Article Title



Sam R. Emerson1, Mark D. Haub1, Brian S. Snyder2, Stephanie P. Kurti1 & Sara K. Rosenkranz1

1Kansas State University, Manhattan, Kansas; 2Truman State University, Kirksville, Missouri

Insulin resistance is associated with inflammation and both are thought to be precursors to type 2 diabetes and cardiovascular disease. Acute exercise can transiently attenuate insulin resistance and reduce systemic inflammation, however, the necessary exercise dose to produce improvements in inactive, non-insulin-resistant individuals is unclear. PURPOSE: The purpose of this study was to determine the exercise dose required to improve insulin sensitivity and inflammation in non-diabetic overweight men. We expected to see a dose-response relationship between exercise duration and insulin sensitivity and an association between insulin sensitivity and systemic inflammation. METHODS: In a randomized cross-over design, 11 inactive overweight men (BMI = 25-35 kg/m2) completed three trials: two exercise trials (brisk walk on a treadmill at 60% peak oxygen uptake [VO2peak] for 30 and 60 minutes; EX30 and EX60, respectively) and a control trial (60 minutes of passive activity; CON). Following a 12-hour overnight fast, a 10 mL blood sample was taken via indwelling catheter. Metabolic and inflammatory markers collected in the sample included plasma glucose, insulin, C-peptide, IL-6, IL-4, IL-10, IL-1ra, and TNF-alpha. Insulin resistance was determined via homeostatic model assessment (HOMA-IR). RESULTS: All individual values in CON were normal with regard to HOMA-IR (100 mg/dL). HOMA-IR was significantly lower following EX60 (0.58 ± 0.30) compared to CON (1.48 ± 1.12; p0.05) compared to CON or EX60. Plasma insulin was significantly lower after EX30 (3.85 ± 2.41 mU/L; p0.05) between trials for plasma glucose (CON: 5.21 ± 0.32; EX30: 5.03 ± 0.32; EX60: 4.86 ± 0.46 mmol/L). C-peptide was higher in CON (704.0 ± 497.8 pg/mL) compared to EX30 (399.7 ± 155.0 pg/mL; p0.05) between trials for IL-6, IL-4, IL-10, IL-1ra, or TNF-alpha. CONCLUSION: Thirty minutes of moderate-intensity walking was insufficient to improve insulin sensitivity twelve hours after exercise in a group of overweight, non-diabetic men. Sixty minutes of moderate-intensity activity, however, was effective in improving insulin sensitivity, but had no effect on markers of systemic inflammation.

(This work was supported by grant #0460017Z from the American Heart Association.)

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