Comparison of fat oxidation over a range of intensities during treadmill and cycling exercise in children

Substrate metabolism differs between children and adults and is important for weight management during childhood. A direct comparison of fat oxidation over a range of exercise intensities and the estimation of Fatmax (exercise intensity that elicits maximal fat oxidation (MFO)) during treadmill (TM) and cycling exercise (CE) does not appear to be available in children. Fat oxidation and Fatmax were compared during TM and CE in 22 pre- to early pubertal children (9 girls and 13 boys). Fat oxidation was higher for TM compared with CE over a range of absolute and relative exercise intensities and this difference was more pronounced at higher intensities (P ≤ 0.05). Fat oxidation was higher in boys compared with girls at similar relative, but not absolute intensities (P ≤ 0.05). Fatmax was higher during TM compared with CE and higher in boys compared with girls (P ≤ 0.05). The 5% Fatmax zone (range of exercise intensities where fat oxidation was within 5% of MFO) spanned a wider range of intensities for TM compared with CE (P ≤ 0.05). Collectively, these findings suggest that exercise programmes aimed at promoting high rates of fat oxidation in pre- to early pubertal children should include TM rather than CE regardless of exercise intensity. Furthermore, Fatmax values indicate that brisk walking or slow running promotes MFO rates in this population.