Static stretching in children with spastic cerebral palsy

Passive stretching is a commonly used treatment to combat cerebral palsy (CP), a common neuro- developmental disorder in children. Cerebral palsy refers to a group of disorders in the development of posture and motor control, occurring as a result of a non-progressive lesion of the developing central nervous system. CP is a lifelong condition that challenges the individual child, the family and the individual as an adult. Improving the ability to walk or perform other functional activities are often the primary therapeutic goals for children with CP. Changes in the musculoskeletal system such as shorter muscle fascicles and decreased muscle strength develop secondary and affect daily routines and therefore quality of life of the patients. Passive stretching is mainly used to combat muscle tightness caused by the upper-motor neuron syndrome and stretch hyperreflexia (i.e. spasticity). However, its effect on structural and neurological changes of the muscle and tendon remain unexplained. Although several animal studies have reported increasing muscle length because of an increase in number of sarcomeres, direct evidence of such effects in humans is rare. There are few studies that showed changes in muscle and tendon architecture in healthy individuals due to stretching. Consequently, it can be assumed that stretching may also cause changes in patients with CP. Due to an assumed reciprocal relation between stretch hyperreflexia and muscle tissue alterations, it can further be hypothesized that stretching might also have an impact on stretch hyperreflexia in children with CP, but this is yet only speculation. Therefore, the aim of this project is to gain a detailed understanding of the effects of acute and repeated passive muscle stretching on muscle and tendon morphology (e.g. lengths) and stretch hyperreflexia of the plantar flexors in children with spastic CP. In this study, novel methods will be used (three-dimensional ultrasound, motorized spasticity measurement) to test the stretching effects in children present with different spasticity levels and in different age groups. Furthermore, the effect of the intervention on gait will be assessed. Functional improvements (e.g. improved gait), positive changes in muscle and tendon properties and related reductions in stretch hyperreflexia are expected. The results of this project will create a better understanding of the effects of stretching in children with CP, and as a result, will have important clinical relevance. They additionally might change the treatment recommendations for children with CP based on scientific evidence. The project will lead to a better understanding of muscle properties and the influence of spasticity level as well as age on spastic muscle structure, which might give a new perspective and could influence or change the timing of different treatment modalities in children with CP.

Spastic cerebral palsy (SCP) is a common neuro-muscular disorder in children, resulting from a brain injury occurring early in infancy or before. The impairments of children with SCP, e.g., spasticity, muscle weakness, and poor motor control, cause gait abnormalities, joint deformations, and restrict their performance of daily activities. Besides, spastic muscles fail to grow along with the bones and show structural differences (e.g., increased fat content) that negatively affect the children's strength and functional capacity. All these changes highly restrict their participation in daily life and quality of life. Static stretching is an important component of the physical therapy of children with SCP. It is a non-invasive method used to increase muscle length, decrease muscle tightness, and to delay the onset of fixed muscle shortening. However, its effectiveness in patients with neuromuscular conditions was still in question. Proprioceptive neuromuscular facilitation (PNF) stretching is an alternative technique used in patients with spasticity and paresis aiming to positively affect spastic muscles and to improve muscle strength. However, the effects of PNF stretching had not been investigated in children with SCP. Therefore, the primary aim of this project was to gain knowledge about the acute (one-time application) and long-term effects (8-week application) of static and PNF stretching on the calf muscle properties in children with SCP. Furthermore, we examined the effects on ankle joint movement, calf muscle strength, reflexes, and gait function to receive a comprehensive picture. An initial session took place to familiarize the participants with the study. Examinations were then performed in three sessions, with the acute effects assessed in the first session. Up-to-date methods such as 2- and 3-dimensional ultrasound (muscle-tendon properties), an isokinetic dynamometer (muscle strength), and 3D motion capture system (gait analysis) were used. Although data analyses are still ongoing, we can already report that both stretching methods acutely increased joint motion. However, in contrast to our expectations, they had no effect on the muscle structure. Different to findings in healthy people, the whole calf muscle-tendon unit tended to elongate less after PNF stretching while it tended to elongate more after static stretching. This is likely due to a greater elongation of the related tendon after static stretching. Both stretching techniques led to the same long-term effects showing no meaningful changes in muscle properties, joint motion, and strength. These results indicate that spastic muscles may respond differently to acute and long-term stretching than healthy muscles. By showing that both stretching techniques do not lead to changes in muscle properties, that may counteract the pathological changes and improve muscle function on the long-term, we emphasize the need to develop and evaluate new conservative treatment/training strategies.