Obesity prevalence among individuals with SCI is about 66%. However, when the BMI formula is adjusted for the loss of muscle after SCI, the combined overweight and obesity rate is 70 to 75%. This places the SCI population across the U.S. at the top of the list in terms of obesity. Additionally, because greater obesity is related to greater disability and chronic diseases, the risk of cardiometabolic diseases, including heart disease, stroke and type II diabetes, are elevated to more than twice that of the able-bodied population. One reason for high obesity after SCI is the loss of muscle mass. Shortly after injury, those with SCI experience rapid and significant skeletal muscle atrophy below the level of injury resulting in skeletal muscle cross-sectional areas of 45-80% less than that of able-bodied individuals. Therefore, after SCI, the loss of metabolically active muscle mass results in a 26% reduction in basal metabolic rate and resting energy expenditure. This is important because basal metabolic rate accounts for \~65% of the total daily energy expenditure after SCI. In addition to decreased muscle mass, individuals with SCI are typically among the most sedentary, thus further lowering energy expenditure creating an unhealthy energy balance.

The benefits of physical activity for reducing obesity and cardiometabolic disease have been well documented. In particular, high-intensity interval training (HIIT) has been shown to decrease cardiovascular and metabolic risk among able-bodied individuals in a shorter period of time than standard non-interval exercise programs. For example, one comparison of interval walking to continuous walking in able-bodied adults with type II diabetes over a 6-month period. The continuous walking group walked for 60 minutes 5 days per week at a moderate intensity while the interval training group alternated between 3 minutes of high intensity walking and 3 minutes of low intensity walking 5 days per week. The walking intensities were determined by oxygen uptake (VO2) peak testing and energy expenditure, with moderate intensity being set at 55% and high intensity at 70% of VO2 peak. Although, the mileage was the same for both groups, the interval training group lost 4.3 ± 1.2 kg total body weight and 3.1 ± 0.7 kg body fat mass, whereas no changes in body composition were found in the continuous walking group or the non-walking control group. In a similar study, another researcher used leg cycling 3 times per week for 12 weeks in both the continuous and interval groups and determined intensity levels based on heart rate. The interval training group performed 3 "all out" cycling sessions of 20 seconds each separated by 2 minutes low intensity cycling, while the continuous group cycled steady at 70% of maximal heart rate for 45 minutes. Both groups improved similarly in insulin sensitivity, cardiorespiratory fitness, and skeletal muscle mitochondrial content, however, the interval training group achieved these benefits with a five-fold lower exercise volume and training time commitment.

A major consequence of SCI is that paralysis makes voluntary exercise with the legs impossible. In addition, the 60-90% prevalence of shoulder pain in persons with chronic SCI is often limiting the possibility of regular arm exercise. To circumvent these problems, FES has been shown to be a safe and effective way to exercise paralyzed leg muscles in clinical and home settings. High-cadence moderate-resistance FES cycling can increase muscle mass and improve fasting blood glucose values and low-cadence higher-resistance FES cycling can lead to hypertrophy of the paralyzed leg muscles. As a result of developing our new protocol, which incorporates resistance-guided high-intensity interval training into FES cycling (RG-HIIT-FES), we postulate that it may provide equal or greater benefits with less exercise time commitment, by analogy to high-intensity interval training programs used by able-bodied individuals. The advantage of using resistance as the determinant of exercise intensity is the fact that heart rate is an ineffective method for monitoring exercise intensity after SCI. Instead, we first determine the greatest resistance that stimulated muscles can work against while cycling at 35 rpm for 30 seconds, use 80% of that maximal resistance for the high-intensity cycling interval (30 seconds), and then decrease it to 0.5 Nm, which is the lowest resistance provided by the FES bike (RT300) for the low-intensity cycling interval (30 seconds). These intervals are then alternated for 30 minutes. In a proof-of-principle case series study using this RG-HIIT-FES cycling protocol 3 times per week for 8 weeks, 3 obese individuals with SCI increased legs lean mass (5-9%), improved vascular endothelial health (mean increase of 58% in arterial flow mediated dilation), and decreased HbA1c blood levels (2-4%). Two of the three participants decreased body weight and BMI.

It is important for proper interpretation of results not to overlook the significance of nutritional counseling concerning energy intake because food intake can have a major effect on body composition and health. Individuals with SCI are especially in need of nutritional counseling due to decreased energy expenditure from reduced metabolic muscle and decreased activity levels. Consequently, our central hypothesis is that a combined program of RG-HIIT-FES cycling and nutritional counseling will be effective in combating obesity and enhancing cardiometabolic health for those with SCI. Specifically, decrease total body weight and percent body fat, increase total and legs lean mass, improve blood lipid levels, decrease blood glucose and HbA1c levels and improve cardiovascular health markers (arterial flow mediated dilation) beyond that observed in the control group that will receive nutritional counseling alone. The intervention group will receive three 30-minute RG-HIIT-FES cycling sessions and one 30-minute nutritional counseling session per week for 8 weeks, whereas the control group will receive one 30-minute nutritional counseling session per week for 8 weeks.

Innovation: The proposed pilot study provides at least three important innovations: 1) the first formal implementation of a novel and promising FES cycling protocol (RG-HIIT-FES); 2) the first testing of potential benefits of combining FES cycling with nutritional counseling in any population; 3) enrollment of a medically underserved and disadvantaged population with limited options for battling obesity and maintaining cardiovascular health.

Planned Experimental Protocols: The hypothesis for our research aim is that combining RG-HIIT-FES cycling with nutritional counseling will be more effective than nutritional counseling alone for reducing obesity and enhancing cardiometabolic health markers in persons with chronic SCI. This will be tested using a subject-matched controlled pre-post design. Prior to and after the 8 weeks of experimental or control intervention, each participant will visit the SCI Research Laboratory during the morning hours (between 7:00 and 10:00 am), following an overnight fast and having refrained from caffeine and alcohol intake for 12 and 24 hours, respectively. After reviewing and signing the informed consent and medical history documents, participants will be weighed using a Scale-Tronix Wheelchair Scale (Welch Allyn, Skaneatelest Falls, NY). The weight of the wheelchair alone subtracted from the combined weight of the participant and wheelchair will provide the weight of the participant. An electric powered lift (Invacare, Reliant 450) will be used to provide safe transfers for all participants from the participant's wheelchair to various testing locations (e.g., exam table and DXA body composition scanner). Once on the exam table in a supine position, an anthropometric measuring rod will be used to measure height. The left leg will be extended and ankle dorsiflexed to enable an accurate measurement from the bottom of foot to top of the head. Following 20 minutes of quiet rest in a dimly lit and temperature (21-23°C, 50% humidity) controlled room, 5 minutes of resting hemodynamic data (hear rate and blood pressure) will be recorded followed by Doppler ultrasound vascular endothelial function testing, followed shortly after by a finger stick on the left hand for determination of blood lipid, glucose and HbA1c levels. The participants will then be transferred back to their wheelchair and taken to an adjacent laboratory in the same building for DXA scanning. Following the DXA scan, participants return to the SCI Research lab and complete a resistance guided FES cycle maximal test from there own wheelchairs in order to gain baseline parameters for the RG-HIIT-FES cycling protocol, and also to determine each participants ability to tolerate and safely perform the cycling program. Participants in the experimental/intervention group will then complete FES cycling as described above for 30 minutes, 3 times per week for 8 weeks and will receive nutritional counseling over the telephone for 30 minutes 1 time per week for 8 weeks. Then post-testing will occur in the same fashion as the pre-testing.