Arm and Leg Cycling for Accelerated SCI Recovery

The purpose of this study is to examine interventions with paradigms involving upper and lower extremity cycling (A\&L cycling) with A\&L cycling with functional electrical stimulation (FES) (A\&L_FES group), A\&L cycling with FES and transcutaneous Spinal Cord Stimulation (A\&L_tSCS group), and control Body Weight Supported Treadmill Training (BWSTT) to potentially restore functional abilities (i.e., walking) in individuals with an incomplete spinal cord injury. The researchers hypothesize there will be improved walking function following these interventional groups.

Spinal cord injury (SCI) occurs at an annual rate of 50-60 per million in North America. Paralysis is also accompanied by drastic changes in independence and quality of life. SCI occurs mostly among younger individuals, half in people 16-30 years of age. Two-thirds of all SCIs are incomplete (iSCI), with some preserved neural connections relaying information to and from the brain. People with iSCI benefit most from improvements in walking. In addition to increasing independence, walking helps persons with iSCI remain active, with a variety of beneficial health-related outcomes. Therapy that can significantly increase sensorimotor function to these individuals living with iSCI for multiple decades would be hugely significant.

Currently, the most common strategies for restoring walking after an iSCI are manually intensive, including over ground walking with weight and balance support provided by multiple therapists, or with the use of expensive robotic support with controversial outcomes. Thus, the overarching goal of this proposal is to investigate if a non-specific gait rehabilitation paradigm based on motor-assisted arms and legs cycling, motor-assisted arms and legs cycling with functional electrical stimulation (FES) to the main muscles of the legs (A\&L_FES group), or motor-assisted arms and legs cycling with FES to the main muscles of the legs and transcutaneous spinal cord stimulation (tSCS) at the cervical level (A\&L_tSCS group) in AIS C and D iSCI individuals generalizes to improvements in walking that outperform conventional gait specific training, e.g., body-weight supported treadmill training (BWSTT; control group) (clinical assessments). The researchers will also investigate biomechanical and motor coordination changes and adaptations tied to these functional improvements (biomechanical assessments), and the neural mechanisms that explain functional improvements and their retention over time (neurophysiological assessments).

In the clinical assessments the researchers will investigate the clinically-relevant gait improvements afforded by the cycling intervention by measuring the walking gains with a battery of standard clinical tests focused on motor function, sensation, balance and spasticity. In the biomechanical assessments the researchers will focus on studying the detailed biomechanical basis for the gait improvements by using motion tracking, force plates, and EMG measurement to monitor the kinematics and kinetics of gait, and neuromuscular coordination. In the neurophysiological assessments the researchers will investigate the neuroplastic mechanisms underlying the gait improvements by conducting a battery of physiological tests to detect changes in the strength of descending and ascending spinal pathways.

Eligibility Criteria:
Inclusion Criteria:

* Traumatic or non-traumatic SCI T11 and above (upper motorneuron lesion)
* Incomplete paraplegia or tetraplegia (Classified as AIS C or D)
* Age range 18-75 years old, inclusive
* At least 1 year post- injury
* Independent ambulator (with normal assistive devices or bracing) for at least 10 meters (30 feet)
* Walking speed \<0.8 m/s (2.62 ft/s) (or per researcher discretion)
* Bilateral arm strength to arm cycle at least 15 minutes without assistance (or per researcher discretion)
* No concurrent or planned surgeries, significant medical treatments, or therapy during the study period
* Able to understand and speak English

Exclusion Criteria:

* SCI T12 and below (or lacking upper motorneuron injury)
* Complete paraplegia or tetraplegia (classified as AIS A)
* AIS B incomplete paraplegia or tetraplegia
* Presence of progressive neurologic disease
* Unable to give informed consent to participate in the study
* Significant other disease (ex: cardiological or heart disease, renal, hepatic, malignant tumors, mental or psychiatric disorders) that would prevent participants from fullym engaging in study procedures
* Weight over 160 kg (352 lbs)
* TMS contraindications

  * Epilepsy, seizure disorder, or any other type of seizure history
  * Medications that increase the risk of seizures
  * Metal or metal fragments in the head (plates, screws, etc.)
  * Surgical clips in the head or previous neurosurgery
  * Implants in the head (ex: cochlear implants)
  * Non-prescribed drug or marijuana use
  * Depression, antidepressant medications, or antipsychotic medications
* FES and tSCS contraindications

  * Active Deep Vein Thrombosis (blood clot)
  * Active infection in the legs
  * Open wounds, rashes, or infection at the electrode sites
  * Cancer or recently radiated tissue
  * Cardiac pacemakers or neurostimulators
  * Hypersensitivity to or inability to tolerate electrical stimulation
  * Lower motor neuron injury or peripheral nerve injury in the legs that would prevent the muscles from responding to electrical stimulation
* Pregnancy
* Prisoners