Previous studies of short term power output in young people and adults have used cycle ergometers that cannot control cadence or inertial resistance. An innovative isokinetic ergometer has now been designed and the purpose of this study was to investigate the isokinetic short term power output of twelve 15-year-old adolescent girls and nine 21-year-old female adults. Short term power was measured by a power-cadence test and included the calculation of the optimised peak power (PP
$_{opt}$
) and optimal cadence (C
$_{opt}$
) at PP
$_{opt}$
. Each subject completed seven maximal sprints, starting at an initial pedal cadence of 90 rev·min
$^{-1}$
which after each subsequent five minute rest period, was increased by 10 rev·min
$^{-1}$
. Significant differences in absolute PP
$_{opt}$
were found between adolescent (624± 985 W) and adult females (740 ± 157 W) respectively (P < 0.05). Significant differences were found in short term power standardised according to leg volume (45.4± 10.8 and 25.8 ± 2.1 W·L
$^{-1}$
) between female adolescents and adults but not according to body mass (P > 0.05). The C
$_{opt}$
at PP
$_{opt}$
for adolescent females (116 ± 6 rev·min
$^{-1}$
) was not significantly different to adult females (118 ± 13 rev·min
$^{-1}$
). These results add to the scarce amount of isokinetic data on females and provide evidence that age differences in power are not due to cadence dependent factors.
