Type 2 diabetes can sometimes result in a loss of heart function. However, the results of a new study suggest this function may be recovered through high-intensity exercise.

Around 90%–95% of the 30 million people in the United States who have diabetes have type 2 diabetes. In type 2 diabetes, the body's cells become resistant to the effects of insulin, the hormone that helps to convert blood sugar into energy. With insulin unable to activate this energy conversion within cells, a rise in the body's blood sugar level occurs and creates the conditions for prediabetes and type 2 diabetes.

Elevated blood sugar levels can be very harmful, potentially causing vision loss and creating serious health problems within various organs, including the heart and kidneys.

Researchers behind the new study are from the University of Otago in Dunedin, New Zealand, and they have published their work in the American College of Sports Medicine's journal, Medicine & Science in Sports & Exercise.

They say that exercise is probably the best way to prevent heart disease among people with type 2 diabetes. They acknowledge, however, that one issue may be that many people with the condition have impaired heart function and so might be unable to train hard enough to receive the benefits of this exercise.

The Otago team put this to the test in their study, which focused on the benefits of high-intensity interval training (HIIT). HIIT involves short bursts of intense sprinting or stair climbing with alternate periods of moderate intensity exercise, such as jogging or fast walking.

HIIT for 3 months improves heart function

In the study, over the course of 3 months, 11 middle-aged adults with type 2 diabetes engaged in 25-minute exercise sessions that included 10 minutes of very high-intensity activity.

The team took measures of heart function from the participants at the start of the study and the end of the 3-month training period. They then compared these measures to a control group of five participants who did not undertake the training.

The study found that the participants who undertook HIIT demonstrated improved heart function after 3 months and that this result was without any changes to their medication or diet.

More importantly, the study demonstrated that the high-intensity program was a safe and viable exercise regimen for middle-aged adults with type 2 diabetes, with an impressive 80% adherence rate over the course of the study.

Scientists will need to reproduce the results in larger studies to be sure of the benefits of HIIT among people with type 2 diabetes.

Lead author Genevieve Wilson, who did the study as part of her PhD, says the team's findings demonstrate that high-intensity exercise may provide "an inexpensive, practical way to reverse or reduce the loss in heart function caused by type 2 diabetes." Wilson adds that this is important as the leading cause of death in type 2 diabetes patients is heart disease.

Dunedin School of Medicine senior research fellow Dr. Chris Baldi supervised Wilson's work with co-adviser, cardiologist, and associate professor in the Department of Medicine, Gerry Wilkins. Together, the researchers note that the study shows the HIIT program for middle-aged adults with type 2 diabetes was safe, and the participants were able to stick to it for the majority of the time.

"There are two important clinical implications of this work," Dr. Baldi maintains. "The first, that adults with type 2 diabetes will adhere to high-intensity interval training and are capable of comparable increases in aerobic capacity and left ventricular exercise response as those reported in non-diabetic adults. Secondly, high-intensity exercise is capable of reversing some of the changes in heart function that seem to precede diabetic heart disease," he continues.

Reducing the risk of heart complications

For those with type 2 diabetes, the National Institute of Diabetes and Digestive and Kidney Diseases recommend some useful steps to lower the risk of developing heart disease. These are the Manage your Diabetes ABCs:

• A is for the A1C test, which shows the average blood glucose level over the previous 3 months. For most people, the ideal A1C is below 7%, but a health-care team can help set the right goal
• B is for blood pressure. High blood pressure can cause a heart attack. The blood pressure goal for most people with diabetes is below 140/90 mm Hg.
• C is for cholesterol. Too much "bad" cholesterol (LDL cholesterol) in the body can clog up blood vessels, increasing the risk of a heart attack or stroke. Statins can help reduce this cholesterol
• S is for stop smoking. Diabetes and smoking both narrow blood vessels, forcing the heart to work harder. Quitting smoking lowers the risk of heart attack and other illnesses