I've recently been asked about heart rate monitors and the reasons. This article from BeachBody (P90X programs, etc.) explains more.
Why You Should Wear a Heart Rate Monitor
By Steve Edwards Your heart is the most important muscle in your body. It delivers oxygenated blood from your lungs to the rest of your body and, as you're aware, oxygen is the primary ingredient keeping us alive. Like any muscle, the heart needs to be exercised, and monitoring your heart rate is an easy way to keep yourself working in the right "zone," reducing your chance of injury and overtraining, and increasing the odds that you'll get the results you want.
Heart rate monitors measure your cardiovascular and physiological stress during training sessions. They provide you with an accurate gauge of how intensely you're exercising, which is reflected in your heart rate. The harder you exercise, the higher the heart rate goes. When your heart rate changes, it's a sign that something is happening. By monitoring your heart rate, you will learn to tell when your workouts are effective, when you are over or undertraining, and even when you may be getting sick and need to back off
How Do I Understand My Heart Rate Monitor?
These days, heart rate monitors come in many shapes and sizes. Some simply show your heart rate, time of day, and offer a stopwatch function. Others measure the wattage you're pushing on your bike, count every step you take, and map and measure every place you go. Provided you learn to use these features, they all have potential to help you get fitter. Today we'll stick to the heart rate portion, which simply counts the number of times your heart beats.
Heart rates are measured in beats per minute (bpm). Your resting heart rate indicates your basic fitness level and is defined by the number of times your heart beats per minute while your body is at rest. In general, the fitter you are the less effort, and fewer beats per minute, it takes your heart to pump blood to your body at rest. I say in general because part of this is genetic. We're born with varying genetic capacities for this process, so you should measure your heart rate versus your own and not someone else's because you could be fitter than someone who has a naturally lower heart rate.
To gauge this, measure your resting heart rate immediately after waking up and before you get out of bed (so, yes, wear your monitor to bed until you understand the process—you can also count your pulse but it's less accurate). Take these measurements for five consecutive days and find the average. This average is your actual resting heart rate. Resting heart rate is dependent upon your living habits and a number of factors such as your quality of sleep, stress level, and eating habits.
Your average heart rate is the number of times your heart beats within a certain period of time, like over the course of a workout.
Your maximum heart rate (max HR) is the maximum number of times your heart can contract in one minute. An accurate max HR should be tested in a lab setting. In lieu of lab testing, we use this formula:
Women: 226 – your age = your age-adjusted max HR
Men: 220 – your age = your age-adjusted max HR
For example: If you are a 30-year-old woman, your age-adjusted maximum heart rate is 226 – 30 years = 196 bpm.
These formulas apply only to adults and have an error margin of +/–10 to 15 beats per minute, due to different inherited characteristics and exercise training. If you want to exercise/train at your most effective levels, your max HR should be measured. However, most of us are fine using the above estimates. When you need your training to be more specific, you'll almost certainly know it because you'll be obsessing over a race or event as opposed to simply trying to be healthy.
Your anaerobic threshold (AT) is the physiological point during exercise at which your muscles start using up more oxygen than the body can transport (the point where lactic acid accumulates and you get "pumped"), which forces you to stop. This point becomes obvious without any monitoring. It's why you can't do push-ups forever and why people drop to the floor during sets in INSANITY®. While you can't control it, you can train it if you know where it is, which you can figure out using your HR monitor.
Note: Like your max HR, your anaerobic threshold doesn't necessarily correspond to others. Some people have naturally higher maximum heart rates than others.
What's a Heart Rate Zone? And What Zone Should I Be in?
These "zones" correlate to different levels in intensity, which (as you'll see below) increases as you get closer to your max HR. In any hard workout you will experience all of them. Easier workouts will skip the higher zones.
| Heart Rate Zone | Percentage of Max HR | Perceived Exertion Difficulty |
| Z1 Healthy Heart Zone | 50%–60% | 2–5 (perceived exertion) |
| Z2 Temperate Zone | 60%–70% | 4–5 (perceived exertion) |
| Z3 Aerobic Zone | 70%–80% | 5–7 (perceived exertion) |
| Z4 Threshold Zone | 80%–90% | 7–9 (perceived exertion) |
| Z5 Redline Zone | 90%–100% | 9–10 (perceived exertion) |
In the lower zones—sometimes called "cruise zones"—you can train for longer periods of time. As you move up to higher-intensity zones, you need to decrease the amount of time that you spend in these, particularly in the top two (the Threshold and Redline Zones) where your body, as noted above, will make you stop.
Your five heart rate zones are specific to your maximum heart rate, not anybody else's. For example, if there two runners are each maintaining a heart rate of 160 bpm, one runner might be in their Z4 Threshold Zone while the other might be in their Z2 Temperate Zone.
