Joshua Kelley and Lance Davidson, Department of Exercise Science Department
In the past decade severe obesity (body mass index of greater than 35 kg/m²) has increased by 70 percent and is considered the fastest growing BMI category in the United States. Severe obesity has been linked with a low quality of life and a variety of comorbidities. As a result, the amount of various weight loss surgeries have dramatically increased, enabling individuals to lose large amounts of weight in a short period of time. Following Roux-en-Y-Gastric-Bypass surgery, 30-35 percent of the total weight lost is considered muscle mass or fat free mass (FFM) and a 20-40 percent decrease in muscular strength. Recent studies indicate a loss of FFM up to five years after surgery even when they start to regain weight.
General exercise interventions have been unsuccessful in retaining muscle mass. Skeletal muscles are stimulated and contract in two ways: muscle shortening (concentric) and lengthening (eccentric). Concentric contractions such as the upward motion of a bicep curl shortens the biceps muscle; in contrast the eccentric motion occurs with the downward motion of the curl, the biceps lengthen preventing the weight from falling.
Eccentric muscle contractions have shown to be more effective than standard resistance exercises in moderate energy-restrictive weight loss trails. Eccentric contractions can produce more force with only a fraction of the energy cost. Because muscular force is a stimulant for protein pathways, we posit that the energy deficiency of severe weight loss individuals may not have adequate fuel sources to create high levels of force with concentric contractions to stimulate adequate protein synthesis. Greater forces, as seen in eccentric contractions, should be able to trigger greater levels of protein synthesis, causing greater muscle hypertrophy and preventing the loss of FFM.
For the entirety of the research project twenty individuals that were 4-6 weeks post weight loss surgery will participate in a 16-week exercise program. Currently only three participants have started. We underestimated the recruitment process of this study and have had much difficulty in acquiring adequate participation because of the small population. Very few patients receive surgery from Intermountain Surgical Center and an even smaller percent receive the specific surgery that affects absorption properties. Participants have been recruited through pre-operation meetings at Intermountain Surgical Center or referred from physicians performing the surgery. Recruiting will continue throughout the year until twenty participants have been selected. We also may expand our recruiting efforts to surgical centers in parts of Salt Lake City to reach potential subjects that live close to Brigham Young University.
The twenty participants will be divided into three groups: control, concentric, and eccentric. All participants will receive a pre-assessment MRI and baseline strength and endurance tests. Baseline muscle strength will be measured by two methods: single leg-press one repetition maximum, and a BIODEX dynamometer. Muscle quality is measured by an MRI machine to take a continuous multi-slice magnetic resonance imaging scan of the lower body, from L4-L5 intervertebral space through the toes. The scan allows us to analyze the proportion of adipose to lean skeletal muscle tissue in the legs and gluteal regions. Functional capacity is measured with two tests: 30 second stand-sit test, and a six-minute walk test. Functional capacity and muscular strength will also be assessed every four weeks. Quality of life is also being assessed through a survey. Activity levels are measured in two ways at baseline and will be assessed when participants complete their exercise program. Acrigraph accelerometers will be placed on participants during the first and last weeks of the study. Participants also track the corresponding week of physical activity via a physical activity questionnaire.
Because of the duration of the study, tardiness of IRB approval, and lack of participants, no participant has successful completed the full training program. However, one exercise participant has doubled their starting one-repetition maximum and has increased in all areas of functional capacity and performance. In the exercise group, we have already seen an increase in muscular strength and are waiting for more data to compare the different exercise groups.
Although no current data is accessible, we have successfully laid a groundwork to continue through the upcoming year. We have been able to set up the exercise protocol and an MRI protocol to analyze physiological changes. We have programmed accelerometers and set up a protocol to measure the metabolic rate of participants. I have also participated in recruitment sessions with surgeons at the Intermountain Surgical center. With time, we will be able to recruit enough participants to complete the study and analyze the data that will be extracted from this project.