Health Watch -- Fuel for Exercise

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A can of soda may be just the fuel some people need to exercise.

Many of us may find it hard to get up and go, but people with a rare disease truly do have trouble exercising. McArdle 's disease is caused by an enzyme deficiency that keeps muscles from using their stored fuel. People with this disease get tired very easily when they try to exercise, and they're at high risk for muscle injury.

Just walking up a slight incline is enough to wear these people out. Doctors have found that giving patients with McArdle's disease intravenous glucose before exercise helps them exercise more easily, especially during the early part of an exercise session when they're more prone to injury.

But now researchers at UT Southwestern Medical Center at Dallas have found that it's even easier to give these patients the fuel they need to exercise. They discovered that drinking a can of soda - or equivalent snack -- before exercising can dramatically improve exercise tolerance. In the study, patients were given either a can of caffeine-free diet soda or a can of caffeine-free regular soda.

The patients who drank the sugar-free soda reacted to exercise like McArdle's disease patients usually do - tiring easily in the early stages, then getting a second wind. Patients who drank the sugared soda tolerated exercise better, with a lower heart rate in the early stages.

Dr. Ronald Haller, the UT Southwestern doctor who led the study, said this condition is fairly rare, striking about one in 100,000 people. And these people are often accused of just being out of shape.