Congratulations, You Burned 350 Calories?

I love that blinking message on the cardio machine after my workout, 'Congratulations, you burned 350 calories.' But did you actually burn 350 or was it more like 300 or 450? I wonder if those calorie estimates are accurate. Especially since I've always suspected the elliptical estimates are bogus. From experience, these machines report that I've burned way more calories than my sweat or effort justify.

Turns out some cardio machines are more reliable than others, and my hunch about that elliptical may be right. Listen to what the experts have to say:

• Bicycle Calorie Estimates Are Fairly Believable -- assuming you're not Lance Armstrong, the variation in gym-goer mechanical cycling efficiency is fairly low, so converting watts into calories is an easy conversion.
• Stride Matters on a Treadmill -- a person's stride efficiency is more variable on a treadmill, so your true calorie burn can fall above or below the 'true value' used to determine the machine's calorie calculation. If your stride efficiency falls within five percent of the 'true value' estimate of 600 calories per hour, you'd fall somewhere between 570 to 630 calories per hour. But how do I compare my stride against 'true value'?
  
• Ellipticals Have No Standardized Equations -- says one senior product manager with Precor, so the accuracy of an elliptical equation depends on the amount of testing completed by the manufacturer. What kind of testing have they done to prove the validity of their machine's equation? Precor has thrown some money at a study analyzing the validity of its current equation, which measures calories via gas exchange measurements.

Considering caloric expenditure is generally a function of distance covered and body weight, make sure you enter in a correct body weight. Maybe we're splitting hairs on this whole calories-burned question, but no matter how accurate the machine is, I still adore that blinking 'congratulations.'