Is there a relationship between muscle-tendon properties and a variety of functional tasks in children with spastic cerebral palsy?

Background: Cerebral palsy (CP) is the most common motor and movement disability in childhood. The mechanomorphological alterations of the spastic muscle itself as well as the functional limitations in CP are well documented. However, the relationship between muscle tendon properties and functional tests in CP remains unknown. Research question: The aim of this study was to explore the relationship between spastic muscle mechanomorphological properties and functional performance in children with CP. Methods: This study included retrospective data from 22 children with spastic cerebral palsy with a mean age of 12.8 years (19 GMFCS I/3 GMFC II, 15 male/7 female, 8 unilateral involved/14 bilateral). Mechanomorphological properties of gastrocnemius (GM) and Achilles tendon (AT) were correlated with a variety of functional measures, maximal isometric strength, the Muscle Power Sprint test (MPST), 6-minute walk test (6MWT) and 3D-gait analysis using the Pearson Coefficient. Results: Muscle-tendon properties were normalized to remove anthropometric dimensions because of strong associations with anthropometric data. Higher isometric muscle strength was related to longer normalized GM fascicle lengths (r = 0.67, p < 0.01). The distance reached in the 6MWT positively correlated with normalized GM fascicle lengths (r = 0.61, p < 0.01). Higher AT stiffness was associated with faster performance in the MPST (r = 0.77, p < 0.01). Finally, there was an association between ankle power and both longer normalized AT length and shorter muscle belly (r = 0.60 and r = 0.54, p < 0.01). Significance: The findings of this study give more insight into the function specific adaptations of a spastic muscletendon unit. While walking, assessed through the 6MWT, was related to normalized gastrocnemius fascicle length, sprint performance was associated with an increased AT stiffness. These results provide a better understanding of the relationship between functional tasks and spastic muscle-tendon properties, which offers potential for improved and targeted interventions in CP.