Why Feeling The Burn During Core Work Isn’t A Good Thing

That burn during crunches doesn't mean you are getting stronger or burning calories.

core workout

Adapted with permission of VeloPress from Core Envy: A 3-Step Guide to a Strong, Sexy Core by exercise physiologist and personal trainer Allison Westfahl. Learn more at

The term “burn” has been associated with exercise for a long time: Feel the burn, burn away fat, calorie burn, burning muscles . . . the list goes on and on. We all want to feel that the exercises we are doing are effective and worthwhile, and that burning sensation we get while doing a specific movement helps us feel that we are working hard, burning lots of calories, and therefore tightening the muscles that are burning. But what exactly is that burning sensation, and is it really a barometer for the effectiveness of a workout?

Contrary to popular belief, the burn that we feel in our muscles during exercise is not directly related to caloric burn or the amount of fat that is being burned. Just because you feel a burn in your abdominal muscles during a crunch, it does not mean that your body is burning fat in that area.

That sensation in your muscles is actually something else: an indication that those muscles are out of ATP, a cellular fuel your muscles burn for quick energy. That’s all it means. It doesn’t mean you’re burning a ton of calories; just that your muscles have burned all their stored ATP.

What you need to know for the purposes of fat loss is that the higher you get your heart rate, the more calories you will burn. It’s tempting to base the effectiveness of a workout on how much “burn” you feel in the muscles, but it’s the intensity and duration of the workout that will truly determine how many calories—and therefore how much fat—you are melting away.

Related: Tone Abs With This Crunch Free Core Workout


Most traditional core exercises are not scorching a lot of calories.

You can do crunches all day long and see no change to the fat you store around your midsection because your heart rate isn’t high enough, which means you aren’t burning calories at a significant rate. Again, it might feel as if you’re working hard because your ab muscles are burning and you can’t do more than 20 reps, but if you were to wear a heart rate monitor during crunches, it would show that your heart rate rarely gets above 90 beats per minute. When it comes to burning fat and losing weight, your heart rate is the prime indicator of success. It’s simple math: The higher your heart rate, the more calories you burn, and the more calories you burn, the more fat you lose. One pound of fat is equal to 3,500 calories, so you need to focus on exercises that will get your heart rate high enough to burn the maximum amount of calories in the shortest amount of time.

The higher your heart rate, the more calories you burn, and the more calories you burn, the more fat you lose.

How will you know which types of workouts are maximizing your fat loss? In 2005, the Journal of Sports Sciences published a study that outlined an equation to predict the number of calories burned per hour based on your average heart rate. We can apply this equation to different types of sculpting and cardio routines to determine which ones deliver the best results. As the oft-used adage goes: Don’t work harder, work smarter.

Core Envy by Allison Westfahl
Core Envy by Allison Westfahl

Let’s take the old crunches-based core routine as a starting point for caloric burn. If we assume an average heart rate of 90 beats per minute (which is the heart rate most of my clients exhibit while doing crunches), a 40-year-old female who weighs 160 pounds will burn approximately 195 calories in an hour. You could burn that many calories in 20 minutes by doing a moderate jog. Plus, when was the last time you did crunches for an hour? Most of us can last about 1 minute, which translates into 3.25 calories burned— that’s less than the calorie content of a breath mint. This is one of the myriad rea­sons why you won’t see standard crunches in my Core Envy sculpting routines. Instead, I’ve focused on exercises that recruit more of the muscles in the core, therefore burning off calories faster by elevating your heart rate. Keep in mind, however, that in order to truly maximize the fat burn around your belly, these sculpting workouts need to be paired with cardio. Sculpting routines alone cannot ensure optimal caloric burn.

Related: Why You Should Just Stop Doing Crunches