To examine the individual-level factors that predict energy intake (EI) after imposed exercise (EX) and sedentary time (SED) in children.Methods
Healthy-weight children ages 9–12 yr (n = 20) reported to the laboratory for one baseline and two experimental visits (EX and SED) each separated by 1 wk in a randomized crossover design. Percent body fat, weight (kg), and height (m) were used to calculate fat-mass index (FM index) and fat-free mass index (FFM index; kg·m−2). On the EX day, children exercised at 70% estimated V˙O2peak for 30 min on a cycle ergometer, whereas cardiovascular responses and RPE were measured. Objective EI (kcal) was measured at identical meals (breakfast, lunch, snack, and dinner) on the EX and SED days.Results
Total EI was not statistically different between the EX and SED days (t = 1.8, P = 0.09). FFM index was positively associated with EI on the EX day (r = 0.54, P < 0.05). RPE was also positively associated with EI on the EX day (r = 0.82, P < 0.001). Together, FFM index and RPE explained 77% of the variability in EX day EI (F(2,17) = 26.4, P < 0.001). For each unit increase in RPE, children consumed approximately 270 more calories on the EX day. A similar pattern of associations was observed on the SED day.Conclusions
FFM index was positively associated with EI on the EX day. Despite experiencing the same 70% relative exercise intensity, increased perceived difficulty predicted greater EI on both the EX and SED day. These findings demonstrate a role for both FFM and RPE in explaining EI variability in children.