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 told Reuters Health.

Those with type 1 diabetes, a condition in which the body does not produce its own insulin, a hormone needed to convert food into fuel, risk low blood sugar during exercise. Blood sugar that drops too low can lead to poor coordination, unconsciousness or even coma.

About five percent of all Americans with diabetes, or roughly 1.3 million people, have type 1, which is often diagnosed in childhood, according to the Centers for Disease Control and Prevention.

Twelve fit people with type 1 diabetes, who already ran and lifted weights at least three times per week, participated in the new study. The 10 men and two women averaged 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, participants did 45 minutes of treadmill running followed by 45 minutes of weight lifting. They switched the order for the other session.

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

Researchers measured blood sugar levels before, during and after exercise for each participant.

In people with type 1 diabetes, target blood sugar levels can range from about 4 to 10 millimoles per liter of blood (mmol/L).

Researchers interrupted participants before blood sugar became too low for safety reasons -- if it fell below 4.5 mmol/L, 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.

The current study, published in the journal Diabetes Care, echoes previous research showing that aerobic exercise causes a more rapid decrease in blood sugar than weightlifting.

“Your muscles utilize sugar very quickly in aerobic exercise," Dr. Vivian Fonseca, chief of endocrinology at Tulane University Medical School told Reuters Health. He 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.

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 Fonseca.

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

SOURCE: bit.ly/yItDRO Diabetes Care, online February 28, 2012.

• A Permanent Economic Emergency