The effect of mode of exercise on fat oxidation during exercise

The purpose of this study was to determine the difference in the relative intensity for peak fat oxidation for cycle ergometer and treadmill exercise Twenty subjects (8 men and 12 women; age, 26.26 +/- 10.36 years; height, 171.18 +/- 8.22 cm;mass, 77.25 +/- 16.06 kg; percentage of body fat; 22.48 +/- 9.04) completed a maximal graded exercise test on a treadmill ((V)over dot O-2 peak = 41.36 +/- 14.49 ml.kg(-1).min(-1) as well as a cycle ergometer ((V)over dot O-2 peak = 36.45 +/- 13.59 49 ml.kg(-1).min(-1)). Subjects also completed submaximal exercise protocols on the cycle (3-minute stage, 30 W increments) and the treadmill (3-minute stage, 0.5 m.h(-1) increments). Recordings of (V)over dot O-2, respiratory exchange ratio (RER), ratings of perceived exertion, and heart rate were recorded and averaged over the last 30 seconds of each stage. Calculations of total caloric expenditure and fat oxidation were made using the Lusk table. Peak fat oxidation was identified as the stage with the greatest number of fat kilocalories expended (reliability = .60). Relative (V)over dpt O-2 at the intensity for peak fat oxidation was compared between exercise modes using dependent means t-tests. Significance was set at p < 0.05. Results showed no differences in the relative intensities for peak fat oxidation for treadmill exercise (40.72 +/- 14.07% (V)over dot O-2 peak) versus cycle exercise (40.94 +/- 9.60% (V)over dot O-2 peak). RER was significantly higher with the cycle (0.87 +/- 0.04) than with the treadmill (0.85 +/- 0.04); however, this did not result in any difference in total calories (treadmill = 6.52 +/- 3.70, cycle = 5.64 +/- 2.15, p = 0.36) or fat calories (treadmill = 3.23 +/- 1.54, cycle 2.36 +/- 1.31, p = 0.06) expended at peak fat oxidation. The absolute (V)over dot O-2 at peak fat utilization was 11% higher with treadmill exercise, but this mirrored differences in (V)over dot O-2 peak. We conclude that for both treadmill and cycle exercise, maximal fat calorie expenditure will occur around 40% of (V)over dot O-2 peak without significant differences in fat calorie expenditure.