A Comparison of a Speed vs. Grade Incremental Treadmill Protocol on Maximal Oxygen Consumption and Anaerobic Threshold in Division II Cross-Country Runners

Abstract

PURPOSE: To compare oxygen consumption and anaerobic threshold during a speed incremental treadmill protocol (S) vs. a grade incremental treadmill protocol (G) with equivalent metabolic increments. METHODS: Thirteen subjects (age= 21.7 ± 3 yrs, ht = 172.3 ± 6 cm, bm = 64 ± 6.2 kg) performed two different running protocols in a randomized design with a minimum of 5 days rest between trials. Each stage was 3 minutes long. Trial G was held at a constant speed that coincided with 60–70% of the individual's maximal heart rate reserve while the incline was increased 2% each stage. The S trial began at the matched speed and increased speed equivalent to the predicted metabolic cost of each grade increase from trial G. Metabolic data was obtained using open-circuit spirometry. HR was obtained by telemetry, and finger stick lactate samples were obtained 3-minutes post. Predicted oxygen consumption was derived from the metabolic equations in the ACSM Guidelines (GETP7). RESULTS: Statistical analysis by paired t-test and Pearson correlation were applied to these data at the .05 level of significance. No significant differences were found in predicted VO2 between protocols at any stage. The ACSM equations over-predicted the metabolic demand during every stage of each test (p < .05). No significant difference was found in HRmax or VO2max between protocols. Trial G had a shorter total treadmill time than trial S (13:47 ± 1:28 min:sec vs. 15:06 ± 1:37) and elicited a higher lactate response (10.0 ± 2 mmol in trial G vs. 8.6 ± 1.7 mmol in trial S) (p < .05). CONCLUSION: The ACSM prediction equations significantly over-estimate the actual oxygen consumption by 8.9%. While a grade incremental protocol may provide a more time-efficient test for cross-country runners, a speed protocol readily translates to training workloads. Equivalent results may be obtained in terms of maximal oxygen consumption, anaerobic threshold, and max heart rate using either a speed- or grade-driven protocol.