Diabetics should lift weights before cardio

People with type 1 diabetes may have better blood sugar control during workouts if they lift weights before cardio exercise, according to a new study by Canadian researchers.

It's important to define the best way for people with type 1 diabetes to exercise so that blood sugar doesn't drop too low, yet they can still reap all the benefits of aerobic exercise, Dr Ronald Sigal, an endocrinologist at the University of Calgary in Canada and lead author of the study said.

Twelve fit people with type 1 diabetes, which already ran and lifted weights at least three times per week, participated in the new study. The 10 men and two women were an average of 32 years old.

They met researchers at the laboratory for two experimental exercise sessions, which were held at least five days apart. At one session, they ran on a treadmill for 45 minutes and then lifted weights for 45 minutes. They switched the order for the other session.

Blood sugar drops with aerobics

Each workout started at five o'clock in the evening to simulate a common time of day people might exercise after work, said Dr Sigal.

Researchers interrupted participants if their blood sugar fell below 4.5 mmol/L; in that case, participants stopped and ate a snack.

When participants did aerobic exercise first, blood sugar dropped closer to that threshold and remained lower for the duration of the workout than when they lifted weights first and ran second.

Lifting weights first was also associated with less severe drops in blood sugar hours after exercise, and post-exercise drops that did occur tended to last a shorter period of time.

Muscles utilise sugar quickly

The results, published in Diabetes Care, support previous research showing that aerobic exercise causes a more rapid decrease in blood sugar than weightlifting.

"Your muscles utilise sugar very quickly in aerobic exercise," Dr Vivian Fonseca, chief of endocrinology at Tulane University Medical School, told Reuters Health. Dr Fonseca was not involved in the current work.

The study was small, and the researchers acknowledge that other factors, which they did not measure, could be at work, rather than the exercise order. For example, they did not account for levels of a number of hormones that could also lead to changes in blood glucose during exercise.

Nor did they have control over participants' food and activity choices prior to exercise –the authors wanted the study to reflect real-life conditions faced by people with type 1 diabetes.

Study has limited practical value

Because study participants were young, active people with Type 1 diabetes, it's not clear whether the findings would apply to less fit people with type 1 diabetes or people with Type 2 diabetes.

"While the study findings are very intriguing, they may have limited practical value until more studies are done," said Dr Fonseca.

Still, the authors conclude, people with type 1 diabetes who tend to develop low blood sugar during exercise "should consider performing their resistance exercise first."

(Lindsey Konkel, Reuters Health, March 2012) 

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