Maximal Aerobic Capacity, VO2max, is one of eleven International Bedrest Standard Measures conducted on healthy subjects at the :envihab facility in Cologne, Germany. VO2max is directly related to the physical working capacity of an individual. An individual’s VO2max is affected by uptake of oxygen in the lungs, extraction of oxygen from the arterial circulation by working muscles and by cardiac output. Aerobic deconditioning causes a lowering of VO2max, which results in a diminished capacity to perform strenuous physical tasks. The purpose of the standard measures project is to populate a repository with data that enables high-level monitoring of countermeasure effectiveness and meaningful interpretation of health and performance outcomes. These standard measures will support future, hypothesis-driven research that enables planetary missions by providing an optimized minimal set of measures captured from subjects. These measures will be available to other studies under data sharing agreements as well as undergo analysis to understand risk posture.
Maximum aerobic capacity will be assessed using a graded exercise protocol on an electronically-braked cycle ergometer and a metabolic cart for gas exchange determination. For accurate collection of gases, subjects wear a nose clip and breathe through a respiratory valve. Small increments in workload are utilized in order to provide an individualized approach to achieve a subject's maximum aerobic capacity.
Subjects will warm up by cycling at a light workload of 0 to 75 revolutions per minute (rpm) for one to three minutes. During the test, subjects will maintain a pedaling cadence of 70 to 75 rpm. Workload begins at 50 Watts (W) for three minutes and is then increased by 25 W every minute. Increasing workload in small increments with each minute of exercise allows for optimal evaluation of ventilatory threshold and VO2max. Maximal exercise is achieved in approximately eight to 15 minutes. Testing is completed when 1) subjects are no longer able to maintain a pedaling rate of 70 rpm, 2) reach a plateau in oxygen uptake (VO2) despite further increases in workload, 3) achieve a heart rate greater than 90% of age predicted maximum accompanied by a respiratory exchange ratio greater than 1.10, or 4) indicate a desire to stop the test.
Heart rate will be monitored continuously during testing and blood pressure will be measured during each of the first three stages and every two minutes during the subsequent one-minute stages using a sphygmomanometer and stethoscope.
The scheduled days of collection are as follows:
The :envihab International Bedrest Standard Measures Test Battery is not a hypothesis-driven study, but rather a collection of data made available to future researchers and for trend analysis. As such, there are no specific hypotheses, outcome measures, or statistical analyses associated with the skeleton of the project. The questionnaire will capture a "snapshot" of optimized data that can be investigated by researchers in the future.
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