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December 13, 2011
Exercising Harder and Shorter Periods Helps Reduce Disease

Regular exercise has proven benefits in preventing disease, but many patients find it tough to meet the 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.

Doing bursts of hard exercise not only improves cardiovascular fitness but also the body's ability to burn fat, even during low- or moderate-intensity workouts.

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.

After interval training, the amount of fat burned in an hour of continuous moderate cycling can increase by 36 percent. The ability of the heart and lungs to supply oxygen to working muscles can improve by 13 percent. Results are independent from any type of special dieting or food plans.

For anyone with heart disease or high blood pressure -- or who has joint problems such as arthritis or is older than 60 -- experts say to consult a doctor before starting interval training.

Still, anyone in good health might consider doing interval training once or twice a week. Joggers can alternate walking and sprints. Swimmers can complete a couple of fast laps, then four more slowly.

There is no single accepted formula for the ratio between hard work and a moderate pace or resting. In fact, many coaches recommend varying the duration of activity and rest.


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.

Reduced Disease

Adults who do not get regular, vigorous exercise -- which includes nearly two-thirds of the study population -- have twice the risk of functional decline as their active peers the researchers have reported in the journal Arthritis & Rheumatism.

Researchers writing in the open access journal BMC Cancer who investigated the link between breast cancer and exercise, found that post-menopausal women who engage in moderate to vigorous exercise have a reduced risk of breast cancer. Vigorous exercise has been hypothesized to reduce cancer risk for some time. However, this new study is one of the first prospective investigations to look at the importance of various intensities of exercise at different stages in an individual's life.


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