Evaluation of Maximal Oxygen Uptake and Submaximal Estimates of VO2max Before, During, and After Long Duration International Space Station Missions (VO2max) - 07.29.14
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Evaluation of Maximal Oxygen Uptake and Submaximal Estimates of VO2max Before, During, and After Long Duration International Space Station Missions (VO2max) documents changes in maximum oxygen uptake for crewmembers on board the International Space Station (ISS) during long-duration missions.
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Elite athletes know their VO2max, which measures aerobic capacity and is directly related to the amount of physical exertion someone can achieve. In space, VO2max relates to a crew member's ability to work outside the spacecraft while wearing a space suit and to respond to an in-flight emergency. Researchers documented changes in maximum oxygen uptake for ISS crew members during long-duration missions and found that VO2max declines at the beginning of a flight and slowly recovers during flight. However, not all crew members return to preflight levels and vary substantially in their responses. These results help to tailor extravehicular activities and guide adjustments to exercise countermeasures on future missions.
European Space Agency (ESA), Noordwijk, , Netherlands
Johnson Space Center, Human Research Program, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2009 - March 2013
Previous ISS Missions
VO2max began operations during ISS Expedition 19/20.
- Evaluation of Maximal Oxygen Uptake and Submaximal Estimates of VO2max Before, During, and After Long Duration International Space Station Missions (VO2max) allows for measurement of actual VO2max as opposed to the estimation methodology previously used in order to gain more insight into the aerobic capacities of the crewmembers on board the ISS.
- VO2max, sometimes referred to as VO2peak, is the standard measure of aerobic capacity and is directly related to the physical working capacity of an individual. VO2max is related to the ability to perform an egress task while wearing a Launch and Escape space suit; therefore, decreased VO2max may represent a safety concern in the event of an emergency during space flight.
- By understanding the changes in VO2max that occur within space flight, necessary adjustments can be made to extravehicular activity (EVA) exercise countermeasures.
In 2006, National Aeronautics and Space Administration (NASA) identified gaps in the scientific and medical knowledge regarding the human response to space flight. One of the gaps was the direct measurement of maximum oxygen uptake (VO2max) during and after long-duration space flight. Reduced VO2max causes a diminished capacity to perform strenuous physical tasks such as those required during extended extravehicular activities (EVAs) while performing structure assembly tasks. VO2max has never been assessed during or after long-duration space flight, nor have the estimation methods currently used by NASA to track changes in aerobic fitness during space flight been validated on orbit. Therefore, the VO2max investigation measures VO2max during and following long-duration missions and assesses the validity of using submaximal measurements of heart rate (HR) and oxygen consumption (VO2) to track changes in aerobic capacity. In addition, non-invasive measurements of cardiac output (Qc) are performed during exercise to determine if measurement of Qc will improve the accuracy of the submaximal estimations of VO2max.
For this investigation, crewmembers participating in the ISS missions greater than or equal to 90 days perform graded cycle exercise tests to maximum effort levels prior to, every 30 days during, and following flight. Measurements obtained during these tests include HR, VO2, and Qc. During these tests, electrocardiogram (ECG) is monitored real-time as a safety precaution.
It is expected that the results from the VO2max investigation include accurate VO2max measurements from crewmembers participating in long-duration space flight and observation of the pattern of change across mission duration. Additionally, the evaluation allows NASA to determine if submaximal exercise testing data provides results that allow accurate estimation of the crewmembers’ aerobic capacity during and after space flight. Data from this experiment is shared with NASA Medical Operations to refine future test requirements and optimize the testing used to track aerobic capacity during and after space flight.
The results from this experiment provide NASA and the ISS International Partners definitive data to determine if submaximal exercise testing provides an accurate assessment of aerobic capacity during and following long-duration space flight.
The data obtained from this study provides valuable insight into the aerobic capacity of teams in closed environments on Earth, such as arctic bases and submarines.
The VO2 max experiment requires a subject count of 12. The preflight portion occurs at Launch minus 270 (L-270) days and L-60 with a back-up preflight session at L-30, if required. The inflight portion begins on Flight Day 15 and repeats every 30 days for the duration of the increment. There is a postflight portion occurring at Return plus 1 (R+1) and R+10 with a possible R+30 session pending crew surgeon and investigator discretion. There is a requirement for real-time data downlink during the exercise protocol.
