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How Important Is Heart Rate to the Quality of My Workout?

I’m hoping all of that huffing and puffing adds up to something. Otherwise, I’m totally screwed

Given the frequency with which I engaged in discussions with personal training clients about cardiovascular strategies — from their variety, to their intensity, to their duration — it’s amazing that heart rate never came up as a topic of conversation. In fact, the only time heart rate was ever formally introduced into any of my own training was during swim practice, when my coach would ask me to check my pulse rate for six seconds after some of our most savage training sets, which I was then to report back to him. Usually, he’d just nod and say, “Good.” 

I now know that he was multiplying that number by 10, and determining whether or not it fell within an acceptable range of difficulty for whatever he had intended the set to accomplish. Otherwise, I just associated a sky-high heart rate with considerable physical discomfort and a telltale sign of being out-of-shape.

How important is heart rate to tracking the success of a workout?

I suppose it depends on who you ask. But most fitness experts who care about training heart rates enough to track them usually place them within five color-coded zones of effort: gray, blue, green, orange and red. 

The gray zone would include exercise that most people wouldn’t even regard as exercise — e.g., a casual two-block walk to grab beer from the 7-Eleven. Sticking with that analogy, if you knew that you had about 10 minutes to get there and back before you missed the beginning of the second half of the football game, you might pick up the pace, but not quite to the extent that you’d be jogging. This would probably place you in the blue zone.

Once you enter the green zone, you’re in an area where obvious work is being performed, and things might become less than comfortable. Essentially, when you call your friend to let him know that you’re jogging back as quickly as you can, he’s going to notice that you’re clearly breathing hard. As you enter the orange zone, it’s probably not even worth calling him with any updates, because verbal communication is gonna be less and less discernible.

If your return from the store is a red-zone effort, this means you’re in a dead sprint, likely doing nothing but huffing and puffing.

Yeah, yeah, I get it — gray, yellow, purple, yadda, yadda. Again, though, how important is my heart rate?

It’s definitely more important than not if you’re a competitive athlete. Because if your sport requires any sort of sustained effort beyond what would be asked of a golfer or a bowler, you’ll probably be considered a liability if you don’t spend at least some time training in the uppermost heart-rate zones. Almost every sport is going to require you to sprint at some point, and your ability to sustain your sprinting speed for as long as possible — and also recover from those efforts quickly so that they can be replicated — is crucial. 

Honestly, though, outside of a context where you have a precise athletic goal in mind, there isn’t a compelling reason why you need to train within the two most demanding heart-rate ranges. 

But don’t I burn more fat if I train in specific zones?

I understand why you might believe this. After all, such claims have been printed directly on many cardio machines for decades. But there are some inherent lapses in logic whenever this principle is applied.

Whether your body is burning inbound food or body fat during your training is practically irrelevant; unburned calories are stored as body fat, period, and if there’s a shortage of new food to burn as energy, the body will ordinarily burn its stored fat. Basically, if you eat a slice of cheesecake and then commence an intense stepmill workout, and you’re somehow able to burn off 400 calories of broken-down body fat over the course of the subsequent hour by locking yourself into the optimal heart-rate zone, any unused calories of that cheesecake are still going to replenish the burned body fat — and then some. 

What I’m saying is, it will make no difference what type of calorie was burned during a cardio session unless a caloric deficit is created in the process. When that occurs, it will result in a net decrease in body fat. When it doesn’t, more body fat is ultimately created.

Okay, but do I burn more calories even when I’m not working out if I keep my heart rate high during training?

What you’re talking about is the concept of “afterburn” and excess post-exercise oxygen consumption (EPOC). But if I were you, I wouldn’t bet my body on it, because the studies used to support afterburn and EPOC don’t uphold as neatly as some people would hope.

One of the studies cited to support the idea of afterburn demonstrated that a one-set resistance-training regimen at higher intensity resulted in similar resting energy expenditure to people who completed three resistance sets for individuals identified as “overweight.” But the takeaway should be that resistance training might be an attractive alternative to aerobic training for overweight individuals in need of weight loss, not that training at a specific heart rate for a shorter period of time should enable you to skip workouts.

A more relevant study found that individuals who trained at high intensity for 45 straight minutes burned an additional 190 calories over the next 14 hours of their day. However, 45 minutes is a significant amount of time for a cardiovascular training session, and many of those additional 190 calories can also be burned by extending the workout by an additional 15 minutes and training at a lower intensity throughout.

It sounds like you’re saying I shouldn’t pay attention to my heart rate.

What I’m suggesting is that you shouldn’t attempt to use your heart rate as a tool to hack your training results. If you fall into the category occupied by most non-athletes, it would be wise to think of your heart rate as an indicator that you’re either training too hard, or not hard enough. It’s far more important to fill a prescribed hour of training time with sufficient motion every day of the week as opposed to participating in a training session that lands your heart rate in the orange zone for 15 minutes only once a week.

In other words, you want to follow whatever color consistency is.