Go to any gym in America these days and 75 percent of the gym goers have some type of device on that is tracking their caloric expenditure. This device is usually a heart rate monitor and watch combination. Now these can be a great tool to give yourself a general roundabout number of calories that you're burning during a workout session or class. They can also be great to track your heart rate so you know when your heart rate drops to a certain number that it's time to go again. However, the more I look into these the more I think that they are boasting your numbers of calories burned. Now I don't think it's by much but I think they exaggerate a bit. And that can lead to possible over indulging thinking you burned 300 calories when really you may have only burned 150.
The good news is that even if they're giving you some leniency on the calories being burned, no one accounts for the EPOC effect (or the after burn effect) that lifting weights gives you. Simply stated, the EPOC Effect: (Excess Post-Exercise Energy Consumption) is what happens after an intense training session. It's the calories you burn AFTER your workout (for up to 48 hours) because your body has been taxed during the training session and now it must recovery, repair and rebuild itself (bone density / muscle mass / glycogen stores / etc).
The harder you work, the more weight you throw around, and the more intensity that you use during training, the higher the EPOC effect. The watches are great but they only give you a small piece of information that can possibly be detrimental to your progress. It's amazing what a few pounds more or a little shorter break can do to your intensity and in-turn, what it can do to your body. Slight intensity increases can really change your body for the better. Next time you're in the gym tracking your calories, think about pressing the 20 pound dumbbells instead of the 15's, even if you get less reps, you're working harder. Instead of Goblet Squatting your normal 40 Pound Kettle Bell, try the 50 Pounder...Your body will be forced to adapt and change!