Jessica Rose ^1,2* Christos Papadelis ^3,4

• ¹ Stanford University, Stanford, United States
• ² Stanford Medicine Children’s Health, Stanford, California, United States
• ³ Jane and John Justin Neurosciences Center, Cook Children's Health Care System, Fort Worth, Texas, United States
• ⁴ University of Texas at Arlington, Arlington, Virginia, United States

Spastic CP is characterized by four interrelated neuromuscular impairments, two that result from reduced descending neural activation: weak muscle and reduced muscle growth relative to skeletal growth resulting in short muscle and joint contracture; as well as two neuromuscular impairments that result from reduced neural inhibition: muscle spasticity characterized by increased sensitivity to stretch, and impaired selective motor control characterized by flexion and extension synergies that interfere with voluntary movements. (Zhou et al., 2017). Mirror movements also impact motor control and are thought to result from increased dependence on preserved motor pathways, (Hruby A et. al., 2023).While interventions for spastic CP often focus on tone, mobility is more often limited by weak and short muscle due to reduced neural activation and muscle growth. Further, short muscles, especially two-joint muscles, are particularly vulnerable to spasticity, the increased sensitivity to stretch as the muscle extends over both joints. Pain, illness, inflammation and anxiety can be misdiagnosed and treated as 'increased spasticity', especially in individuals who have limited mobility and limited communication, highlighting the need for improved health monitoring and exercise. Misunderstanding interrelations between neuromuscular impairments such as short muscle and muscle spasticity, leads to imprecise diagnosis, over treating muscle spasticity and under recognition of the impacts of sedentary life and reduced muscle growth on mobility. For children with spastic CP, muscle growth is inadequately monitored in the clinic and warrants focused clinical research. Current treatments for joint contracture, such as surgical tendon lengthening and skeletal realignment address musculoskeletal deformities that are years in the making, and therefore, have suboptimal outcomes. Early improved treatments for the underlying neuromuscular impairments of muscle weakness and reduced muscle growth could normalize musculoskeletal growth and prevent joint contracture and skeletal malalignment, minimizing the need for surgery. Muscle strength and length are highly responsive to stimuli (Greve KR et and therefore are promising targets for effective treatments. selective motor control also limits mobility and gait in predictable ways (Fowler et al., 2010, Clewes et al., 2024) and warrants further research and development of more effective interventions.This research article collection examines the impact of neuromuscular impairments on gait and mobility and highlights promising areas of interventions.In the study, "Children with bilateral cerebral palsy use their hip joint to complete a stepup task", investigators Vatsala Goyal, Keith E. Gordon and Theresa Sukal Moulton quantified differences in lower limb joint moment strategies of a step-up task, highlighting the impact of lower limb muscle weakness. They found differences in timing of lower limb joint moments during stance phase of a step-up task with increased dependence on the hip joint to keep the body upright and decreased use of the knee and ankle joints. The results identify the importance of hip extensor muscles in upright gait and posture and point to targeted methods of treatment to improve movement quality in bilateral CP."A new methodological approach to characterize selective motor control in children with cerebral palsy", by Valentina Graci, Mitchel O'neill, Meredith Bloss, Rahul Akkem, Athylia Paremski, Ozell Sanders and Laura Prosser, offers a new clinical assessment of motor control in CP. The research identifies obligatory muscle co-activation patterns and mirror movements that correlate with reduced gross motor function and point to areas for targeted treatment.The impacts on gait of the four neuromuscular impairments of spastic CP are described in "Neuromuscular impairments of cerebral palsy: contributions to gait abnormalities and implications for treatment", by Kylie M. Clewes, Claire Hammond, Yiwen Dong, Mary Meyer, Evan Lowe and Jessica Rose. The article includes an easy-to-use clinical form for video-based gait evaluation to identify impacts of neuromuscular impairments at key points during the gait cycle to better target treatment and improve gait abnormalities. Unilateral spastic Cerebral Palsy", by Elena Beani, Veronica Barzacchi, Elena Scaffei, Beatrice Ceragioli, Fabrizia Festante, Silvia Filogna, Giovanni Cioni, Simona Fiori and Giuseppina Sgandurra, demonstrates Oldrati, Verusca Gasparroni, Arianna Michelutti, Andrea Ciricugno, Renato Borgatti, Simona Orcesi, Elisa Fazzi, Morandi Alessandra, Jessica Galli, Luigi Piccinini, Maghini Cristina, Maria Arioli, Zaira Cattaneo, Cosimo Urgesi and Alessandra Finisguerra, describes current methods to evaluate a promising treatment to improve bimanual upper limb function. We hope that you enjoy this research article collection and gain context for developing effective evaluations of the etiology and neuromuscular impairments of spastic CP to better target treatment and improve mobility. We appreciate your interest and hope that you will be inspired to pursue these vital areas of research and development.