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Metabolic Cost of Extravehicular Activities (SKYMET)
Principal Investigator
Research Area:
Cardiovascular physiology
Life support systems
Metabolism and nutrition
Species Studied
Scientific Name: Homo sapiens Species: Human

The prospect of pressure suit operations outside of space vehicles and on the lunar surface was the source of much speculation prior to Gemini. Predictions varied from the prospect of almost effortless activity to the fear that without the stabilization provided by earth's gravity useful activity would be very difficult. Experiments conducted during the Gemini Program indicated that extravehicular activities could be much more difficult and physically taxing than had been anticipated and that more emphasis should be placed in crew training and restraint technology.

The lunar portion of the Apollo Program presented entirely different extravehicular activity problems, i.e., 1/6-g and an unknown terrain. Indications were that the cost of walking would be reduced while the cost of other activities would be increased; however, the results and conclusions were by no means uniform. An additional factor of uncertainty was the terrain and surface composition of the Moon and its effect on the metabolic cost of walking. In response to these uncertainties, conservative biomedical estimates of the life support requirements were defined based on the available data, and methods to measure metabolic rate during the extravehicular activities were developed utilizing operational data from the life support system and bioinstrumentation.The objective of this Skylab experiment was to add additional data to the results obtained from the Gemini and Apollo experiments, and further quantify the metabolic expenditures associated with extravehicular activities.

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Waligora JM and Horrigan DJ. Metabolic Cost of Extravehicular Activities. In: Johnston RS, Dietlein LF, eds. Biomedical Results from Skylab. Washington, DC: NASA Headquarters; 1977:395-399. NASA SP-377. [NTRS]

Body temperature
Energy metabolism
Extravehicular activity
Life support systems
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Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
Data Sets+ Request data

Duration (hours)
Metabolic rate (kcal/h)

Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Skylab 2 05/25/1973 06/22/1973 28 days
Skylab 3 07/28/1973 09/25/1973 59.5 days
Skylab 4 11/16/1973 02/08/1974 84 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Hardware Items