BackgroundCerebral palsy is the most common brain injury in the pediatric population. Patients with cerebral palsy present different affectations such as decreased muscle strength, gait deviations, impaired proprioception, and spasticity. Isokinetic strengthening programs combined with intensive rehabilitation may improve muscle strength and therefore gait efficiency.ObjectiveThe primary aim of this randomized controlled trial is to compare the effect of an intensive rehabilitation combined with a nonfunctional isokinetic progressive strengthening program to an intensive rehabilitation alone on gait parameters and muscle strength in patients with cerebral palsy. Another goal of this study is to determine whether adding an isokinetic program to intensive rehabilitation is more effective than intensive rehabilitation alone at decreasing spasticity and improving joint position sense in patients with cerebral palsy.MethodsA total of 30 adolescents with spastic diplegia cerebral palsy (Gross Motor Function Classification System levels I to III) will be randomized, by an independent researcher, into a 3-week intensive rehabilitation and isokinetic progressive strengthening group or an intensive rehabilitation control group. Gait parameters, muscle strength, spasticity, and knee joint position sense will be assessed. These variables will be evaluated at baseline (T0) and at the end of the intervention (T1). The intensive rehabilitation will consist of physiotherapy sessions twice a day and hydrotherapy and virtual reality gait training once a day. The isokinetic training group will have a total of 9 supervised isokinetic strength training sessions focusing on knee flexors and extensors with different execution speeds.ResultsThe protocol has been accepted by the French National Ethics Committee in October 2022. The inclusion of patients will start in November 2022.ConclusionsThe combination of intensive rehabilitation with an isokinetic program on knee flexors and extensors has not been studied yet. The findings of this study may determine if an isokinetic strength training program of knee flexors and extensors is beneficial for the improvement of gait parameters, muscle strength, spasticity, and joint position sense in adolescents with spastic diplegia.International Registered Report Identifier (IRRID)PRR1-10.2196/43221