This study examined the performances of children exercising against varying braking forces in short-term, all-out cycling tests. The braking force resistances were 0.04, 0.065, 0.075, and 0.08 kiloponds for every kilogram of body mass (kp.kgBM-1). Results for the peak and mean power performances in 30 s Wingate Anaerobic Tests (WAnT) were recorded for a wide age range of male and female children [6 (n = 23), 8 (n = 19), 10 (n = 19), and 12 (n = 14) years of age]. Univariate ANOVAs with repeated measures on resistance, and Newman Keuls post hoc analysis tests revealed that the absolute peak and mean power responses of the children increased incrementally with age and demonstrated very few sex differences. The overall meaned peak and mean power values of the four resistances and age groups were 161, 231, 242 and 248 Watts and 130, 183, 189, and 196 Watts, respectively. In all of the age groups the three higher resistances (0.065, 0.075, and 0.08 kp.kgBM-1) produced significantly higher peak and mean power performances than did the 0.04 kp.kgBM-1 resistance. The overall meaned relative peak and mean power values of the four resistances and age groups were 4.9, 6.9, 7.4 and 7.4 W.kg-1 and 4.2, 5.2, 5.7 and 6.2 W.kg-1, respectively. Among the three higher resistances there was no one resistance which elicited a significantly more powerful performance.