Transcutaneous Spinal Electrical Stimulation to Improve Exercise Function After Spinal Cord Injury.

Overview

Our overall objective is to decrease the prevalence of multiple sedentary-related diseases that are secondary consequences of spinal cord injury (SCI). SCI affects motor, sensory and autonomic systems and can cause very limited exercise capacity which then leads to very high rates of obesity, metabolic syndrome, type II diabetes and cardiovascular disease. This randomized controlled study aims to determine whether and how transcutaneous spinal electrical stimulation (TSES) alters acute (immediate) exercise responses in people living with SCI. Exercise responses will be tested during incremental tests to fatigue, and during steady state tests. Testing will occur over several study visits and results will be compared within each individual as well as between groups (tetraplegia and paraplegia) and to a group of reference controls. A number of outcomes will be monitored, including whole-body metabolic responses using a metabolic cart, muscle responses using EMG sensors and muscle oxygenation using near infrared spectroscopy (NIRS) sensors, time to fatigue, power output, as well as perceptions about fatigue and effort. The findings of this study are expected to provide evidence regarding whether and how TSES might improve acute exercise responses in people living with SCI.

It is well understood that SCI causes motor paralysis and sensory loss. However, it is the loss of autonomic regulation that confers the greatest morbidity to those living with SCI. Impaired exercise responses, including limited peak HR, oxygen uptake, limited catecholamine related to impaired activation of spinal sympathetic autonomic systems. Depending upon level of injury, and these sub-optimal exercise responses, there are limited exercise training effects which then leads to a calorie excess and related weight gain, cardiovascular, skeletal muscle and metabolic deconditioning that eventually causes obesity, type II diabetes and cardiovascular disease. These sedentary-related diseases likely result in large part, because of inadequate activation of these tissues with sufficient duration or intensity to result in training effects. Therefore, we are interested in identifying means to improve acute exercise responses, with an ultimate goal of improving training responses and reducing the incidence of and/or trajectory of developing these sedentary-related diseases in individuals with SCI. TSES has recently emerged as a potential therapeutic method to improve exercise responses. In case studies it has been shown to increase peak responses and time to fatigue during arm ergometry exercise tests. This study is designed as a prospective, single-center, randomized controlled trial to examine whether and how TSES might alter exercise responses in two groups of people with SCI (tetraplegia and paraplegia) and a reference control group from the general population. The study is designed to assess within individual and between-group responses for a variety of outcome measures during peak and steady-state exercise tests. Study visits occur over several weeks for each participant, according to each person's time and convenience availability. Outcomes are assessed during exercise with and without TSES in the following 4 experimental conditions: 1. Comparing peak incremental tests to voluntary upper body exercise fatigue with or without TSES. 2. Comparing steady state exercise responses performed at 40-45% peak power output with or without TSES. 3. Comparing time to fatigue during neuromuscular electrical stimulation (NMES) evoked rhythmic leg contractions with or without TSES. The primary hypothesis is that TSES will improve a variety of exercise outcomes under different experimental testing conditions and that those with tetraplegia will benefit most. The results of this study are expected to contribute to whether and how TSES might alter acute exercise responses in those living with SCI. The results of this study are expected to contribute to the evidence base regarding the effectiveness of TSES to alter peak and steady-state exercise responses in people with SCI and may support its integration into standard exercise training or competitive sport protocols for individuals with SCI.