'Burst' Exercise May Improve HbA1c, Lipids in Type 2 Diabetes

October 29, 2015

TORONTO, ON — Short bursts of high-intensity exercise resulted in a significant improvement of cardiometabolic risk factors when compared with a traditional sustained-exercise program in a small group of patients with type 2 diabetes, a new study shows[1].

Presenting the results here at the 2015 Canadian Cardiovascular Congress (CCC), investigators, including senior researcher Dr Paul Poirier (Université Laval, Quebec City, QC), report that diabetic patients who engaged in "burst exercise" had significantly larger reductions in HbA1c, LDL cholesterol, and triglyceride levels, as well as larger increases in HDL cholesterol, compared with those who participated in a sustained-exercise program.

"Quite frankly, the reduction in HbA1c was as good as adding a drug," Poirier told heartwire from Medscape. "From a class effect, when you have one antihyperglycemic drug, you're treating only diabetes, but with the burst exercise, you're treating diabetes and you're also treating lipids."

The study was conceived and led by Avinash Pandey, a high school student at Waterloo Collegiate Institute. Poirier said that high-intensity interval training has gained in popularity in recent years but has never been tested in patients with type 2 diabetes. One reason is that high-intensity bursts of exercise in such patients typically leads to short-term increases in blood glucose postexercise. However, while the short-term increase might be expected, they wanted to determine whether longer-term exposure to the burst-exercise program would translate into a benefit.

"At the beginning, I thought blood glucose levels would increase," said Poirier. "It's not dangerous, it's not a health hazard by any means, but if you want to train somebody with diabetes with a 5-minute burst of exercise, and you measure blood glucose before and after each burst of exercise, the participant will tell you, 'Exercise is no good for me because it makes my blood glucose worse.' "

The conventional sustained-exercise program involved 30 minutes of physical activity designed to achieve a target heart rate of 60% of the age-predicted maximum. In contrast, the burst-exercise program involved three bouts of 10 minutes aiming to achieve a target heart rate of 85% of the age-predicted maximum.

The study was relatively small, with just 76 patients randomized to the two exercise programs. On average, patients were older, mean age 65 years, and overweight, with a body-mass index (BMI) of 31 kg/m2. At baseline, the mean HbA1c, LDL cholesterol, HDL cholesterol, and triglyceride levels in the burst-exercise arm were not statistically significant from those randomized to sustained exercise. The mean HbA1c level was 8.18% and 8.14% in the sustained- and burst-exercise arms, respectively. Average LDL-cholesterol levels in both arms was 128 mg/dL.

After 3 months of participating in the exercise programs, HbA1c was reduced 0.25% in patients participating in conventional physical activity and 0.82% in patients randomized to the high-intensity burst sessions, a difference that was statistically significant.

There was a small reduction in LDL-cholesterol levels, down 6.2 mg/dL in the sustained-exercise arm vs a reduction of 14.3 mg/dL in the burst-exercise group. This between-group difference was statistically significant. HDL-cholesterol levels were also modestly improved with burst exercise and almost unchanged with sustained exercise, and this between-group difference was also statistically significant. Triglyceride levels were reduced 76 mg/dL among those who participated in the burst-exercise program, a reduction that was significantly larger than the 15-mg/dL decrease observed with the sustained-exercise program.

Notably, adherence to the burst-exercise program was significantly better than the conventional recommendation of 30 minutes of sustained exercise (460 minutes vs 362 minutes; P=0.006). Given the differences in the amount of exercise, the researchers performed an analysis restricted to individuals with equivalent amounts of exercise time and still observed a significant decrease in HbA1c with burst exercise, as well as an improvement in the other cardiometabolic risk factors, when contrasted with sustained activity.

Patients in the study were all newly diagnosed with diabetes, noted Poirier. The reason is that investigators had to be cautious about silent ischemia, which exists in 20% to 30% of patients with long-term diabetes, he said. The current study did not include screening with exercise testing.

"We always need more research, because it is short term," said Poirier. "In an exercise study, 3 months is good to show proof of concept, but we need to have longer-term data. But right now, it's very interesting. What we can say for sure is that [burst exercise] is safe and effective in the short term. It's as good as adding a medication."

Poirier and Pandey report no relevant financial relationships.

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