It sounds counterintuitive, but working out as hard as you can every time you exercise is, for most people, not actually the way to get the results you want. That’s because while high-intensity exercise is an efficient way to get a good workout, it’s physically taxing. After an intense workout, your body needs sufficient time to adapt to the stress it’s undergone. It’s during this period of recovery that your muscles repair and grow and your energy stores and fluids are replenished.
Of course there’s no one-size-fits-all intensity prescription; how hard you go will depend on your goals, the way you like to work out, how your body feels, etc. But exercise physiologist and host of the All About Fitness podcast Pete McCall, M.S., C.S.C.S., tells SELF that in general no more than two to three of your workouts each week should be high intensity. If you work out almost every day, make every third really hard, McCall suggests. The other days should be low or moderate intensity. “Exercise is stress on the body, and high-intensity exercise comes with greater stress loads,” McCall says. Mixing in lower-intensity workouts is important for giving your body the time it needs to repair and recover. Also, it’s important to note that it’s always best to talk with your doctor before ramping up the intensity of your workout routine.
But what is high intensity really and how do we know if we’re pushing ourselves enough? And what are low- or moderate-intensity, for that matter? It turns out there are a few ways to measure workout intensity and keep tabs on how hard you’re going as you exercise.
One way to do is this is by tracking your heart rate.
Generally, the higher your heart rate, the more you’re challenging your body. According to the CDC, moderate-intensity exercise is when your heart rate is at 50 to about 70 percent of your maximum heart rate, and vigorous-intensity exercise is when your heart rate is at 70 to about 85 percent of your maximum heart rate. But gathering all this heart rate info requires you to wear a gadget while you work out (like a chest strap, Apple Watch, Fitbit, etc.) and pay pretty close attention to it as you go. There’s also a classic formula you can use to for find your maximum heart rate (220 minus your age), but it has a large margin for error. The most precise way to measure it is in a lab, which, unless you’re an elite athlete, you probably don’t have regular access to.
The good news is that you can also judge intensity simply by keeping track of how you feel as you go, using a 1 to 10 scale that measures your rate of perceived exertion (or RPE, aka how hard you feel like you’re going at a given time). Gadgets are awesome and fun, but for the everyday exerciser, using the RPE scale is a more intuitive way to track intensity than using a HR monitor. Here’s why.
RPE is the most user-friendly way to measure workout intensity, because it’s based on a simple scale of 1 to 10.
The RPE scale was first created by Swedish psychologist Gunnar Borg in the 1960s. His scale actually went from 6 to 20, with 6 being resting and 20 being maximum effort. The idea was that multiplying your effort number by 10 would give you a HR estimate, McCall says. So if you feel like you’re working at a moderate intensity and rate it a 13 on a scale of 6 to 20, your heart rate is roughly around 130 beats per minute (BPM).
You’ve probably noticed the problem with this scale: Who actually rates things on a scale of 6 to 20? It’s not very intuitive, which is why Borg’s scale has since been modified to be a simple scale of 1 to 10. A 1 is basically sitting still, 2 to 4 is low-to-moderate intensity, 5 to 7 is moderate-to-hard, and 8 and higher is hard-to-intense. A 10 means you’re working at your maximum capacity, and you couldn’t possibly push yourself any harder.
Using the “talk test” is a great way to start to master the RPE scale.
One way to get a better grasp on what these numbers actually look and feel like for you is to use a talk test, PJ Stahl, C.S.C.S., co-owner and trainer at Lock Box in Los Angeles, tells SELF. When you can move and talk easily, you’re working at a low intensity (maybe a 1 to 3); when talking starts to require effort but is still sustainable, you’re in a moderate zone (about 3 to 5); when talking gets uncomfortable, you’re working at a high intensity (about a 5 to 7); and when it’s impossible to get out more than a word or two at a time, you’re approaching or at maximum intensity (about a 7 to 9, with 10 being so intense you can’t sustain it for more than a few seconds at a time). This highest intensity range is what McCall suggests you save for just a few days a week.
By using the talk test, you can get a better idea of how hard you’re working and more accurately rate your intensity level.
One thing to note about RPE is that it’s really subjective, which can be a plus or a minus.
Unlike measuring your heart rate, using RPE to determine your intensity is subjective—that means your perceived effort won’t always be an accurate representation of how hard your body’s actually working. “If you find a particular exercise uncomfortable, you will probably give it a higher RPE rating even if your effort is not equal to that tolerance level,” Stahl says. Plus, factors like whether or not you enjoy a workout, the temperature and humidity of the room you’re in, how well you tolerate discomfort, and more, can all influence how hard a workout feels to you on any given day. On the other hand, there might be days when you’re really tired or not fully recovered from a previous workout and you feel like you’re pushing yourself as hard as you can—maybe you’d rate your RPE as an 8 or 9—but a heart rate monitor would show you that you’re actually not going that hard, which might compel you to push yourself, even though your body is basically begging you to take it easy.
RPE can also be tough to judge accurately when you’re new to exercise. If you’re not familiar with different intensity levels and how they make you feel physically and mentally, then it’s hard to make an accurate assessment. The more exercise experience you have, the better you’ll be at understanding what certain levels of intensity feel like for you.
But when you’re trying to monitor your workouts on your own, RPE is usually the easiest way to do it.
Getting your max HR measured by a fancy machine and then using a heart rate monitor to stay in specific intensity zones throughout your workout is, of course, the most accurate way to do things. But that’s not realistic for most people, and, unless you’re a competitive athlete, that added accuracy probably won’t make a huge difference in your training.
So while RPE wouldn’t pass muster in a laboratory, it’s the most accessible and “least invasive” way of monitoring intensity, says Stahl. It’s also just never a bad idea to get more in tune with your body and understand how it’s feeling—that’s a skill that you’ll be able to use the rest of your life.