NASA's eZLS Treadmill Promotes Astronaut Fitness

By: Emily Groh

Physical fitness is just as important in space as it is on Earth. Space fitness is even more vital since astronauts are more susceptible to health problems including the accelerated loss of bone and muscle mass. Without gravity, muscles and bones weaken since they are not required to perform like they do on Earth. To date, the exercise prescriptions used for aerobic and muscular resistance training have not been effective in space.

In an effort to help develop improved exercise routines and equipment for crew members, the Human Health and Performance Program at NASA Glenn is currently constructing the Enhanced Zero Gravity Locomotion Simulator (eZLS) in association with the Cleveland Clinic Foundation (CCF). This work has been funded both by NASA and the National Space Biomedical Research Institute (NSBRI).

Construction of the structure will continue through the fall while testing with human subjects is scheduled to begin by the end of December 2005. Along with the simulator, an analytical model is being developed to incorporate the physical dynamics of the eZLS, which will make it easier to study the effects of treadmill exercise on the human body and on the space vehicle.

The eZLS combines a treadmill that floats on a thin film of air and a supine suspension system, which simulates a zero-gravity environment by completely offloading the weight of a human subject's head, torso, arms, and legs. The test subject is suspended horizontally so the body remains weightless with respect to the running surface, until a controllable “gravity replacement load” is applied to his/her body via a constant-force system that connects to a backpack-like harness worn by the test subject.

The treadmill's running surface is mounted vertically in a free-standing frame as if the subject were running against the wall. The eZLS is designed for ground-based experiments to gain insight into the forces acting on the body, so that more efficient exercise prescriptions may be developed to help astronauts maintain a healthy level of fitness. In addition to running and walking, the eZLS will eventually be able to simulate cycling, resistance training, and jumping exercises.

Prior to becoming a project at Glenn in February 2004, Zero Gravity Locomotion Simulators were developed at Penn State University and the CCF. Headed by biomedical researcher, Peter R. Cavanagh, Ph.D., the Center for Space Medicine was formed to combine the biomedical engineering efforts of CCF and Glenn. Commenting on the significance of the eZLS, Project Lead, Gail Perusek, said, “This project presents a rare opportunity for GRC to work with human test subjects in a ground-based simulation. Also, this is the first NSBRI research funded and conducted at GRC.”

Improved exercise programs would greatly benefit astronauts who can experience bone/muscle mass loss at accelerated rates while in space unless appropriate countermeasures are instituted. According to Perusek, in spite of a 2-hour period assigned each day for exercise on the International Space Station, some astronauts still lose from 1% to 1.5% of their bone mass in key regions (such as the hip and lumbar spine) per month – approximately the amount of bone mass a post-menopausal woman can lose in one year. Studies published by NASA Johnson on nasa.gov reveal that astronauts can lose up to 20% muscle mass during a 5-11 day space flight. NASA researchers will continue to study both the short-term and long-term effects of bone/muscle mass loss on the astronaut's body once he/she returns to Earth.

Aside from space applications, experiments conducted using the eZLS may help medical researchers develop methods to help prevent osteoporosis in people living on Earth, as the mechanism of bone and muscle loss on Earth is very similar. The eZLS will be used to support future missions related to the Vision for Space Exploration.

It may be used to help specify design requirements for the exercise equipment on the Crew Exploration Vehicle (CEV) and simulate planetary locomotion in partial gravity environments including Moon and Mars. The facility will also be available to researchers working on NASA's new Exercise Countermeasure Project being led by Johnson.