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Here, experts dish on just how accurate your calorie readout really is on cardio machines at the gym.

To estimate it, scientists use a unit called themetabolic equivalent for task(MET).

This unit more or less measures how hard your body is working.

Reminder:Working out isn’t always about burning calories or losing weight.

Another estimate from theAmerican Council on Exercisesays that they can be as much as 20-30 percent off.

Why are elliptical machines so off base?

What’s so bad about that?

Leaning forward can decrease your total calorie burn by as much as 50 percent, says Olson.

“What you really need to know is how manymorecalories above your resting metabolic rate you are burning.”

), but it’s worth the sweat.

And we’re not just talking about the people who pull themselves up a hill for 20 minutes.

(More here:How Many Calories Do You Really Burn While Running?)

(Learn running form.)

If you’re free to, take your run outdoors whenever possible.

“Running outdoors is more difficult on the body,” he adds.

Can’t make it outside?

This is because when you stand and climb, you are no longer weight-supported."

How big is the difference?

(Just watch out for these otherspin bike workout mistakes.)

How to burn more calories on the stationary bike: Pedal with purpose.

You’ll burn fewer calories overall (seated or standing) if you pedal without enough resistance.

Try this30-minute stationary bike workoutthat’ll challenge you with intervals.

The Bottom Line

Take your calories-burned readout with a grain of salt.

“[An individual’s fitness level] is thebiggestfactor.

They don’t!”