Crossover and maximal fat oxidation points during running and cycling in sedentary subjects

Objective: The purpose of this study was to compare crossover and maximal fat oxidation points during cycling and running in healthy participants. Methods: Maximal oxygen uptake VO2_max, maximal aerobic power (MAP) and maximal aerobic velocity (MAV) were assessed in 12 sedentary participants (aged 20.5±1.0 years), using a maximal progressive tests on a cycle ergometer and on a treadmill. Participants performed in random sequence, two submaximal graded exercise tests on a cycle ergometer (CE) and on a treadmill (TM), based on the measured MAP and MAV respectively. Respiratory parameters, the crossover (COP) and the maximal fat oxidation points (LIPOX_max) were measured during these submaximal protocols. Results: There were no significant mean (±SD) differences in COP (CE: 46.4±4.9%, TM: 47.4±3.7%; P=0.36) and in LIPOX_max (CE: 40.0±7.4%, TM: 40.2±2.1%; P=0.92) expressed in percentage of VO2_max between the two modes of exercise. The metabolic indices obtained on the CE and TM were significantly correlated (COP: r=0.85; P<0.0001 and LIPOX_max: r=0.79; P<0.002). Conclusion: Our data show that COP and LIPOX_max measured during submaximal exercise (based on measured MAP or MAV) were not affected by the choice of ergometer. Both CE and TM yielded accurate and quiet similar metabolic indices that could be used to individualize training in healthy sedentary adults.