Exercises implementing resistance (load) against muscle work with no increases in resistance during the course of the exercise program have been reported as muscle strengthening [1,2]. However, others support that muscle strengthening exercises to increase muscle force production need gradual increases in resistance applied . Thus, the term “Progressive Resistance Exercise” (PRE) has emerged , that implies that a program should be progressed over time to increase volumes with heavier resistance (loads) for large muscle groups, to maximize gains in muscle strength . As no previous systematic review has specifically addressed the effects of PRE on people with cerebral palsy, the recent systematic review of randomized controlled trials of Bania et al., has examined the effects of PRE programs in these people. This review was conducted with rigor and designed to have a low risk of bias in the results (including evaluation of evidence of each meta-analysis based on pre-determined GRADE criteria), although the number of trials included may be small and most trials had small samples.
The results of this review supported the effects of PRE on the strength of the lower limb extensor muscles. This increase in muscle strength following PRE appeared to be maintained for at least 11 weeks after PRE stops. This review finding is important as it appears that muscle strength actually can be increased by such programs and with no adverse events. Other review results demonstrated that the PRE effect on gross motor function and participation of people with cerebral palsy approached but did not reach statistical significance. Thus, these results raise important questions about the best way to make PRE work for other outcomes too, including considerations about factors such as practice of more activity or addressing social interaction along with PRE.
This review was the first that performed a meta-regression to determine which PRE parameters provided the most beneficial effects, and no association was observed between the PRE intensity or duration and effects on muscle strength. Lack of variation in training intensity between trials resulted in no association, and, therefore, more trials with a variety of intensity could probably provide more clear findings.
Further, for decades, it was believed that interventions of resistance training in people with CP should be avoided because such interventions would increase spasticity. This hypothesis, has been rejected since the 80s, and our review adds to existing literature supporting that implementing muscle resistance programs in people with cerebral palsy does not result in any increases in spasticity.