Effects of submaximal intensity cycle ergometry for one hour on substrate utilisation in trained prepubertal boys versus trained adults.
OBJECTIVE
Substrate utilisation during exercise might be different in trained prepubertal boys compared to trained adults, so dietary advice usually given to endurance trained adults may need to be adapted for endurance trained children.


METHODS



METHODS
subjects pedalled for 1 hour on an ergocycle at 40% or 60% of Wmax (maximal aerobic power).


METHODS
14 boys and 13 adults active in endurance sport (swimming).


METHODS
pulmonary respiratory gas-exchange ratio [RER = VCO(2)/VO(2)], used as the equivalent of the non protein respiratory quotient (RQ), was measured at rest, at the 15(th), 30(th), 45(thv and 60(th) min of exercise in order to calculate energy expenditure.


RESULTS
Relative resting energy expenditure was significantly higher in boys than in adults. During exercise, energy expenditure (EE) was significantly lower in children than in adults (p<0.001), whereas fat-free mass relative EE was only influenced by intensity. Relative EE from carbohydrates (EE(CHO)) was lower in children compared to adults, even if the highest intensity involves a higher EE(CHO) in both groups (p<0.05). Boys oxidised more lipid at 40% of Wmax than 60% of Wmax or adults at either intensity. CHO utilisation was significantly increased at 60% vs 40% of Wmax, yet lower in boys than in men (p<0.01). Lipids' use, in g x min(-1) x kg-1)FFM, was significantly higher in boys than in men at 40% of Wmax (p<0.01).


CONCLUSIONS
Trained children, at rest, had greater fat-free mass energy expenditure than adults, which may be linked to growth processes that remain unclear. During exercise, in boys, the main observation was the increase in CHO dependence relative with the intensity. Thus, it appears that CHO feeding is as important in endurance-trained boys as in endurance-trained adults, especially when exercise intensity approaches that of competition or training sessions.
Foricher
J M
JM
Laboratory of Physiology and Biomechanics of Muscular Exercise, University of Rennes 2-Haute Bretagne, Rennes cedex, France. jeanmarc.foricher@free.fr
Ville
N
N
Gratas-Delamarche
A
A
Delamarche
P
P
D000328:Adult; D050260:Carbohydrate Metabolism; D002648:Child; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D050356:Lipid Metabolism; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D010806:Physical Education and Training / Q000379:methods; D011659:Pulmonary Gas Exchange / Q000502:physiology; D015219:Substrate Cycling / Q000502:physiology; D013995:Time
D019344:Lactic Acid