The effects of stage duration on achieving a plateau in oxygen uptake during a maximal exercise test

This investigation examined whether the length of stage during a GXT could influence the occurrence of a plateau in V02. Ten males between the ages of 18 and 45 volunteered to participate in the study. They each completed a Physical Activity Readiness Questionnaire and an informed consent form. Each participant completed four graded exercise tests to exhaustion on the treadmill. The first test was used to obtain the subject's maximal heart rate, so the speed of the treadmill for the three subsequent tests could be set at 80% of their maximal heart rate. All tests were performed within a two-week period for each subject with no tests performed on consecutive days. During the tests the subjects ran on the treadmill at a constant speed while the grade of the treadmill was increased every 30, 60, or 90 seconds depending on the protocol. While running on the treadmill expired air was analyzed using an automated metabolic system. Upon completion of each test a small blood sample was obtained and used to determine post-exercise lactate concentration. The analysis of variance showed significant differences between grade at exhaustion and time to exhaustion between all three protocols. A significant difference in RER and postexercise lactate was observed between the 30 and 60-second protocols and the 30 and 90-second protocols, (p < .001) and (p < .05) respectively, with no differences between the 60 and the 90-second protocols. Additionally, no significant differences were found for VOimax, or plateau attainment when the three treatments were compared. The data show that shorter duration GXT's will elicit higher RER values and higher post-exercise lactate values.