The present study examined whether the reported lower values of anaerobic abilities in children and adolescents, both in absolute and related to bodyweight values, as compared to adults can be explained, partially at least, by a non-optimal testing apparatus. So, they cannot express their anaerobic abilities. Specifically, we examined the force-velocity (F-V) relationship on a mechanical cycle ergometer, in 23 adolescents and 11 adults, with two wheels of very different weights: 6.3 kg (Wh6) and 18 kg (Wh18). A higher wheel inertia might explain a late reach or no reach of the true peak velocity and the maximal anaerobic power (PmaxAn). The adolescent group showed higher Vo (V for zero braking force) values with Wh6 (238 +/- 14 vs 223 +/- 16 rpm) (P < 0.001) than with Wh18. The absolute or relative PmaxAn values for this group were slightly higher, but not significantly, with Wh6 (10.6 +/- 2.2 vs 10.2 +/- 1.9 W/kg). The delay to reach peak velocity was higher with Wh18 than with Wh6 (P < 0.001) in the two groups. In addition, the delay was always higher (P < 0.001) in the adolescent group compared to the adult group for both wheels. This suggests that the fatigue related to the observed late reach and the rapid decrease of power over time could lead to an underestimation of the PmaxAn peak in children.