Knowing that the top 3 lifestyle behaviors associated with glucose control—weight loss, diet, and exercise—can be challenging for physicians and patients to address all at once, Duke researchers conducted a study to measure the effects of exercise alone, in various amounts and levels of intensity, on glucose control. Researchers found that moderate exercise is better than vigorous exercise, marking a paradigm shift in the common belief that the harder a person exercises, the better.

“Our research team decided to find the answer to this question: If physicians address only one of the lifestyle behaviors with individuals at risk of prediabetes, what percentage of the maximum benefit would they experience? We chose exercise as the one behavior to study,” says William Kraus, MD, a Duke cardiologist and the principal investigator for Studies of a Targeted Risk Reduction Intervention with Defined Exercise (STRRIDE).

In the first 2 phases of STRRIDE, Duke researchers examined the effects of exercise training regimens with various amounts and levels of intensity on the cluster of risk factors associated with insulin resistance and metabolic dysfunction leading to cardiovascular disease. In STRRIDE Prediabetes, the research team used the National Diabetes Prevention Program (DPP) as the “gold standard” against which to measure results of exercise on glucose control, designing the 5-year study as a comparative effectiveness trial to answer the questions: (1) How much of the effect of the DPP can be achieved with exercise alone, and (2) What are the individual effects of exercise amount and intensity on glucose control measures—is moderate-intensity exercise the best?

STRRIDE Prediabetes study participants were randomized to the DPP-like lifestyle in 4 groups based on the amount and intensity of brisk walking and jogging during a 6-month exercise program: DPP group (diet, exercise, and 7% weight loss over 6 months); high amount/moderate intensity; high amount/vigorous intensity; low amount/moderate intensity. Outcome measures were the reduction in 2-hour and fasting serum glucose levels at 4 time intervals following exercise.

Matching the amount of exercise (high) but at different intensities (moderate and vigorous), researchers made a surprising discovery: the high-amount/moderate-intensity group had 3 times the improvement in glucose control during an oral glucose tolerance test as the high-amount/high-intensity group. “Exercising harder is not necessarily better,” reports Kraus, “and that’s a paradigm shift. We tend to think that you have to work harder to get better, but instead, we found that moderate exercise is better than intense exercise for glucose control; in other words, if one walks briskly, one gets better results than jogging the same distance.”

All 3 of the STRRIDE studies have demonstrated that exercise recommendations must be individualized to be effective, and Kraus stresses that a personalized approach to glucose control is vital. “For example, if a patient has a problem with fasting glucose, the recommendation would be for weight loss in addition to exercise. But if the problem is postprandial glucose levels, an exercise program is better than weight loss, and brisk walking is the best exercise for that patient,” he explains.

STRRIDE researchers are currently assessing results from the first 2 studies through a series of reunions for participants 10 years after the intervention. Results indicate that the effects of exercise are beneficial for lowering metabolic syndrome levels, and they are long-lasting. “A 6-month exercise program has health benefits years later, even if an individual doesn’t keep it up,” says Kraus.