to maintain the astronauts’ physiological state within acceptable limits.

Artificial gravity (generated by centrifugation) has long been suggested as a comprehensive countermeasure that is capable of challenging multiple physiological systems at the same time, therefore maintaining overall health during extended weightlessness. However, human centrifuges hasn’t been tested in space, and there are still many questions about its implementation (including centrifuge configuration, exposure time, gravity level, gravity gradient, and use/intensity of exercise, etc). We want to investigate these research questions using a combination of human experiments on ground-based centrifuges and modeling techniques of physiological systems to complement the experimental results.

Astronauts experience physiological deconditioning in space due to the extended exposure to microgravity including, but not limited to, muscle atrophy, loss of strength, and bone loss. Current countermeasures on the International Space Station include resistance training as well as aerobic exercises, and the use of the Advance Resistive Exercise Device (ARED) has been effective in reducing spaceflight musculoskeletal deconditioning. However, the ARED is a bulky device and compact devices that minimize mass and volume are necessary for use within the new space exploration vehicles. In collaboration with NASA Ames, we are investigating exercise performance on the Hybrid Ultimate Lifting Kit (HULK), a new lighter and more compact exercise device under development.