December 12, 2011

Exercising Harder — And Shorter — Can Help Type 2 Diabetes

Regular exercise has proven benefits in preventing and treating type 2 diabetes, but many patients find it tough to meet the American Diabetes Association guidelines of 150 minutes of moderate to vigorous exercise a week. A new study, conducted by researchers at McMaster University, suggests that there could be a better way. In a small proof-of-principle study in eight type 2 diabetes patients, the researchers found that exercising at a very high intensity, but for a mere 30 minutes a week within a 75 minute total time commitment, lowered overall blood sugar concentrations, reduced post-meal blood sugar spikes, and increased skeletal mitochondrial capacity, a marker of metabolic health. The findings suggest that exercising harder, but in a significantly shorter amount of time, could provide benefits similar to longer, but more moderate, activity.

The article is entitled "Low-Volume High-Intensity Interval Training Reduces Hyperglycemia and Increases Muscle Mitochondrial Capacity in Patients with Type 2 Diabetes." It appears in the current edition of the Journal of Applied Physiology, published by the American Physiological Society.


Working with eight type 2 diabetic volunteers recruited through local diabetes clinics, information sessions, and advertising, the researchers gave each individual a baseline exam to test blood sugar over a 24-hour period, assess fitness levels, and take biopsies of thigh muscle to measure muscle mitochondrial protein levels. For the next two weeks, the researchers showed up for a total of six supervised training sessions. Each session involved pedaling on a stationary bike for 10 repetitions of 60 seconds apiece at about 90 percent of maximal heart rate, interspersed with 60 seconds of rest, capped by a short warm-up and cool-down. Each entire exercise session lasted 25 minutes of which only 10 minutes was spent performing vigorous intensity exercise. After the two-week training period, the researchers reassessed each volunteer's blood sugar and fitness levels and took a second muscle biopsy.


The results showed significant improvement in several measures of diabetic health. All the volunteers had lower 24-hour average blood sugar concentrations, and blood sugar spikes after breakfast, lunch, and dinner were significantly reduced. The muscle biopsies revealed higher amounts of mitochondrial proteins, suggesting that the high-intensity, low-volume training increased the numbers of muscle cell power generators, a marker of improved metabolic health. Although the training regimen didn't decrease body mass in any of the participants, it did increase the maximal workload that each was able to achieve on the stationary bike and decreased heart rate during exercise, markers of improved fitness.

Importance of the Findings

These findings suggest that exercising at a very high exertion level, but for a decreased amount of time, could have significant benefits for diabetic patients that rival those of traditional, but lengthy, periods of moderate exercise. Participants did not lose weight during the study, but the increase in mitochondrial proteins suggests that the training regimen changed their body compositions. The authors suggest that body composition change could be responsible for the effects observed in this study, but future research will be necessary to identify the true mechanism behind these results.

"Given that the majority of individuals with and without type 2 diabetes do not accumulate sufficient exercise to achieve health benefits, and the most common cited barrier to regular exercise is a lack of time, our results suggest that low-volume high-intensity training may be a viable, time-efficient strategy to improve health in patients with type 2 diabetes," the authors say.

Study Team

The study was conducted by Jonathan P. Little and his colleagues, Jenna B. Gillen, Michael E. Percival, Adeel Safdar, Mark A. Tarnopolsky, Zubin Punthakee, and Martin J. Gibala, all of McMaster University, and Mary E. Jung of the University of British Columbia Okanagan.


On the Net: