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Katherine K. Martin
Media Relations Office

August 23, 2006
RELEASE : 06-044
NASA and Cleveland Clinic Work to Keep Astronauts Strong
As NASA prepares to send humans back to the moon and out further into our solar system, researchers are looking for better ways to keep astronauts' bones and muscles strong.

Engineers at NASA's Glenn Research Center, and the Cleveland Clinic Lerner Research Institute's Biomedical Engineering Department, Cleveland, Ohio, have designed, built and are now testing subjects in the Enhanced Zero-gravity Locomotion Simulator (eZLS) to simulate how astronauts exercise during space travel. The eZLS utilizes principles developed for the zero-gravity locomotion simulator currently in use at Cleveland Clinic.

Glenn is collaborating with NASA's Exercise Countermeasures Project and Cleveland Clinic in a study during which test subjects walk and run on the eZLS while suspended by 20-foot cables hanging from the ceiling.

This study focuses on the design of the exercise harness that astronauts wear like a backpack while running on the International Space Station (ISS) treadmill. The key to the success of load-bearing exercise, such as treadmill running, is the application of gravity replacement loads to the crew member via a subject load device coupled to the body by a harness.

Astronauts are currently allotted up to 2.5 hours per day in exercise activities, including donning and doffing equipment. They typically log up to 30 minutes on the treadmill to help maintain fitness and mitigate effects of spaceflight deconditioning, including bone and muscle loss. However, crew feedback has indicated the harness frequently causes chafing and discomfort.

"In this study, we are using the eZLS to understand how we may help astronauts exercise more comfortably in space," said Gail Perusek, NASA Glenn project manager for the eZLS. "The end results of this study will help show us what design factors affect harness comfort, so we can build better equipment more suited to achieve the greatest benefit for crewmembers. The eZLS gives us a testbed to simulate weightlessness and optimize exercise countermeasure devices such as the harness. We can simulate partial gravity as well (i.e., the gravity on the moon, or one sixth that of the Earth), so the eZLS has relevance for lunar missions and beyond."

The prototype harness, developed by Cleveland Clinic utilizing backpack technology, and the most recent harness developed for astronauts by NASA will be evaluated to determine how they can best be used to optimize exercise performed and thereby maintain bone and muscle mass as well as cardiovascular health. This effort is being conducted through a consortium called the Center for Space Medicine, which provides a vehicle for collaborative research efforts by Glenn and the Clinic to address physiological issues associated with spaceflight.

Peter Cavanagh, Ph.D., D.Sc., chairman of the Clinic's Department of Biomedical Engineering and Co-Director of the Center, as well as head of the Bone Loss Team for the National Space Biomedical Research Institute, and his laboratory team designed the harness as a way to measure the benefits of exercise to combat bone loss both in space and on Earth.

For the current study, test subjects have been recruited from Glenn, its on-site contractors and the general public. Subjects have gone through extensive pre-screening to ensure they are fit to exercise in the simulator. Test subjects are then strapped into the harness and suspended from the ceiling while they walk or run in a horizontal position on a special vertical treadmill. In this position, there is no gravitational force between the runner and the machine. As on the treadmill used on the ISS, the subject wears the modified harness to which a system of motors and cables are attached at the waist that pull the runner toward the treadmill belt, exerting forces into the harness and on the bottom of the runner's feet that are measured by dozens of sensors.

NASA and Cleveland Clinic designed the eZLS so it would simulate the conditions on the ISS as accurately as possible. When astronauts exercise using the onboard treadmill, it is actually floating inside the vehicle. This lightens the load on the ISS and reduces vibrations that might disturb other experiments. As a result, the treadmill moves a little with the runner, which may limit the effectiveness of the exercise astronauts perform to keep healthy and strong.

To reproduce this floating effect, Glenn engineers added four bearings that look like hockey pucks to the bottom of the eZLS. These bearings have tiny holes that emit a thin film of air, causing the machine to float like a puck on an air hockey table. This hovering version more closely replicates the treadmill used in space.

The eZLS is part of Glenn's new Exercise Countermeasures Laboratory, which provides the capability of simulating in-flight or zero gravity, and surface or fractional gravity exercise to advance the health and safety of the next generation of space explorers. The eZLS is designed to allow development and validation of advanced exercise countermeasure devices, design, operational requirements and exercise prescriptions for mitigating the detrimental physiological effects of long-duration spaceflight. Glenn is also building a similar treadmill, the standalone Zero-gravity Locomotion Simulator, or sZLS, for use in bed rest studies at the University of Texas Medical Branch at Galveston, Texas. The first study will begin in 2007 with the goal of evaluating countermeasure hardware and prescriptions used on the ISS.

"The goals and objectives for future space exploration include creation of a new spacecraft, the Crew Exploration Vehicle, that will return humans to the moon, and eventually Mars and beyond," said Marsha Nall, manager of the Human Research Program at Glenn. "Addressing physiological deconditioning associated with spaceflight is a crucial part of this exploration vision."

For more information on the eZLS, visit

For more information on the Exercise Countermeasures Project, visit:


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