Evaluation of Maximal Oxygen Uptake and Submaximal Estimates of VO2max Before, During, and After Long Duration International Space Station Missions (VO2max) - 02.22.17
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. Science Results for Everyone
VO2max, or aerobic capacity, indicates how much physical exertion someone can sustain. In space, the ability to perform space walks and responding effectively to emergencies requires astronauts to be very fit . Researchers found that aerobic capacity in space is related to the intensity of exercise. Those exercising at normal intensity saw initial decrease followed by a gradual increase over time. Maximum intensity exercise appears better at improving aerobic capacity. Aerobic capacity returned to preflight levels one month after landing, indicating no long-lasting effects on lungs and muscles. Testing both intensities provides a more comprehensive picture, and better documentation of intensity and specific regimens is needed. Experiment Details
Alan D. Moore Jr., Ph.D., Houston, TX, United States
Simon N. Evetts, Ph.D., European Astronaut Centre, Cologne, Germany
Frank A. McCleary, Lockheed Martin, Houston, TX, United States
Alan H. Feiveson, Ph.D., Johnson Space Center, Houston, TX, United States
Stuart M. C. Lee, Ph.D., KBRwyle, Houston, TX, United States
European Space Agency (ESA), Noordwijk, Netherlands
NASA 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
April 2009 - March 2013
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.
Operational Requirements and Protocols
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.
Decadal Survey Recommendations
Animal and Human Biology AH9
Current and future space exploration activities requires astronauts to have excellent aerobic capacity (maximum work a person can do as measured by oxygen consumption - VO2). International Space Station (ISS) crew members exercise with treadmill, cycle, and resistance exercise device daily to maintain bone, cardiovascular, and musculoskeletal health during spaceflight; however, the effectiveness of these exercises to preserve aerobic fitness is not yet known because maximum aerobic capacity (VO2peak) during and after ISS missions has not been measured. Data collected during normal intensity exercise before, during, and after prolonged ISS flights showed: 1) Heart rate (HR) response to exercise is increased and oxygen uptake is lowered early after flight indicating decreased aerobic capacity during this time, but both quantities return to preflight levels after a month; 2) HR response to exercise appears increased early during flight, however, as mission duration progresses aerobic capacity increases; and 3) although gender was associated with differences in the aerobic capacity before, during, and after flight, there was no gender/time interaction, thus male and female astronauts did not appear different in their respective responses to prolonged spaceflight. For maximal exercise testing, results showed for most participants the average VO2peak and peak power were substantially decreased at the first in-flight test (about day 15) by 17% and 24% respectively. After 15 days, VO2peak and peak power showed modest upward trends during flight. On Return plus 1 day and plus 10 days, mean VO2peak and peak power values were significantly lower than preflight, but had recovered fully by one month after landing. A small group (4) was able to maintained their VO2 peak from preflight to postflight. This sub-group maintained their VO2 peak exercised on the cycle at a higher percentage of peak HR (about 10% higher) and spent a greater percentage of their time exercising above 70% of peak HR compared to those who experienced a decrease in VO2peak. It is possible that the aerobic capacities of some crew members are maintained or recovered fairly well during flight, but the relative decrease in volume of blood plasma that exists due to microgravity exposure obscures this upon return to Earth. Data also shown that the decrease in maximal oxygen uptake (VO2max) that accompanies time in microgravity reflects decreases in both convective (bulk movement of oxygen in air or blood based on levels of activity) and diffusive (movement through cell membranes) oxygen transport. So far, no long lasting effects on aerobic capacity from the missions were found, but results have practical implications for future long-duration space missions and highlight the need to resolve the specific mechanisms underlying these spaceflight-induced changes along the O2 transport pathway. Both moderate and peak exercise testing help to give a more comprehensive picture of cardiovascular conditioning in microgravity. More definitive research should be conducted regarding the adaptations to flight, including better documentation of the intensities of exercises performed and evaluations of specific exercise regimens.^ back to top
Moore Jr. AD, Everett M, 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. DOI: 10.1152/japplphysiol.01251.2013.
Ade CJ, Broxterman RM, Moore Jr. AD, Barstow TJ. Decreases in maximal oxygen uptake following long-duration spaceflight: Role of convective and diffusive O2 transport mechanisms. Journal of Applied Physiology. 2017 February 2; epub. DOI: 10.1152/japplphysiol.00280.2016. PMID: 28153941.
Hoffmann U, Moore Jr. AD, Koschate J, Drescher U. VO2 and HR kinetics before and after International Space Station missions. European Journal of Applied Physiology. 2015 December 10; epub. DOI: 10.1007/s00421-015-3298-2. PMID: 26662601.
Moore Jr. AD, Lynn PA, Feiveson AH. The first 10 years of aerobic exercise responses to long-duration ISS flights. Aerospace Medicine and Human Performance. 2015 December 1; 86(12): 78-86. DOI: 10.3357/AMHP.EC10.2015.
Ground Based Results Publications
Lee SM, 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.
Hoffmann U, Moore Jr. AD, Koschate J, Drescher U. Influence of weightlessness on aerobic capacity, cardiac output and oxygen uptake kinetics. Exercise in Space: A Holistic Approach for the Benefit of Human Health on Earth; 2016.
Lee SM, 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, 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.
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.
+ View Larger Image
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.
+ View Larger Image
NASA Image: ISS030E022589 - View of Dan Burbank exercising on the Cycle Ergometer with Vibration Isolation and Stabilization (CEVIS) during a session of VO2max.
+ View Larger Image
NASA Image: ISS032E016875 - NASA astronaut Sunita Williams performs a VO2max experiment while using the Cycle Ergometer with Vibration Isolation System (CEVIS).
+ View Larger Image
NASA Image: ISS038E009210 - JAXA astronaut Koichi Wakata, Expedition 38 flight engineer, performs a VO2max session.
+ View Larger Image