Effects of intensity and volume on insulin sensitivity during acute bouts of resistance training

This study evaluated the effects of various resistance exercise protocols on 24-hour postexercise insulin sensitivity. Seventeen participants with impaired fasting glucose (100-125 mg/dL) completed 4 separate bouts of resistance exercise under moderate intensity (65% 1 repetition maximum [1RM]) or high intensity (85% 1RM) conditions within the confines of single set and multiple set protocols. Intravenous fasting blood was taken at baseline and 24 hours postexercise for each exercise condition to measure fasting plasma glucose (G0) and fasting serum insulin (I0) to calculate insulin sensitivity (homeostasis model assessment-insulin resistance = (G0*I0)/405). A minimum of 3 days washout was given between each exercise protocol. A 4 x 2 factorial analysis of variance was performed to compare insulin sensitivity and fasting glucose within subjects and between treatments. All of the exercise protocols improved subsequent insulin sensitivity (p = 0.002) and G0 (p = 0.001). In comparison with single set, there was a significantly greater decrease in G0 (p = 0.021) 24 hours after multiple set bouts. High intensity showed significant decreases in insulin sensitivity as compared with moderate intensity protocols (p = 0.046). Effect size data suggest a dose response relationship between program variables of volume and intensity and 24-hour postexercise insulin sensitivity. High-intensity protocols resulted in greater effect sizes for insulin sensitivity (0.83 multiple set; 0.53 single set) as compared with moderate-intensity protocols. The high-intensity, multiple set bout yielded the greatest treatment effect in both fasting glucose (0.61) and insulin sensitivity (0.83). Overall, single set protocols were less effective than multiple set protocols in lowering fasting blood glucose. Findings suggest a dose-response relationship between volume and intensity on insulin sensitivity and fasting blood glucose. Results indicate that resistance exercise is an effective treatment for acutely enhancing insulin sensitivity and regulating blood glucose in individuals with impaired fasting glucose.