The goal of this clinical trial is to help understand spinal cord excitability in children with cerebral palsy compared to neurologically typical children. The main questions it aims to answer are:

• What are the mechanisms of spinal circuit hyperexcitability in CP?
• Can transcutaneous spinal cord stimulation reduce spinal circuit hyperexcitability?

Participants with cerebral palsy will be asked to complete:

• Movement and strength exercises
• Mild, non-invasive stimulation on the back and legs that feels like a light tap.
• Gentle, non-invasive tests that help us see how the brain and the spinal cord communicate with the muscles

This is a clinical trial designed to evaluate spinal circuit hyperexcitability in children with cerebral palsy (CP) and to explore the potential of transcutaneous spinal cord stimulation (tSCS) to reduce excitability and improve spasticity. The investigators will also examine the mechanisms underlying this potential reduction of spinal hyperexcitability.

The investigators will non-invasively record a range of electrophysiological responses using surface electrodes while participants perform isometric tasks. These recordings will help to better understand the differences in spinal excitability between children with CP and typically developing peers and will provide early insight into how tSCS might modulate these responses.

This study has two aims: The first aim is to evaluate spinal circuit excitability in Children with CP and in children without neurological conditions (controls). Several electrophysiological markers will be collected, including sensory reflex responses, reciprocal inhibition, motoneuron firing patterns, and motor evoked potential by transcranial magnetic stimulation. The second aim is to assess the impact of tSCS on spasticity and hypertonia in CP. To achieve this aim, the same electrophysiological measurements of spinal excitability will be repeated during non-invasive transcutaneous spinal cord stimulation in patient-participants (children with CP).

Inclusion Criteria:

A. Patient-Participant Group (Children with Cerebral Palsy)

• Children aged 5 to 17 years with a confirmed diagnosis of cerebral palsy.
• Gross Motor Function Classification System (GMFCS) Levels I to IV, able to walk with or without assistance (walker or cane). This classification will have been completed by Dr. Martin Piazza and his Movement Disorders clinic team.
• Stable medical condition without recent surgeries or interventions that could affect motor function.
• Must be able to communicate basic needs and follow simple instructions.
• Provision of informed consent by a parent or legal guardian, with assent from the child as appropriate.

B. Control Group (Children without Neurological Diagnoses)

• Children aged 5 to 17 years with no history of neurological diagnoses.
• Must be fully ambulatory without assistance.
• Must be able to communicate basic needs and follow simple instructions.
• Provision of informed consent by a parent or legal guardian, with assent from the child as appropriate.

Exclusion Criteria:

• Presence of implanted medical devices (e.g., baclofen pumps, deep brain stimulators) that may interfere with TSCS.
• Severe scoliosis or spinal deformities that could affect the delivery of tSCS.
• Uncontrolled epilepsy or a history of frequent seizures.
• Severe cognitive impairments limiting the ability to comply with study procedures.
• Skin conditions or open wounds at the site of stimulation.
• Participation in other interventional studies that may confound results.
• Any serious disease or disorder (e.g. cancer, severe cardiac or respiratory disease, etc.) that could affect ability to participate in this study.