Children with cerebral palsy (CP) are weaker and have smaller muscles than children without CP. Early research in this area showed that children with CP can gain strength with resistance training without increasing spasticity (a long-held myth). We know that their muscles gain volume with strength training. Children with CP appear to benefit from the same exercise training principles as children or adults without CP, such as specificity of training, adaptation, overload, progression, and individualized training programs. Researchers in the subject area have been divided in recent years as to the benefits of strength training for children with CP.[3-6] Some previous studies have found improvements in gait as a by-product of strength training. These studies included children with hemiplegia as well as diplegia and, mostly, children who were classified at Gross Motor Function Classification System (GMFCS) levels I or II.[4-6]
As our methods of measurement and research design have become more sophisticated, we are increasingly able to measure improvements in strength and function in a variety of ways. Important questions at this time are (1) Is strength a critical component for improved or maintained functional walking in children with cerebral palsy? (2) If so, how is strength for walking best trained and maintained in this population? (3) What are the important training strategies for functional walking at different ages? Speed? Endurance? Variability? What happens if we train these but not strength?
The paper by Taylor et al. is interesting and at the same time disappointing. It is well designed with blinded assessors, intent-to-treat analysis, and had only one drop-out in each group. The power analysis indicated that 31 participants would be required in each group but only 23 and 24 completed the study. The groups were fairly equivalent and included children with diplegia at GMFCS levels II and III. The children trained in local gyms using standard protocols for progressive resistance training.
Children who trained for strength twice weekly for 12 weeks got significantly stronger in the specifically trained muscles but not in opposing muscles (leg press –trained vs reverse leg press-not trained). Mobility testing in the 6-minute walk test, stairs timed test, gait kinematics, and GMFM dimensions D (standing) and E (walking, running, and jumping) did not change.
Taylor et al. have demonstrated that resistance training improves strength, as have many other authors. This study adds to the literature with a good design and quality indicators; however, it is limited because it does not inform us on how to improve or maintain functional gait or understand how strength is or is not related to gait. Because gait was not trained, at this point in the state of the literature (considering basic exercise science principles), it seems disingenuous to expect that it would change in spite of earlier articles to the contrary. The authors offer hypotheses for the divergence of results. Therapists who look to evidence in the literature to design their interventions will not find this article useful.
The use of fundamental principles of exercise training and testing should be paramount in establishing the basic question of any research project.