Pilot Study of Strength Testing in Overweight Women With or Without Insulin Resistance

Overview

Background: \- Some people who are obese may have decreased muscle strength. They may have greater muscle mass shown in scans, but they show poor results in exercise tests. Poor muscle strength might cause some of the difficulty with exercise performance. Researchers want to test muscle strength in the arms and legs of overweight women. They will also see how insulin resistance affects muscle strength in these women. Objectives: * To test muscle strength in overweight women. * To see if insulin resistance affects muscle strength. Eligibility: \- Women at least 18 years of age who are overweight (body mass index greater than 25 kg/m2). Design: * Participants will be asked to fast before having an initial blood test to measure glucose and insulin levels. * On a different day, they will have the strength testing. The first test will measure leg muscle strength by testing the quadriceps and the hamstrings. The second test will measure arm muscle strength by testing the biceps and triceps. The final test will measure hand muscle (grip) strength. * All the tests should take about an hour.

We have observed in our protocol (08-H-0108: Effects of Worksite Wellness Interventions on Vascular Function, Insulin Sensitivity and High-Density Lipoprotein in Overweight or Obese Women) that despite increased lean (muscle) mass in the extremities as measured by dual x-ray absorptiometry, obese women have poorer exercise tolerance than overweight women who have less muscle mass.1 Exercise testing, however, is an integrated function of cardiopulmonary capacity, in addition to muscle strength and endurance. We propose to determine whether muscle strength of elbow flexors and knee extensor muscle groups correlates with muscle mass of these groups in overweight and obese women selected for normal or abnormal insulin sensitivity. Our hypothesis is that subjects with impaired insulin sensitivity and high insulin levels will have greater muscle mass but lower muscle strength than subjects with normal insulin sensitivity and normal insulin levels. This is a feasibility study to be conducted in 10 non-diabetic women (5 with insulin resistance, 5 with normal insulin sensitivity) who previously participated in 08-H-0108, the outcome of which will provide data for planning a larger study of muscle mass and strength which may be important to achieving exercise goals important to successful weight loss.