All right, your heart rate monitor has arrived, you’ve become a card-carrying member of the Fitbit crowd, and you’ve bragged about it to all your friends, colleagues and random people you’ve met on the train.

Now, there’s only one problem. What exactly are you supposed to do with the silly little thing?

The rationale of exercising with a heart rate monitor is that this helps you to train more scientifically. It makes it possible to see the effect of exercise on your body instead of relying on performance outcomes.

It’s not always easy, though, to tell whether you’re getting stronger and faster or just more motivated. Are you just going through the motions, or are you perhaps pushing yourself too hard?

Knowledge Is Power

Did you know that there are now electric toothbrushes that can tell you how well you’re cleaning your mouth? You don’t need to wait for your dentist to discover a problem: if you’re not doing all you should in that area, you can correct your habits before something bad happens.

It’s therefore important to know whether you’re on the right track while you are still, so to speak, running it. Otherwise, you may end up wasting months overtraining, undertraining, or working out in a way that doesn’t really support your fitness goals.

The key to working out effectively is to track your calorie consumption and, as will be explained below, keep it in the Goldilocks range.

How do you measure calorie consumption?

Your heart rate is the closest analogy. Keeping an eye on this will also prevent you from placing too much strain on your body and, you know, keeling over.

Introducing the Fat-Burning Cardio Zone

Though it’s not the only way to lose fat, maintaining an elevated heart rate for an extended period of time is one of the most effective methods of activating your body’s calorie-burning machine.

So, logically, working out as hard as you can and keeping it up until you drop should be the way to build lean muscle and boost your cardiovascular health, right?

Nope, the human body isn’t that simple.

It’s tempting to think of everything solely in terms of calories in and calories out. In general, things do average out that way, but take a moment to consider where those calories you burn come from:

• The muscles themselves. Each muscle cell has a small amount of glycogen – a kind of carbohydrate – available for immediate use.
• The liver. Aside from making your hangovers less severe, the liver also stores glycogen, ready to release it into the bloodstream as needed.
• Fat. If you’re interested in using a heart rate monitor for exercise, we’re going to assume you already know what fat is.

Now, glycogen is fast energy. Immediately available but not all that plentiful. With fast-twitch muscle fibers (those that are strong but lack endurance), a single major effort may leave them exhausted.

Fat is slow energy: there’s a lot of it, but it takes time to get where it’s needed.

Using a Heart Rate Monitor for Weight Loss

If you use your limited store of carbohydrate energy too quickly, you’ll be exhausted and your workout will be over prematurely.

These calories will eventually be restored from fat, but you’ll have all the get-up-and-go of a sack of potatoes the next day and may well end up overeating. At least as part of a long-term weight loss plan, this is far from ideal.

If, naturally, your heart rate is too low during your workout, you’re not using many calories of either kind and won’t lose weight no matter what.

How does a heart rate monitor tell you whether you’re sweating enough but not too much?

A good guideline uses your maximum heart rate as a baseline (which is very different from your resting heart rate).

For example, a forty-year-old will have an MHR of 180.

If you’re fairly out of shape or just getting started with working out, it’s probably a good idea to be conservative and choose a somewhat lower number.

Then, use the following chart to guess at how much fat you’re shedding at any particular level, assuming that you exercise at that pace for at least 15 minutes:

Pursuing Peak Fitness with a Heart Rate Monitor

Long before fitness trackers with heart rate monitors became as cheap as they are today, they were used by sports scientists and professional athletes as a training aid. At their level, there’s a fine line between not pushing hard enough to gain that vital extra particle of performance, and overtraining and actually losing ground.

In this case, your heart rate while exercising is really a stand-in measurement for how much oxygen your body is consuming. Depending on what level of endurance you hope to achieve, you may want to use your heart rate monitor to exercise at 70% to 80% of your maximum heart rate for extended periods of time, thus strengthening and conditioning your heart muscle for when it really matters.

With digital heart rate monitors, you don’t have to remember to take a note of this number. You can review all the data on your computer or mobile device and track your performance over time, which by itself can be a great motivator.

So, Do You Need a Heart Rate Monitor?

Nobody needs a heart rate monitor to train effectively. If all you’re interested in is improving your health and fitness in general, doing any exercise at all is already a good starting point.

It’s worth mentioning, however, that modern fitness trackers are meant to be worn throughout the day and monitor how active you are in general, encouraging you to walk or take the stairs more often. Small changes like these can have significant results.

Like a massage gun or a home treadmill, a heart rate monitor is just a tool. It remains your responsibility to actually get out there and exercise.

What it can help you with is working out more efficiently by letting you know how close you are to your goals. Tracking your progress by lap times or reps is fine, but considering that most fitness trackers cost less than a year’s gym membership or a new pair of running shoes, isn’t it worth taking a look under the hood?