Preflight activities begin at Launch minus 270 (L-270) days, whereby an upright cycle ergometer test establishes peak heart rate and VO2. Additional measures include blood pressure, workload, and perception of effort. The values obtained from this test establish the work rates for all further testing sessions. The L-60 test serves as the first test the subject performs using their specific protocol. Measures of VO2, VCO2, heart rate, Qc, blood pressure, workload and rating of perceived exertion are obtained. If the data from this test is judged not technically acceptable, this test is repeated at L-30. Exercise logs are obtained at L-180 and from L-90 until flight.
Inflight activities occur on Flight Day (FD) 15 and every 30 days thereafter. Crewmembers set up the Portable Pulmonary Function System (PPFS), Cycle Ergometer with Vibration Isolation and Stabilization (CEVIS), and associated hardware. The crewmember exercises using the CEVIS and inspires (inhales) cabin air and expires (exhales) through a mouthpiece while their nostrils are occluded with a nose clip. The PPFS is used to calculate or monitor VO2, VCO2, heart rate, Qc, blood pressure, and workload. Real-time data downlink is required during the exercise protocol. Health and status data are acquired real-time depending on Frequency Sub-Band (Ku) coverage; otherwise, all data is stored on the PPFS for downlink following the session.
Postflight activities begin at Return plus 1 (R+1) day. Tests identical to the preflight L-60 and L-30 tests are performed. Measurements include VO, VCO2, heart rate, Qc, blood pressure, workload and rating of perceived exertion. The test performed on R+10 is identical to tests performed at L-60, L-30, and R+1. The final test performed at R+30 is identical to tests performed at L-60, L-30, R+1 and R+10. This test is waived by the investigator and crew surgeon if data obtained from the R+10 session indicates the crewmember’s aerobic capacity has returned to preflight levels.
Preliminary Results: VO2max declines very early upon arrival to microgravity and slowly recovers during flight, but the mean change for all subjects tested does not recover to preflight levels. The mean change in VO2max on R+1 is -14%. This is not significantly different than that observed during the last flight test. A substantial amount of variability exists between subjects in their responses during flight. Submaximal estimates of VO2max do not reliably track change in actual VO2max.
Moore Jr. AD, Moore Jr. AD, Everett M, Lee SM, Lee SM, Feiveson AH, Knudsen P, Ploutz-Snyder LL. Peak exercise oxygen uptake during and following long-duration spaceflight. Journal of Applied Physiology. 2014 June 26; epub.
Ground Based Results Publications
Lee SM, Lee SM, Moore Jr. AD, Moore Jr. AD, Barrows LK, Fortney SM, Greenisen MC. Variability of Prediction of Maximal Oxygen Consumption on the Cycle Ergometer Using Standard Equations. NASA Technical Publication; 1993.
Levine BD, Lane LD, Watenpaugh DE, Gaffney FA, Buckey, Jr. JC, Blomqvist CG. Maximal exercise performance after adaptation to Microgravity. Journal of Applied Physiology. 1996; 81(2): 686-94.
Lee SM, Lee SM, Moore Jr. AD, Moore Jr. AD, Barrows LK, Fortney SM, Greenisen MC. NASA TP 3412, Variability of Prediction of Maximal Oxygen Consumption on the Cycle Ergometer Using Standard Equations. NASA Technical Publication; 1993.
Moore Jr. AD, Moore Jr. AD, Lee SM, Lee SM, Charles JB, Greenisen MC, Schneider SM. Maximal exercise as a countermeasure to orthostatic intolerance after spaceflight. Medicine and Science in Sports and Exercise. 2001; 33(1): 75-80.
ISS Medical Project
NASA Image: ISS030E007540 - Astronaut Dan Burbank, Expedition 30 Commander, using the Portable Pulmonary Function System,(PPFS) hardware while exercising on the Cycle Ergometer with Vibration Isolation and Stabilization (CEVIS) in the U.S. Laboratory.
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NASA Image: ISS026E029180 - NASA astronaut Catherine (Cady) Coleman, Expedition 26 flight engineer, performs VO2max portable Pulmonary Function System (PFS) software calibrations and instrument check while using the Cycle Ergometer with Vibration Isolation System (CEVIS) in the Destiny laboratory of the International Space Station.
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