HRR and HRV findings suggest there are no differences in autonomic function during recovery from maximal exercise in lean and obese 8- to 12-year old children.

OMNI ratings of perceived exertion (RPE) and physiological responses in children (n=7 boys, 8 girls, 11.1±1.0 years) were examined during estimation (graded exercise test [GXT] and steady-state) and production (steady-state) trials on a cycle ergometer. Peak oxygen consumption (VOpeak) was determined via a GXT with RPE estimated every 30 s. Later, two 6-min trials were completed: Participants 1) estimated RPE at ~75% of VOpeak, 2) produced a level of exertion corresponding to their RPE at ~75% of VOpeak during the GXT. Data analysis included a one-way MANOVA and a paired t-test. The target intensity during the GXT corresponded to 74.2±2.5% of VOpeak; the steady-state estimation and production trials were performed at 76.5±2.7% and 68.5±14.1% of VOpeak, respectively (p>0.05). Mean RPE at ~75% of VOpeak during the GXT and production trial was 6.7±1.5; during the steady-state estimation trial RPE was 5.8±2.0 (p>0.05). There were no differences (p>0.05) in the physiological responses. Participants estimated RPE similarly at ~75% of VOpeak during both graded and steady-state exercise, but when asked to produce a given RPE, marked variability was observed in physiological responses. These findings may have implications in optimizing exercise prescriptions for children.

No abstract

Purpose: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. Methods: A total of 10 girls (10.4 [0.7] y) participated in the study. VO2peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO2peak and maximal sprints) before a 1-minute performance sprint. Results: The mean power, peak power, heart rate (HR), %HRpeak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HRpeak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). Conclusion: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

Purpose: This study examined metabolic flexibility with respect to fat metabolism during exercise in children who are lean (n=11; 10.9[0.9] y) and overweight/obese (OW/OB; n=9; 10.3[1.2] y). Method: Participants were grouped based on body mass index percentiles for age and sex. Groups were mixed in age and sex. Participants completed two 20-minute exercise bouts on a cycle ergometer, separated by a 10-minute rest. Bout 1 consisted of 10 minutes at 50% VO2peak and 10 minutes at 75% VO2peak. Bout 2 was 20 minutes at 50% VO2peak. Absolute fat oxidation rate (FOR), FOR relative to body mass, FOR relative to fat-free mass, and proportional fat use were measured at 10 minutes of bout 1 and 5, 10, 15, and 20 minutes of bout 2. Results: Absolute FOR was higher in the OW/OB group (range: 117.8 [55.1]–206.2 [48.3] mg·min−1) than in the lean group (81.1 [32.2]–152.2 [38.2] mg·min−1); however, there were no significant main effects for group or significant interactions for proportional fat use, FOR relative to body mass, or FOR relative to fat-free mass. Conclusion: Children in this age range who are overweight/obese do not display impaired metabolic flexibility with respect to fat metabolism during exercise.