I get asked this question a lot and to be honest, I don't have a good answer nor do I care. Now, don't get me wrong, I do care about the results that our clients get, however the amount of calories burned during a workout isn't that important, and to be perfectly honest, it is probably a lot less than you would expect.
Most machines (treadmill, stationary bike, etc.) will give an estimate of calories burned in a workout. And they are typically wrong. While you may have worked your butt off, you probably didn't burn 500 calories in 30 minutes.
If we aren't burning that many calories when working out, then what is the point? While the amount of calories burned during a workout isn't anything to brag about, the amount of calories burned after a workout is!!!
The story goes like this.....
We want to add lean muscle mass because it is metabolically active. However, gaining one pound of muscle will only really increase your Basal Metabolic Rate (BMR) by about 10 calories per day. Again, nothing to brag about...
However, you take that same pound of muscle and "beat it up" (by working out) and that RECOVERING muscle will increase your BMR by up to 100 calories per day! Now that's what I'm talking about!!!
So when someone asks me how many calories they burned during an hour workout, I don't care because I am more concerned about the calories that will be burned in the remaining 23 hours of the day!