title: Oxidation rate of exogenous carbohydrate during exercise is higher in boys than in men.
abstract: To determine whether the relative utilization of exogenous carbohydrate (CHO(exo)) differs between children and adults, substrate utilization during 60 min of cycling at 70% peak O(2) uptake was studied in 12 pre- and early pubertal boys (9.8 +/- 0.1 yr) and 10 men (22.1 +/- 0.5 yr) on two occasions. Subjects consumed either a placebo or a (13)C-enriched 6% CHO(exo) beverage (total volume per trial: 24 ml/kg). Substrate utilization was calculated for the final 30 min of exercise. During both trials, total fat oxidation was higher (5.4 +/- 0.5 vs. 3.0 +/- 0.4 mg x kg(-1) x min(-1), P < 0.001) and total CHO oxidation lower (27.4 +/- 1.5 vs. 34.8 +/- 1.2 mg x kg(-1) x min(-1), P < 0.001) in boys than in men, respectively. During the CHO(exo) trial, CHO(exo) oxidation was higher (P < 0.001) in boys (8.8 +/- 0.5 mg x kg(-1) x min(-1)) than in men (6.2 +/- 0.5 mg x kg(-1) x min(-1)) and provided a greater (P < 0.001) relative proportion of total energy in boys (21.8 +/- 1.4%) than in men (14.6 +/- 0.9%). These results suggest that, although endogenous CHO utilization during exercise is lower, the relative oxidation of ingested CHO is considerably higher in boys than in men. The greater reliance on CHO(exo) in boys may be important in preserving endogenous fuels and may be related to pubertal status.
authors.affiliation: Children's Exercise and Nutrition Centre, McMaster University, Hamilton L8N 3Z5, Canada M3J 1P3.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
authors.forename: Oded
authors.initials: O
authors.lastname: Bar-Or
authors.forename: Michael C
authors.initials: MC
authors.lastname: Riddell
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D000375:Aging / Q000502:physiology*; D001786:Blood Glucose / Q000032:analysis; D002648:Child; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange; D012119:Respiration; D016037:Single-Blind Method
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D019344:Lactic Acid