Foot Ground Reaction Forces During Spaceflight FOOT

Principal Investigator: Peter R. Cavanagh, Ph.D., Chairman, Department of Biomedical

Engineering, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio

Without appropriate countermeasures, astronauts traveling in space can lose as much bone mineral in the lower extremity in one month as a typical post-menopausal woman looses in an entire year. Muscle strength can also be lost rapidly during spaceflight. Such decrements as a result of prolonged exposure to microgravity have important implications for performance and safety during space missions and thus the identification of mechanisms and countermeasures for such changes are a high priority for NASA.

It is widely believed that changes in bone and muscle are directly related to the decrease in mechanical loading. This hypothesis is supported by the fact that little or no bone mineral is usually lost from the upper extremity - which may be even more frequently used in orbit than it is on the ground. The objective of the experiment called FOOT is to quantify and explore the relationship between loading of the human body and changes in the musculoskeletal system during spaceflight.

The principal investigator on the experiment, Peter R. Cavanagh, Ph.D., has previously been involved with the design of the Human Research Facility in the space station and in the evaluation of the treadmill vibration isolation system (TVIS) that is used for exercise on the International Space Station (ISS).

Experiment Operations

FOOT will accomplish its objectives through direct measurement of forces on the feet, joint angles and muscle activity in astronauts during typical entire days of daily life both on Earth and on the ISS. In addition, bone mineral density, muscle strength, and muscle volume will be measured before and after the mission.

The heart of the FOOT experiment is an instrumented suit called the Lower Extremity Monitoring Suit (LEMS) (see sketch below). This customized garment is a pair of Lycra cycling tights incorporating 20 carefully placed sensors and the associated wiring, control units, and amplifiers. LEMS will enable the electrical activity of muscles, the angular motions of the hip, knee, and ankle joints, and the force under both feet to be measured continuously. Information from the sensors can be recorded for up to 14 hours on a small wearable computer. Measurements will also be made on the arm muscles. The


National Aeronautics and Space Administration

National Aeronautics and Space Administration crewmembers will put the suit on in the morning before they start their work day and, after calibration, they will go about their regular daily activities. Throughout the day, the sensors will capture data that will allow researchers to characterize differences between use of the arms and legs on Earth and in space.

Before launch and after landing, DXA scans, MRIs, and Cybex testing will be used to measure the changes in bone mineral density, muscle volume, and muscle strength, respectively. Researchers will relate these changes to the measurements made from the LEMS.

The first subject who will perform the experiment on the ISS will be Ken Bowersox, commander of Expedition 6. 1G Baseline data has already been collected from Commander Bowersox who is fully trained in procedures for the experiment. Members of the Expedition 8 crew, astronauts Mike Foale and Bill McArthur, are currently undergoing training for the experiment.

FOOT has the potential to shed significant new light on the reasons for bone and muscle loss during spaceflight and on the design of exercise countermeasures. The data should allow the "dose" of mechanical load to be chosen based on the measurements performed in the study. Ideally, exercise countermeasures should replace the critical mechanical input that is present on Earth but missing in space. The ISS environment offers an ideal setting in which the experimental hypothesis can be examined. In addition, the theories that are to be explored in this project have significance for understanding, preventing, and treating osteoporosis on Earth, which is a major public health problem.


National Aeronautics and Space Administration
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