Measurement Reproducibility Of Exercise Tolerance And Vo2peak In Male Sprague- Dawley Rats

Abstract

The rat model of exercise performance is an invaluable tool for the investigation of experimentally and pathologically induced alterations in exercise tolerance and VO2peak. Interpretation of such data often presumes knowledge of the within-rat reproducibility of these performance measures, however, the literature is bereft of this information. The development of reliable and reproducible measures of exercise performance in the rat would improve experimental design and strengthen confidence in data interpretation. PURPOSE: We tested the hypothesis that within-rat exercise tolerance and VO2peak are highly reproducible across 5 separate weekly measurements when assessed with specifically designed protocols. METHODS: On a custom motor-driven treadmill, 13 male Sprague-Dawley rats (initial age: 2-3 months, weight: 352 ± 13 g) performed 5 progressive endurance runs to fatigue for determination of exercise tolerance, and 5 maximal exercise tests for determination of VO2peak (ml/min/kg) via a metabolic chamber. The coefficient of variation (CV) was used to assess within-rat reproducibility. RESULTS: There were no differences (P = 0.47) in average time or distance run to fatigue among any of the 5 exercise tolerance tests, and the average within-rat CV for the 5 runs was 0.13 (avg. exercise tolerance range, 45.9 - 52.1 min). Additionally, there was no difference (P > 0.05) among the average CV from any two consecutive weekly exercise tolerance tests (CV range, 0.06-0.1). As expected with the increase in body mass, VO2peak decreased (P < 0.05) over the course of the 5 maximal exercise tests. However, there were no differences (P = 0.64) in the average within-rat CV among any of the consecutive VO2peak tests (CV range, 0.03-0.04) and the average within-rat CV for all 5 tests was 0.06 (avg. VO2peak range, 75.8 - 80.1 ml/min/kg). CONCLUSIONS: We have demonstrated that, using the protocols described herein, within-rat measurements of exercise tolerance and VO2peak are highly reproducible. The results of this study mandate the adoption of similar specific, reproducible protocols for use in the rat model of treadmill exercise performance and, therefore, have significant implications for improving and refining exercise testing and experimental designs. Support: Cytokinetics Inc., San Fransisco, CA and AHA 750090Z