Which exercise machine counts calories best?

Chicago Tribune (MCT) - Problem: You are trying to lose weight and want to know many calories you're burning while on cardio equipment. Which provides the most accurate calorie count: a stationary bike, a treadmill or an elliptical machine?

Solution: Caloric expenditure is mostly (but not entirely) a function of distance covered and body weight. While the machines will never be 100 percent accurate, they can all give you a general idea of how many calories you burn, provided you input your correct weight.

"The bicycle predictions are the easiest to make, because the variation in people's mechanical efficiency is relatively low, and it's very easy to convert work 1/8in watts3/8 into calories, given what we do know about cycling efficiency," said exercise physiologist Ross Tucker, co-author of the exercise science blog The Science of Sport, sportsscientists.com.

On the treadmill, the efficiency of an individual's stride is more variable, Tucker said. "Assuming you're within 5 percent of the 'true value,' if your reading says you burned 600 calories per hour (or 10 calories per minute, a fast walk or slow run), then your range is probably within about 570 calories to 630," he said.

Unlike the treadmill, there are no standardized equations for caloric count on elliptical machines, said Doug Durnford, a senior product manager with Precor, which manufactures fitness equipment. So the accuracy "depends on the amount of due diligence performed by the manufacturer." Precor has funded a study looking at whether its equation _ which measures calories using gas exchange measurements _ is valid.

If you're concerned about precision, then "ask the manufacturer to confirm the method used to calculate calories expended and whether that method has been validated by independent study," said Durnford.

The real question, however, is whether the numbers mean anything. Yes, you'll lose weight if you burn more calories than you take in. But someone who burned 600 calories in one hour needs to consider what happens in the remaining 23 hours of the day.

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