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Lifting Weights before Cardio Benefits People with Diabetes

Mar 14, 2012

People with diabetes may have better blood sugar control during workouts if they lift weights before doing cardio exercise.

Dr. Ronald Sigal, an endocrinologist at the University of Calgary in Canada and lead author of the study explained that, “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.”

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.

In the study, 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 participated 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. 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 72mg/dL.(4mmol/L) to 180mg/dL.(10mmol/L). Researchers interrupted participants before blood sugar became too low for safety reasons — if it fell below 80mg/dL.(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 echoes previous research showing that aerobic exercise causes a more rapid decrease in blood sugar than weightlifting.

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.

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.”

Diabetes Care, online February 28, 2012