Fig. 6

Hypothetical trajectory of muscle function (y axis) across the lifespan (age, x axis) in healthy TD individuals and individuals with CP, plotted for GMFCS level I, II, and III, an expansion of the concept proposed by Shortland [114]. Proposed trajectories transition from solid to dashed lines where literature is sparse. We do not present GMFCS IV-V—a reflection of the dearth of data from these cohorts. The dashed horizontal line represents the hypothetical threshold for functional self-sufficiency. Shaded blocks represent life stages to mark variations in growth rates: A) Infancy-early childhood: a period of rapid development, B) Childhood: a period of continued improvement, C) Adolescence: protracted improvement in TD with lesser gains in CP, D) Early-adulthood: reaching our peak, E) Adulthood: gradual decline F) Older age: rapid decline. Figure our own, created using Adobe Illustrator (Adobe, Inc., San Jose, CA, USA) under the University of Auckland site license