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Does It Really Matter How Many Calories Your Workout Burns? [The problem with heart rate monitors]

Posted May 08 2013 1:33am


This “super slimmer” face mask from japan claims to burn calories (from your face?!) while you sleep. That is, if you can sleep in something that looks like the brainchild of Hannibal Lecter and a Mary Kay salesman.

You’ve seen the workout program ads: in between shots of glistening, contracting abdominals and hyper smiling people who only sweat in socially acceptable places (your amped up cleavage if you are a woman, your shaved pecs if you are a man) comes The Promise. What, you ask, can a DVD workout/exercise book/smiling B-list celeb promise me when it comes to cardio other than a perfect body, chiclet teeth and a spray tan so authentic that real sunshine is jealous? Why, the promise of an amazing ultra-high superbad caloric burn of course!

I was reminded of this the other day as the Gym Buddies and I were sweating away on the elliptical machines (not our go-to workout but they’re easy to talk on so sometimes we end up there) and one of those ubiquitous exercise program infomercials came on. While we were giggling about watching people on TV exercise while actually exercising, large letters flashed up on the screen. “BURN up to 1,000 CALORIES AN HOUR!” flashed over all those heaving chests – the “up to” in conveniently small type of course.

This infomercial – may Billy Mays rest in peace – is not unique. All fitness programs, televised and otherwise, seem to make some kind of caloric promise. Not to mention the charts in every fitness mag and diet book showing you how many calories everything from Zumba to sex burns. But how accurate are these claims? And does it even matter how many calories your workout burns?

Q: Can You Really Burn 1,000 Calories An Hour?

Anecdotal evidence first: According to my overly generous heart rate monitor of which I was once so attached to that I would turn around and go home to get the chest strap if I accidentally forgot it despite the fact that being small chested meant that it looked as if I had a 3rd nipple, I have burned over 1,000 calories in a single workout. The scene was “Holiday Turbokick” a special brand of torture that Turbo Jennie likes to put us through on occasions like the day before Easter, where we do 8 “turbos” (a high-intensity interval lasting between 30 seconds and 2 minutes) interspersed with 4 finales or some such craziness. By the end I am turbo-ing in a puddle of my own filth and can wring out my top like a Shamwow. It’s enough to make a girl puke up her turkey before she even eats it, is what I’m saying. But by the time we hit cool down, I had indeed burned just over 1,000 calories.

So it would seem possible – although unlikely (who wants to work out so hard you vomit every day?) – to attain that magic number. Except for two problems. 1) My heart rate monitor wasn’t terribly accurate. While I trusted its ability to read my actual beats per minute, its calorie burn function was apparently calculated based off a 6’6″ male Russian ice swimmer. To prove this, I switched heart rate monitors with Gym Buddy Allison, who wears a different brand, and racked up 200-400 less calories per hour than my watch gave me.

2) Even the venerable Polar or Garmin can’t really tell you your caloric burn as metabolism is so individual as to render any mathematical formula at least slightly inaccurate. The research in this area is more prolific than one might think. Companies that make a living off of guaranteeing a good workout have invested a lot of energy into trying to figure out what number of calories people can expect to expend using their machines or programs. What they have discovered however is that while they can predict how many calories an individual, say Michael Phelps, is burning, those results are very difficult to generalize. In addition to individual metabolisms there are simply too many other variables. Therefore, the honest companies will give you a range of calories. The disingenuous ones will use that sneaky little phrase “up to” and then give you a Michael Phelpsian number just to make you feel good.

3) Don’t even get me started on how inaccurate the calorie-burn calculators on the cardio machines are.

Q: Does it Matter How Many Calories You Burn?

Every fitness expert will tell you that weight loss, gain or maintenance comes down to simple math. It’s all about the calories you take in through food in relation to those you expend through daily life and exercise. This over simplified heuristic often leads people to think things like, “If the treadmill says I burned 250 calories, then that means I can eat a 200 calorie muffin and still come out losing!” This, in turn, has made calorie burn the gold standard in assessing a fitness program’s worth.

But dig a little deeper and you will realize that not only is calorie burn not the best indicator of a workout’s power, it actually distracts you from other benefits of exercise. For instance, weight lifting typically doesn’t burn comparatively as many calories as cardio for the same amount of time and yet it has many advantages like increased strength, muscle mass and overall functionality. Similarly, HIIT (high intensity interval training) burns a smaller amount of calories during the actual workout but causes a much greater spike in HGH (human growth hormone) than twice the amount of traditional medium-intensity cardio. Lastly, cardio exercise is good for many things besides just burning off last night’s dessert – like increasing your oxygen utilization, building endurance and even improving your mood.

