Don't Get Burned by Calorie Counters

Human and equipment errors can overestimate calories burned during exercise.

Feb. 28, 2010— -- One thing everyone sweats at the gym is the question of what makes a good workout.

For those who rely on exercise machine calorie counters to determine results, the numbers might work everyone up, but they aren't necessarily working everyone out.

The Science

The VO2 analyzer assesses a user's calories lost during exercise by tracking breathing patterns. First, the user puts on headgear similar to a scuba mask and snorkle. The snorkle is attached to a long tube that is hooked into the VO2 analyzer. Finally, the analyzer records the user's breathing pattern as he or she inhales and exhales during exercise. Depending on the quality of breathing, the VO2 analyzer calculates how hard the user is working and combines that data with the user's body stats: height, weight, age, and body fat. The VO2 analyzer can then compute how many calories are burned during the exercise.

This measurement reflects someone's fitness and can be broken down to determine how many calories one burns.

The Experiment

On average, the machines overestimated by 19 percent and the watches overestimated by 28 percent.

Here's the breakdown:

The Analysis

"I think the estimations are just that. You can't necessarily believe everything you read on those machines," Smith said.

While the calorie counters are based on VO2 data, the calculations are susceptible to many variables based on the user's height, age and body fat that could skew data, Smith said.

Manufacturers Respond

According to the makers, calorie counting software doesn't adjust to machine wear and tear. Also, machine resistance can change overtime, which skews the calculation. And none of the machines can calculate a user's metabolism rate, health history and fitness level, all of which affect calorie counters.

Maximizing the Workout

Machines can't tell if a user is leaning on the handles, which makes the workout easier. Also, an individual's body can get used to a machine and exercise, and burn fewer calories because of it.

Physiologists recommend entering a slightly lower weight to compensate for the overestimation.

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