Reliability of Time to Exhaustion Treadmill Running as a Measure of Human Endurance Capacity

Little if any research has examined the variability in time to exhaustion (TTE) during submaximal treadmill running. This study investigated the test-retest reliability of submaximal treadmill TTE as a measure of endurance capacity. 16 endurance-trained males (n=14) and females (n=2) completed a run to exhaustion at 70% V.O-2max (T1) and repeated the same run 3 weeks later (T2). At 30-min intervals during each run, expired gas, heart rate (HR) and ratings of perceived exertion (RPE) were collected. Mean +/- SD TTE was 96 +/- 20min in T1 vs. 101 +/- 29min in T2 (P=0.3). The mean +/- 95% confidence intervals (CI) of the coefficient of variance (CV) was 5.4% (1.4-9.6). The average intraclass correlation coefficient (+/- 95% CI) was 0.88 (0.67-0.96) between trials. The respiratory-exchange ratio was not different between trials, T1: 0.87 +/- 0.1 and T2: 0.89 +/- 0.1 (P>0.05) and neither was total whole-body carbohydrate oxidation (2.1 +/- 0.4gmin(-1) and 2.3 +/- 0.6gmin(-1)), fat oxidation (0.6 +/- 0.2gmin(-1)), HR (178 +/- 8 and 175 +/- 7beatsmin(-1)) or RPE (17 +/- 3 and 16 +/- 3). These results suggest that use of prolonged treadmill-based TTE can be a reliable research tool to assess human endurance capacity in aerobically-trained men and women.