Relative and absolute reliability of the crossover and maximum fat oxidation points during treadmill running

Abstract

Summary Objective was to investigate the relative and absolute reliability of cross over (COP) and maximal lipid oxidation (LIPOX max ) points during treadmill running in sedentary healthy subjects. Subjects and methods Twelve sedentary subjects (aged 20.5 ± 1.0 years) performed in random sequence two submaximal graded exercise tests to test the criterion standard for reliability of metabolic tests on treadmill over a time interval of four days. Maximal oxygen intake and maximal aerobic velocity (MAS) were assessed, using a progressive maximal exercise test on a treadmill (Cosmed T170, Germany). Subjects performed two submaximal graded exercise tests (T1 and T2), based on the measured maximal aerobic speed (MAS). Respiratory parameters, the COP and the LIPOX max points, and the maximal fat oxidation rate (MFO) were measured during these submaximal protocols. Results We found no significant differences between T1 and T2 with respect to COP, LIPOX max and the MFO. Intra-class correlation (ICC) measures of relative reliability were 0.91 for COP, 0.84 for LIPOX max and 0.803 for MFO. Coefficients of variation (CV) for COP and MFO values between T1 and T2 were low, falling well within the 10% criterion of absolute reliability (CV COP = 9.0%, CV MFO = 2.6%). However, LIPOX max showed greater variability (CV= 15.2%). The standard error of measurement ± minimal detectable change (SEM ± MDC) values were 0.89 ± 2.08 mL.min −1 .kg −1 , 1.79 ± 4.17 mL.min −1 .kg −1 and 23.74 ± 65.80 mg.min −1 for COP, LIPOX max and MFO, respectively. The mean differences (bias) ± 95% limits of agreement (LOA) were 0.4 ± 5.9 mL.min −1 .kg −1 , –0.4 ± 8.8 mL.min −1 .kg −1 and 10.3 ± 104.05 mg.min −1 for COP, LIPOX max and MFO, respectively. Conclusion Our data shows that COP, LIPOX max , and MFO measurements on a treadmill, over a time interval of four days, are reproducible. These metabolic measurements could be used in sedentary subject to calibrate training intensity.