Mechanical and Morphological Changes of the Plantar Flexor Musculotendinous Unit in Children with Unilateral Cerebral Palsy Following 12 Weeks of Plyometric Exercise: A Randomized Controlled Trial

To investigate how plyometric exercise (PLYO-Ex) affects mechanics and morphometrics of the plantar flexor musculotendinous unit in children with unilateral cerebral palsy, 38 participants (aged 10–16 years) were allocated at random to either the PLYO-Ex group (n = 19; received 24 sessions of plyometric muscle loading, conducted 2 times a week for 3 months in succession) or the control group (n = 19; underwent traditional physical therapy for the same frequency and duration). Measurements were taken pre- and post-intervention. Standard ultrasound imaging was applied to evaluate morphometrics of the gastrocnemius muscle and Achilles tendon unit and an isokinetic dynamometer was used to evaluate maximum voluntary isometric plantar flexors contraction (IVC_max). With controlling for pre-treatment values, significant post-treatment changes favoring the PLYO-Ex group were observed for morphological (tendon (p = 0.003, η²_p = 0.23) length; belly length (p = 0.001, η²_p = 0.27); tendon thickness (p = 0.035, η²_p = 0.35); muscle thickness (p = 0.013, η²_p = 0.17); fascicle length (p = 0.009, η²_p = 0.18); pennation angle (p = 0.015, η²_p = 0.16)) and mechanical and material properties (IVC_max (p = 0.009, η²_p = 0.18); tendon’s elongation (p = 0.012, η²_p = 0.17), stiffness (p = 0.027, η²_p = 0.13); stress (p = 0.006, η²_p = 0.20); strain (p = 0.004, η²_p = 0.21)). In conclusion, plyometric exercise induces significant adaptations within the musculotendinous unit of the plantar flexors in children with unilateral cerebral palsy. These adaptations could improve muscular efficiency and consequently optimize physical/functional performance.