Muscle-strengthening activity and its association with insulin sensitivity.

OBJECTIVE Muscle-strengthening activities (MSAs) may increase insulin sensitivity, thereby reducing the risk of diabetes. The purpose of this study was to assess the relationship between MSAs and insulin sensitivity among American adults. RESEARCH DESIGN AND METHODS We analyzed data on 4,504 adults without diabetes, aged 20-79 years, who participated in the National Health and Nutrition Examination Survey 1999-2004 and had information on MSAs. Self-reported frequency (times/week) of MSAs was grouped as low (<1), moderate (1-2.9), or high (>or=3). Insulin sensitivity was measured by the fasting quantitative insulin sensitivity check index x 100 (QUICKI). RESULTS After adjustment for age, race/ethnicity, physical activity other than MSAs, BMI, smoking, alcohol consumption, and daily total caloric intake, the mean values for QUICKI by low, moderate, and high MSA were 33.6, 33.9, and 34.2, respectively (P for linear trend = 0.008) for men and 34.2, 34.6, 34.6, respectively (P for linear trend = 0.009) for women. Mean fasting insulin (picomols per liter) concentrations were 75.0, 68.9, and 65.9, respectively (P for linear trend = 0.017) for men and 66.9, 63.3, 61.2, respectively (P for linear trend = 0.007) for women. There were no significant differences across MSA groups for fasting glucose among men or women. CONCLUSIONS MSA is independently associated with higher insulin sensitivity among U.S. adults. Efforts to increase MSA may be a realistic, feasible, and effective method of reducing insulin resistance among the U.S. population.