The effect of positive pressure treadmill training in young people with cerebral palsy

1. Name The effect of positive pressure treadmill training in young people with cerebral palsy. 2. Why: Any movement requires the coordination of multiple muscles at the same time. Advances in the techniques to analyse muscle patterns lead to the theories of modular control of the central nervous system—and the modules are called muscle synergies (MSs) (d'Avella et al., 2003). Children with Cerebral Palsy (CP) recruit fewer synergies during walking. Previously, we demonstrated the possibility to upregulate the number of MSs in a neurological population (Runnalls et al., 2019). This upregulation or higher number of MSs was achieved by providing body weight support (BWS). Moreover, similarly to our results, EMG activity is modulated using BWS (Colby et al., 1999). Since fewer or altered recruitment of MSs is proposed as the underlying mechanism of abnormal motor behaviour after neurological disorders (Cheung et al., 2009), overall, the effect of neural modulation of BWS over MSs could lead to new strategies for rehabilitation. Treadmill protocols have been shown to increase walking speed, endurance and improved gait kinematics (Provost et al., 2007) in children with different types and severity of CP (Chrysagis et al., 2012). Similarly, in CP populations, training with positive pressure treadmills has shown to be a significant improvement compared to regular physical therapy treatments for balance, force (Dadashi et al., 2018) and gait kinematics (Azizi et al., 2017). However, there is no agreement on protocols for gait training, and parameters depend on clinical principles and observations rather than objective parameters. Treadmill gait training is based on the principle of repetitive motor learning, promoting the formation of clustered dendritic spines in the motor cortex, which are necessary for long-lasting learning (Fu et al., 2012). Motor learning could be translated into acquiring new synergies (Berger et al., 2013) or improved temporal tuning (Dominici et al., 2011). Training with higher motor complexity could lead to better long-lasting motor outcomes. 3. What: Materials: Treadmill: We will use a positive pressure treadmill for gait training . Electromyography: Sixteen electromyography (EMG) sensors would be placed bilaterally on both legs. EMG data will be used to extract muscle synergies. Kinematics: 27 reflective markers will be used to calculate body kinematics during overground walking. Accelerometry: Seven accelerometers will be placed on the participant’s lower limb segments to calculate the lower kinematics. Design: The study consists of a randomized controlled trial, with an intervention of gait training under two different arms 1) high Body Weight Support (BWS) and 2) minimal BWS on a positive pressure treadmill, with a cross-over design where participants will switch protocols after two weeks from the end of the randomly allocated first training protocol. The participants will attend their participation in the Health & Rehabilitation Clinic of the University of Auckland. Two types of sessions during the study; two initial assessment sessions, at least eight training sessions and two post-training assessment sessions. The participants then will train by walking on an anti-gravity treadmill under the two study arms: A) low weight support and B) high weight support. Low support will consist of training with minimal weight support to aid the participants’ balance. The high weight support, as the intervention, will be adjusted individually for each participant based on the results of the treadmill assessment. More specifically, participants will train at the weight support level where they exhibit an increase in the number of synergies; this is expected to be around 50% of the participant’s own body weight. The weight support is provided by positive pressure through an inflatable bag. For both training modalities, participants will walk at their own self-selected speed and will be encouraged to increase it if possible at the beginning of every session. Each training protocol will last four weeks, 2-3 times a week (according to participant's availability) and one hour each session. Each visit is expected to last an average of 1-1.5 hours. Training will be done on a one-on-one basis, and session attendance will be recorded on RedCap. As a cross-over design, participants will have a wash-out period of two weeks between the trainings. All the procedures will be executed or under the supervision of physiotherapists and qualified research and clinical staff of the University of Auckland. To encourage participation and fidelity, participants will be reimbursed for their participation transport expenses.