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Health and Human Physiological Sciences

Tortoise or the Hare? Which is better for Insulin Sensitivity, Glucose Tolerance and Inflammatory Cytokines?

Ben Clippinger, Tom Spinella, Eryn Relyea, and Danielle Bonitatibus

Dr. Paul Arciero


Currently, diabetes mellitus is extremely prevalent in America, approximately 7% of the population, or 20.8 million people in the United States suffer from diabetes. Two major types of diabetes are type I, also known as insulin dependent diabetes, and type II. Type I diabetes occurs when the beta cells in the pancreas do not produce insulin. Causes can be attributed to autoimmune, genetic and environmental factors. Type II diabetes usually is the result of advanced insulin resistance, where insulin is not used properly by skeletal muscle and liver cells.

To compare changes in insulin sensitivity as well as plasma cytokine levels following an acute bout of either endurance exercise (EE) (45 minutes at 70% VO2peak) or high intensity sprint interval exercise (SIE) (five 30-second sprints at 125% of the maximum resistance reached in the VO2peak).

Eight healthy, sedentary, non-smoking males between the ages of 18 and 22 were recruited to randomly complete the three days of testing: a baseline Oral Glucose Tolerance (OGTT) test (i.e., after familiarization, body composition, and VO2 peak procedures described above); 2) sprint interval ride (S) with an OGTT on the following day; and 3) an endurance ride with an OGTT. The SIE and EE session were randomized by flipping a coin.

The plasma glucose and insulin response during the oral glucose tolerance test (OGTT) was not significantly different among the three test conditions. There was also no significant difference in both glucose and insulin incremental and total area under the curve following all three testing days. EEOGTT produced a significant improvement in insulin sensitivity: *(P<0.05); compared with baseline testing. Average SIEOGTT was not significantly different compared to baseline and EE. Conclusion: Results indicate that EE compared with SIE result in significant improvements in insulin sensitivity. In future investigations of SIE in less healthy subjects, such as those with insulin resistance may show a more pronounced insulin sensitivity response. Pre-intervention tests found our subjects had a mean VO2 of 45.2 ml*kg*min-1, exercised 1.5 days per week and had a mean percent body fat of 16.5. It may be that the college students in our study were too healthy.