The present study was undertaken in order to evaluate the effect of an aerobic training programme on the maximal power (Pmax) developed during a short-term exercise test in prepubertal children. Thirty-three 10-11 year old boys and girls were investigated: 17 (TG) participated twice a week (1 h per session) in a 13-week running programme and 16 (CG) served as a control group. Pmax was measured during a force-velocity test conducted on a friction-loaded cycle ergometer. The force (Fopt) and velocity (Vopt) at which Pmax was obtained were determined. Lower limb muscle mass (LMM) was evaluated by means of dual X-ray absorptiometry. Following training, Pmax increased even when muscle mass change due to the growth process was taken into account (Pmax W: + 23 %, W x kg(-1) LMM: + 18%, p < 0.001). The increase in Fopt was principally responsible for such an improvement since no alteration was noticed for Vopt after training. As for Pmax, Fopt was still greater following training when LMM was taken into account (p < 0.01). Furthermore, no changes were noticed for CG for all variables evaluated during the anaerobic test after the study period. Differences between TG and CG regarding Pmax and Fopt were obtained after training only. In conclusion this study highlights the effectiveness of an aerobic training programme to improve the maximal power during short-term exercise in prepubertal children.