Autonomic Effects of Spinal Cord Stimulation in Spinal Cord Injury

The goal of this interventional crossover study is to determine the effects of transcutaneous spinal cord stimulation (TSCS) on the ability to perform moderate exercise and regulate core body temperature in the chronic spinal cord injury community. The main questions it aims to answer are:

* What are the effects of active TSCS targeted for BP control on exercise endurance time and HR recovery during submaximal arm cycle ergometry (ACE) as compared to sham TSCS in participants with chronic, cervical SCI?
* What are the effects of active TSCS on Tcore responses to cool ambient exposure and on subjective reporting of thermal comfort and thermal sensitivity as compared to sham TSCS.

Participants will receive sham and active stimulation while using an arm bicycle or while in a cold room. Participants are free to participate in either the exercise phase, the cold room phase, or both phases of this study.

Please note that there no expected long term benefits of this study.

The purpose of the first part of this research study is to determine the effects of active transcutaneous spinal cord stimulation (TSCS) targeted for blood pressure (BP) control on exercise endurance time and heart rate (HR) recovery time during an arm cycle test. The results will help guide experimental studies aimed at improving exercise, rehabilitation, health, and longevity in the SCI population. If the participant chooses to participate in part one of this study, the participant will be asked to visit the laboratory for 2 visits that take about 3-4 hours each.

The purpose of part two of this study is to compare the effects of electricity being delivered through surface electrodes (sticky pads on the participants skin), called active transcutaneous spinal cord stimulation (TSCS), compared to sham TSCS (sticky pads with electricity initially turned on but then turned off) on the participants ability to 1) keep the participants body temperature stable and 2) feel comfortable, while in a cool environment (cool room at 64° F) for 90 minutes. The investigators will assess the participant thermal sensation by asking the participant if overall they feel cold, cool, neutral, warm, or hot and their comfort level by asking the participant to grade their thermal comfort (how comfortable or how uncomfortable they feel) when the participant is seated in a thermoneutral room (80° F) and again in the cool room with active TSCS compared to the cool room with sham TSCS. The results will help guide experimental studies aimed at improving health and longevity in the population with SCI. If the participant chooses to participate in this study, there will be 2 study visits that last about 3-4 hours each.

Eligibility Criteria:
Inclusion Criteria:

* You are above the age of 18 years old
* You have an SCI between C3-T6
* You have been injured longer than 1 year
* You participated in a prior experiment "Targeted Transcutaneous Spinal Cord Stimulation to Restore Autonomic Cardiovascular Health in Individuals with Spinal Cord Injury"
* You have an American Spinal Injury Association injury classification scale (AIS) A, B, C
* Your prescription medications have not changed for at least 30 days

Exclusion Criteria:

* You have a history of seizures
* You have an acute illness or infection
* You have diabetes
* You have untreated thyroid disease
* You have a neurological condition other than SCI (Alzheimer's disease, dementia, stroke, multiple sclerosis, Parkinson's disease, etc.)
* You have a history of heart or vascular disease (coronary artery disease, congestive heart failure, peripheral artery disease,)
* You have a history of moderate or severe head trauma (TBI) or diagnosed with cognitive impairment
* You have a present or history of a psychological disorder
* You have contraindications to electricity over your spine
* You are dependent on a ventilator to breathe or have an open tracheostomy site
* You have a recent history of substance abuse (within the past 3 months)
* You have open wounds over the spine at the level targeted for stimulation
* You are pregnant