Age-Related Differences in Muscle Size and Strength between Individuals with Cerebral Palsy and Individuals with Typical Development.

AIM: Examine age-related differences in muscle size and strength of the knee extensors in individuals with cerebral palsy (CP) and individuals with typical development (TD).

METHODS: 54 individuals with CP (14.5 ± 4.5 years, GMFCS I-V) and 33 individuals with TD (16.2 ± 5.5 years) were included. Relationships between rectus femoris (RF) and vastus lateralis (VL) muscle volume and isokinetic knee extensor strength with age were examined with linear regression and ANCOVA to test age-related differences between groups.

RESULTS: Linear regression for muscle volume with age was statistically significant in TD (VL: r 2  = 0.48, RF: r 2  = 0.56, p  < .05) and those with CP (VL: r  = 0.36, RF: r 2  = 0.27, p  < .05) with no differences in regression slopes between groups ( p  > .05). Age-related strength differences were observed in TD ( r 2  = 0.66, p  < .001) and those with CP ( r 2  = 0.096, p  = .024), but the slopes were significantly different between CP and TD ( p  < .001).

CONCLUSION: Age-related linear differences in muscle volume and strength were observed in both groups. The linear slope of the age-related differences in knee extensor muscle strength and strength-to-body mass ratio were significantly lower in individuals with CP compared to individuals with TD, suggesting that strength is insufficient to keep up with gains in body mass during growth.