Predictors of Treatment Response to Progressive Resistance Training for Adolescents with Cerebral Palsy.

Objective. The aim of the study was to examine the variability in plantar-flexor muscle strength changes after progressive resistance training for adolescents with cerebral palsy (CP) and to identify baseline variables associated with change in muscle strength. Methods. Thirty-three adolescents with CP were randomized to a 10-week progressive resistance training program as part of a randomized controlled trial (STAR trial). The associations between muscle strength at 10 weeks (n = 30 adolescents) and 22 weeks (n = 28 adolescents) and biomechanical and neuromuscular baseline characteristics, motor function, and fidelity to the program were examined with multivariable linear regression. Results. Changes in plantar-flexor muscle strength from baseline ranged from -47.7 to 192.3% at 10 weeks and -54.3 to 198.4% at 22 weeks. Muscle activation was the only variable associated with change in strength at 10 weeks and 22 weeks. A model containing peak muscle activity and baseline muscle strength explained 49.1% of the variation in change in muscle strength (R2 = 0.491) at 10 weeks and 49.2% of the variation in change muscle strength at 22 weeks (R2 = 0.492). Conclusion. Assessing levels of muscle activation may be able to identify responders to a progressive resistance training program for adolescents with CP. These findings are a first step toward developing tools that can inform decision making in the clinical setting. Impact. Due to the heterogenous nature of CP, it is challenging to assess the efficacy of strength training programs in individuals with CP and to understand the variability in outcomes among participants. This study provides a better understanding of the factors that predict response to an exercise program so that resistance training can be directed to those who will potentially benefit from it. Lay Summary. There is wide variability in how well young people with CP respond to resistance training. If you are a young person with CP, your physical therapist can measure the amount of your gastrocnemius muscle activity to get an indication of how well you will respond.