Graded exercise testing for spaceflight

We developed and validated a graded exercise protocol suitable for operational use on space station. The new treadmill protocol has three level-grade stages (3-min each) at 70, 80, and 90% of estimated VO2peak. The protocol maintains the third stage speed while grade increases each minute to produce work rates equivalent to 100, 107, and 115% of the estimated VO2peak. We compared the new protocol's peak and submaximal responses to those observed during a NASA graded exercise test. All mean protocol differences, including peak work rate (-1.8%), VO2peak (-6.4%), HRpeak (-2.4%), and VEpeak (-9.7%), were not significantly different from the expected measurement errors. We observed similar results for indices (the oxygen uptake at a HR of 150 and the HR's at 70, 80, and 90% of VO2peak) of the submaximal HR-VO2 relationship. The new protocol is an acceptable graded exercise test for periodic operational fitness tests.