Q: Is It Even A Good Thing To Burn 1,000 Calories An Hour?

Confession: Back in our heart-rate monitor days, Gym Buddy Allison and I were so fixated on burning a certain number of calories per workout that if we hadn’t met our quota, we’d literally do jumping jacks in place while waiting to pick up our kids until our monitors showed the “magic” number. Ignoring for a moment how dumb we looked doing that (and the fact that I was a chronic over-exerciser and very sick at that point), one must ask if it is even a worthwhile fitness goal to strive to burn a particular high number of calories. To get that kind of calorie burn, we would have to push very hard in a high intensity type of cardio. Much has been said – and ignored – about the dangers of too much aerobic exercise in the highest heart rate zones. It elevates the stress hormone cortisol, causes systemic inflammation, necesitates longer recovery and increases your risk of injury, just to give you the short version.

In addition, an often overlooked fact by dieters and diet purveyors alike is that  the more you exercise, the hungrier you get . From my personal experience the more calories I burn, the more my body wants to replace them – and fast. What’s the quickest source of glycogen for our depleted muscular system? Sugar. I have found that after a long training run, it’s almost impossible for me to stay away from the Swedish Fish and other simple carbs for the rest of the day. However, when I strength train and/or keep my training volume low my sugar cravings diminish significantly (unless I’m PMSing but that’s a different story entirely).  Research backs me up  by showing that dieters who create a calorie deficit purely from exercise don’t lose weight – because their bodies eat to adjust. So, what’s the point in burning (up to) 1,000 calories if my body is immediately going to want to replace (at least) 1,000 calories with whatever food is easiest for me to scarf down?

Q: Do You Need a Heart Rate Monitor?

Most people I know that have a heart rate monitor were talked into getting one either by their personal trainer or a gym promotion. (Side note: Most people I know that have a heart monitor say programming the dang thing is on par with reading the tax code… in Hungarian.) Considering they’re pricey little pieces of equipment, you need to consider it’s utility before you buy. There are two main reasons to use one:

The first is “zone training” with the theory being that since you burn a higher proportion of carbs to fat at higher intensities of exercise then having preset zones will help you maximize your fat burning by keeping your heart rate from getting too high (burning straight sugar) or staying too low (burning fat but at a very slow rate). Different types of workouts are designed to take you through various zones and it can be hard to know which zone you’re in if you don’t have a monitor.

The second reason is usually calorie tracking. The watch provides a more reliable and customizable number than guessing from a website.

Okay, there is a third reason. You just like the way it looks! It makes some people feel hardcore or show that they’re “serious” about their workouts. Or they just really like the third-nipple look.

So do you need one to get a good workout? No. Are they sometimes useful to have? Yes.

Q: What do I do? 

Honestly, calorie burn doesn’t matter much to me anymore.  I haven’t worn a heart rate monitor in over two years and don’t miss it a bit. My main measure these days of a good workout is the fun measure. Granted, I’ve been exercising long enough to know what it feels like for me to be at “maximal effort” or “90% of my max heart rate” or even what my aerobic threshold (AT) feels like. I can see how wearing a monitor could help someone new to fitness learn to recognize how hard to push yourself (hint: it’s always harder than you think). But for me it ended up just being one more number for me to obsess over so just like I no longer count calories, weigh myself, or even measure my body fat percentage, I also don’t worry about my calorie burn. Call it intuitive exercising, if you will.

All of which is not to say that exercise – even an occasional session of long, intense cardio – shouldn’t be done. Ask any triathlete, marathon runner or Iron(wo)man if their race was worth it and most of them will give you an enthusiastic yes. But it isn’t because they burned 3,000 calories, it’s because they were having fun and it gave them a sense of accomplishment. Does it mean that I don’t get a great workout from Holiday Turbokick if I don’t burn quadruple-digit calories? No! I’m still increasing my endurance and having a lot of fun to boot. I’m not even saying that you shouldn’t measure your calories burned – you may find it motivating, educational or just entertaining. My long-winded point: When we are evaluating the merit of a particular fitness program, there are a lot of better factors to consider than supposed maximum calorie burn.

Do you have a favorite fitness infomercial? Anyone else ever been obsessed with burning a certain number of calories during your workout? Do you wear a heart rate monitor?

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