Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2003 March;43(1):36-43

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

Effects od submaximal intensity cycle ergometry for 1 hour on substrate utilisation in trained prepubertal boys versus trained adults

Foricher J. M., Ville N., Gratas-Delamarche A., Delamarche P.

Laboratory of Physiology and Biomechanics of Muscular Exercise University of Rennes 2-Haute Bretagne, Rennes cedex, France

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Aim. 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. Experi­mental ­design: sub­jects ped­alled for 1 ­hour on an ergoc­ycle at 40% or 60% of W. max (max­imal ­aerobic ­power). Par­tic­i­pants: 14 ­boys and 13 ­adults ­active in endu­rance ­sport (swim­ming). Meas­ures: pul­mo­nary res­pir­a­tory gas-­exchange ­ratio [RER = V.CO2/V.O2], ­used as the equiv­a­lent of the non pro­tein res­pir­a­tory quo­tient (RQ), was meas­ured at ­rest, at the 15th, 30th, 45th and 60th 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 (­EECHO) was ­lower in chil­dren com­pared to ­adults, ­even if the ­highest inten­sity ­involves a ­higher ­EECHO in ­both ­groups (p<0.05). ­Boys oxid­ised ­more ­lipid at 40% of W. max ­than 60% of W. max or ­adults at ­either inten­sity. CHO util­isa­tion was sig­nif­i­cantly ­increased at 60% vs 40% of W. max, yet ­lower in ­boys ­than in men (p<0.01). ­Lipids’ use, in g·min-1·kg-1FFM, was sig­nif­i­cantly ­higher in ­boys ­than in men at 40% of W. max (p<0.01).
Con­clu­sion. ­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.