Perceived exertion during exercise is associated with children's energy intake

Purpose: 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 VO_2peak 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.