"Just recognize that when they get on those machines and it shows them how many calories they are burning, it really is an estimate," said Todd Schroeder, assistant professor of research and the director of the Clinical Exercise Research Center in the USC Division of Biokinesiology and Physical Therapy.
Schroeder gave us some bad news. That number you see on the treadmill about how many calories you're burning? Not so accurate.
"People don't exercise at a continous level, they are always changing speed, grade of the treadmill, inclines, declines, things like that that will affect the work out," said Schroeder.
With so many factors involved, Schroeder warns, take a closer look on those workouts that claim super-high calorie burns.
One called BBX Hardcore touts you'll burn 1,100 calories an hour.
"Well, we say 'up to.' The guy, of course, the man -- we hate them all, whatever -- he burned the most calories," said Dede Barbanti, creator of BBX Hardcore.
After her divorce, Barbanti weighed more than 200 pounds and was suffering from depression. So she turned to an old love of dancing and developed BBX Hardcore workout and dropped 65 pounds in the process.
"Right now, in comparison to any other format out there this has the highest calorie burn in group fitness right now. We put it to the test, twice," said Barbanti.
We put her dancing, boxing, strength-training workout to a calorie-burning test drive with instructor Kathy Lamm at the USC lab. These tests, which can cost anywhere from $400 to thousands of dollars, measure how much oxygen is used which helps determine how many calories burned.
Along with this machine's measurements a lot of other factors come into play like your age, weight, gender, even body fat, but the most important is how much energy you put into play.
"People always ask me, 'Well, can I do this?' Well I don't know, how hard are you going to work out?" said Barbanti.
The answer should be, as hard as you can. Up the intensity, keep abdominal muscles contracted and tension in your muscles. Put full-force energy in your arms to up the calorie-burning. Other factors?
"Fitness as well. The more fit you are, how stressed you are, your hormone levels, your nutrition, so there are a lot of factors that go into that," said Schroeder.
Kathy and I were able to burn similar calories at around the 650 range. Not exactly 1,100, but the lab technicians were impressed.