Determination of Initial Intensity to Elicit Proper Test Duration for a Modified-Astrand Protocol

Abstract

The modified-Astrand protocol is used often in research when measuring VO2max, particularly in trained runners. The starting speed of the protocol is subjectively chosen by the researcher and varies based on training and racing history of the subject or subject population. This process results in test durations that may or may not meet the 10 minute test end point recommendation. There is currently no recommendation of an objective intensity for beginning the modified-Astrand protocol to achieve a proper test duration of 10 minutes in well-trained runners. PURPOSE: To determine an objective intensity for beginning the modified-Astrand protocol in an effort to elicit a test duration of 10 minutes. METHODS: Thirteen well-trained runners and triathletes (mean VO2max = 64.9ml·kg-1·min-1) underwent an incremental treadmill test to exhaustion utilizing the modified-Astrand protocol. VO2 was averaged every 30 seconds throughout testing. VO2max was confirmed using a verification phase protocol. Correlations were determined between test duration and both steady state VO2 during the first stage (as a percentage of VO2max, SSVO2) and steady state heart rate during the first stage (as percentage of maximal heart rate, SSHR). Bivariate regression was used to predict test duration from SSVO2 and SSHR. RESULTS: All subjects achieved VO2max based on results of the verification phase test. SSVO2 was significantly related to the duration of the test (r = -.837, p < .001, r2 = .700). SSHR was also significantly related to the duration of the test (r = -.791, p = .001, r2 = .626). Bivariate regression resulted in the determination that an initial work rate eliciting 65% of VO2max or 83% of maximal heart rate will likely result in a test duration of 10 minutes (SSVO2 SEE = .937 min, SSHR SEE = 1.27 min). CONCLUSIONS: It is suggested that an initial workrate of 65% VO2max or 83% of maximal heart rate is chosen when using the modified-Astrand protocol with well-trained runners in order to attain the recommended test duration of 10 minutes. Supported by The Ohio State University Alumni Grant for Graduate Research and Scholarship