NEW YORK – A few minutes of intense exercise a week is just as good as a half-hour of moderate physical activity a day for reducing a person's risk of developing type 2 diabetes — and may actually be even more effective, new research hints.
"It is possible to gain significant health benefits from only 7.5 minutes of exercise each week — if that is all that you find the time to do," Dr. James A. Timmons of Heriot-Watt University in Edinburgh, one of the researchers on the study, told Reuters Health.
"This is a dramatically different view from current thinking," he admitted.
Timmons and his team found that young sedentary men who did just 15 minutes of all-out sprinting on an exercise bike spread out over two weeks substantially improved their ability to metabolize glucose (sugar). Traditional aerobic exercise programs can boost sensitivity to the key blood-sugar-regulating hormone insulin. The high-intensity program did this too, but it also directly reduced the men's blood sugar levels — something that standard exercise programs have not been shown to do.
Current exercise guidelines recommend at least 30 minutes of exercise a day at least five days a week, but "the general population fails to follow such regimes due to lack of time, motivation and adherence," the investigators note in the journal BMC Endocrine Disorders. They hypothesized that high intensity exercise might improve insulin sensitivity more efficiently.
To investigate, they had 16 men in their early 20s do six sessions of exercise, each including four to six 30-second sprints interspersed with four-minute rest periods. The time commitment for each session ranged from 17 to 26 minutes.
After two weeks, the amount of time the men's blood sugar and blood insulin levels were above normal after they drank a solution containing 75 grams of glucose was reduced by 12 percent and 37 percent, respectively. When people eat, Timmons explained, their blood sugar levels rise, but in very fit people levels speedily return to normal. In less-active people, high blood sugar levels are more prolonged, which over time can damage the body and lead to cardiovascular disease.
Based on the findings, Timmons told Reuters Health, people should try for four to six 30-second bouts of intense exercise, such as cycling or running up stairs, twice a week. While this is appropriate for people 20 to 40 years old who are in good health but not fit, he added, people with diabetes or heart disease should gradually increase their activity under a doctor's supervision.
Recommendations for high intensity, short duration exercise could one day replace current physical activity guidelines, Timmons said. "Only large scale trials could prove this," he said. "But there is mounting evidence that doing this new protocol will deliver the same reductions in risk factors. The key thing with exercise is the more routine you make it, the more likely you will benefit." And doing seven minutes of exercise a week, every week, he added, may be better than doing three hours a week just a few times a year.