If you have type 1 diabetes (the kind where your body can't produce insulin), then you know that regular exercise is essential because it helps keep blood sugar under control and reduces the chance of complications such as high blood pressure and high cholesterol.

But when you exercise, which do you do first-cardio/aerobic ... or strength training?

That may sound like a silly question, but a new study suggests that the order in which you do your exercises can make a big difference in terms of how well you control your blood sugar.

Using the Proper Fuel

To understand the new research, keep in mind that the human body can use either glucose or fats as fuel-and, of course, for people with diabetes, the level of glucose in the blood tends to be out of whack.

Now, in previous studies, it's been shown that in healthy people (who do not have diabetes), performing strength training immediately before aerobic exercise increases the body's use of fats-not glucose-as fuel. And insulin, which is key to the proper maintenance of blood glucose, plays a less important role when fats are being used as fuel. Therefore, researchers were curious to find out whether exercising in this particular order might better protect individuals with diabetes from hypoglycemia (low blood sugar).

Let's get moving

The research involved 12 men and women (average age 32) with type 1 diabetes who already lifted weights and ran at least three times a week. For the study, each participant completed two exercise sessions held at least five days apart. In one session, each subject ran on a treadmill for 45 minutes and then lifted weights for 45 minutes. In the other session, the sequence was reversed.

Both sessions were held at the same time of day and the participants ate the same foods the day before, the day of and the day after they exercised. Whenever a participant's glucose dropped too close to a hypoglycemic level during exercise, the exercise was interrupted and the participant was given a carbohydrate supplement to bring glucose back up. The participants were set up with continuous glucose monitoring starting the day before their exercise sessions and ending the following day.

Results: Those who performed strength training first were less likely to reach the hypoglycemic danger zone. In fact, 43% more glucose supplementation was needed when running came first.

Plus, the blood sugar benefits of strength training first lasted through the night. Researchers found that nighttime episodes of hypoglycemia were, on average, shorter (48 minutes rather than 105 minutes) and less severe following an exercise session that began with strength training.

Lift Before you Run

Why might strength training first have such a positive effect on blood sugar? Jane Yardley, PhD, the study's lead author, said that more growth hormone is secreted during anaerobic exercise (such as strength training), and growth hormone might increase the use of fats as fuel, rather than glucose.

Another possibility: Performing strength training first can cause lactate to circulate in the blood. Some lactate could be converted to glucose, so blood sugar wouldn't drop as quickly.

So should all people with type 1 diabetes strength train before doing cardio? Dr. Yardley recommends it, though she did point out one limitation to the study, which is that the participants were fit, and fit people may use glucose differently than people who aren't in such good shape. But whether you're fit or unfit, it wouldn't hurt to strength train first, said Dr. Yardley. Even if you can't handle 45 minutes of each type of exercise, it's not the total time that matters-it's the order.

Dr. Yardley commented on whether this advice would also hold true for individuals with type 2 diabetes. She explained that most type 2 diabetics are not insulin-dependent, so hypoglycemia isn't as big a risk. Therefore, the order in which they do those exercises isn't likely as critical.

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