Each heart rate zone burns a different number of calories per minute. How many calories you burn within the range for each zone depends on how fit you are:
Zone 1 = 3–7 calories per minute
Zone 2 = 7–12 calories per minute
Zone 3 = 12–17 calories per minute
Zone 4 = 17–20 calories per minute
Zone 5 = 20+ calories per minute
Looking at this, you all probably want to be in zone 5 as much as possible. Unfortunately, the time we can spend here is limited. For efficiency, Beachbody® workouts try and maximize the time spent in the higher zones, which we'll get to in a moment. Training in the lower zones is also important.
What About the "Fat-Burning Zone"?
The Fat-Burning Zone. You'll notice the lack of something called the fat-burning zone in the table below. The reason for this is that it's misleading because people feel the need to stay in this low heart rate zone in order to burn fat. In reality, the opposite is true.
In Z1 and Z2, you're using stored fat for fuel. It's cool-sounding, yes, but your body is doing this because it's trying to conserve its limited stores of something called glycogen, its primary fuel for hard exertions. It's important to train in Z1 and Z2, but most of us train in it plenty during our warm-ups, cooldowns, recovery periods between hard sets of exercise, and the daily activities in our life. Endurance athletes, however, do need to spend extra time training these zones because their sport requires it. In theory, you'll never get tired because your heart can continue to pump oxygenated blood to your muscles indefinitely. In reality, we still break down and wear out—like the way you feel after a long day at the mall—so those who compete for many hours need to spend more time training "long."
Z3 is called aerobic because it's the hardest zone you can train in without going anaerobic (the point where the pump starts settling in). This is what we're targeting in steady state "cardio" workouts. It's actually quite hard to stay in this zone because we're always creeping into zone 4, so the most effective way to train it is using an over/under strategy, which is done by training in intervals between the higher and lower zones. Again, endurance athletes often try and target this zone more specifically because their sport requires that they maintain as fast a pace as possible without getting pumped.
Z4 and Z5 are your anaerobic zones. You can't stay in these very long because your heart can't pump oxygen to your body fast enough. Your body is using glycogen (via blood sugar) as fuel and it runs out rapidly—part of why Results and Recovery Formula® works so well after hard workouts where you've spent a lot of time in these zones. Trying in these zones forces your body to break down muscle tissue and fire "emergency" hormones to repair this tissue, which is all vital for getting fitter (and looking "ripped"). All athletes, even endurance athletes, spend most of their training focused in this area.
What Zone Should I Be in During My Workout?
As you can probably guess, you want to do each Beachbody workout to the maximum of your ability. This means that you don't back off so that your heart rate falls into a lower zone on purpose, as you might if you were training for a triathlon.
The only exception is if you're following a "doubles" routine, where one of your two workouts is supposed to be at "low to moderate intensity," meaning that you don't want to exceed Z2. But our programs are based on efficiency, and in most cases, intensity = efficiency.
To get a sense of how intense you're working out, your heart rate monitor is a great tool to help you monitor and track your progress, and make sure you are working hard enough to get the cardiovascular and fat-burning results you want.
In general, you should see a pattern throughout the course of any Beachbody program. "Cardio" days will burn more calories than resistance days at first because you're moving more and your average heart rate is higher. Over time, however, you should get stronger and, thus, lift more weight for more repetitions in resistance days, greatly increasing the caloric burn for those days. This is why so many of our programs use weight and, even in INSANITY (which uses gravity in place of weight), we add weight to the later workouts of ASYLUM. If this is not happening, it means you need to add weight and/or repetitions to your resistance workouts! Besides what you see in the mirror, this is best way to see if you're making improvements in your health and fitness.
You will also learn that by tracking your progress, you'll be more in tune with external factors that are upsetting you. You will be able to tell when you are getting sick or overtraining. When that's happening, you won't be able to get your heart rate to maximums that you've seen prior, or your heart rate at rest will be too high. This is an indicator that something isn't quite right.
The best way to stay ahead of the game is by getting into the habit of checking your resting heart rate each morning before you get out of bed. As you get into shape, it should continually drop. If it reverses this pattern for more than a couple of days in a row, it's telling you that your body is stressed, which could be due to overtraining, the onset of an illness, or some other negative environmental impact. In any case, that means it's time to back off until your resting heart rate goes back down. If wearing your monitor to bed is too much trouble, just use your fingers and count beats of your pulse at your neck or wrist for a minute. It's less accurate, but you don't need to be perfect. A racing pulse means something is amiss (though your pulse will be fast for the first couple of weeks as you adjust to any new program).
Once you learn your body's patterns, you'll be able to anticipate your body's needs rather than just reacting to them, and this alone justifies learning your way around a heart rate monitor at least once in your life.
