The aims of this study were to: 1) study the cardiopulmonary responses during exhaustive isometric contraction in cerebral palsy (CP) children vs. apparently normal (AN) children 2) to study the relationship between muscle endurance and maximal O
$_{2}$
uptake (peak VO
$_{2}$
) in CP children. Eight CP children (GMFC 1 to 2) and 8 AN children underwent a graded cycle exercise test and a quadriceps force and endurance assessment with cardiopulmonary measurement on an isokinetic dynamometer. During isometric contraction, muscle endurance did not differ between the groups but a higher O
$_{2}$
uptake was shown in the CP group. Moreover in this group, peak VO
$_{2}$
was correlated with muscle strength (R = 0.77, P < 0.05) and endurance (R = 0.68, P< 0.05). Cerebral palsy children have a higher O
$_{2}$
uptake during isometric endurance testing despite a lower absolute isometric force but their quadriceps endurance is not impaired after normalization with muscle mass and time. Additionally, quadriceps strength and endurance in CP children were in relationship with their peak VO
$_{2}$
. This higher O
$_{2}$
uptake is probably due to coactivation and/or cocontraction during exhaustive quadriceps isometric contraction.
