A sub-group analysis was performed using a random effects model because of heterogeneity. The categorical variables of
the sub-group analysis were the program type, outcome, and mode. In the analysis of the program type, electrical
stimulation showed a larger ES (d = 1.174) than strengthening exercise (d = 1.105) and strength with aerobic exercise
(d = 1.043). The largest ES of electrical stimulation was interpreted with caution because it was based on two trials, and the
range of confidence interval was wide. The fact that the largest number of ESs (k = 107) appeared for strengthening exercises,
such as progressive resistant exercise, suggested that it was an accepted method for strengthening in individuals with CP.
Although the ES of this meta-analysis could not be compared because previous systematic reviews did not report the overall
ES, it is clear that strengthening interventions have benefit and large effect on individuals with CP.