Reproducibility of endurance capacity and V̇o2peak in male Sprague-Dawley rats

Abstract

The rat model of treadmill running is an invaluable tool for the investigation of experimentally and pathologically induced alterations in exercise performance. Interpretation of such data often presumes knowledge of the within-rat reproducibility of performance measures; however, the literature is bereft of this information. We tested the hypothesis that within-rat exercise endurance capacity and peak O2 uptake (V̇o2peak) are highly reproducible across five measurements spanning ∼5 wk when assessed with treadmill performance protocols. Male Sprague-Dawley rats ( n = 13) performed five graded exercise tolerance tests to fatigue and five maximal exercise tests on a motor-driven treadmill for determination of endurance capacity and V̇o2peak, respectively. There were no differences ( P = 0.47) in average time to fatigue among any of the five exercise tolerance tests (average range 45.9–52.1 min), and the average within-rat coefficient of variation (CV) over the five runs was 0.13. There were no differences ( P > 0.05) among the average CVs from any consecutive weekly exercise tolerance tests (range of 4 CVs 0.06–0.10). As expected with the increase in body mass, relative V̇o2peak decreased (average range from 80.1 to 75.7 ml·min−1·kg−1, P < 0.05) throughout the five maximal exercise tests. However, there were no differences ( P = 0.63) in the average within-rat CVs among any consecutive V̇o2peak tests (range of 4 CVs 0.03–0.04), and the average within-rat CV for all five tests was 0.06. The present data obtained from the protocols described herein demonstrate that within-rat measurements of endurance capacity and V̇o2peak are highly reproducible. These results have significant implications for improving and refining exercise testing and experimental designs.