Thanks to smartwatches and fitness applications that monitor virtually every health metric, it’s simple to become preoccupied with the numbers — and overlook paying attention to how you feel — while you exercise. One easy way you can keep track of your body? Refer to the rating of perceived exertion, or RPE, scale, which focuses on physical sensations that may arise during physical activity and informs you about the intensity of your workout.

Here, trainers break down the definition of RPE, share a standard RPE scale and its advantages and drawbacks, and provide recommendations on how to utilize the tool to your benefit.

What Is RPE?

Simply put, the rating of perceived exertion is a tool used to gauge the intensity of your workout or physical activity by tuning into your body, says Katie Fogelson, a MIRROR trainer and lululemon ambassador. Instead of relying on definitive metrics, RPE is based on how strenuous you feel your body is working, taking into consideration physical sensations such as elevated heart rate, breathing rate, perspiration, and muscle fatigue, according to the Centers for Disease Control and Prevention.

Although there are various RPE scales used to measure the level of effort, the most commonly utilized scale is a range from 1 to 10, says Fogelson. Below, the trainer provides an explanation of what each rating signifies.

RPE Scale

• RPE 1 to 3: Low intensity. You can converse normally, breathe naturally, and overall feel comfortable.
• RPE 4 to 6: Moderate intensity. You can speak in short bursts, your breathing is more labored, but you’re still operating within your comfort zone.
• RPE 7 to 9: High intensity. You can hardly speak, you’re breathing heavily, and you’re pushing beyond your comfort zone.
• RPE 10: Maximum effort intensity. You cannot speak, you’re gasping for breath, and you’re working at your physical limit or beyond it.

The Advantages of RPE

The RPE scale may be uncomplicated, but it should not be underestimated. Firstly, it can serve as a straightforward method to ensure you achieve your weekly goal of 150 minutes of moderate-intensity activity or 75 minutes of vigorous-intensity activity, as recommended by the U.S. Department of Health and Human Services. Specifically, you will meet your moderate-intensity targets when your RPE is a five or six, and you will fulfill your vigorous-intensity targets when your rating of perceived exertion is seven or eight, according to the D.H.H.S.

More importantly, determining your rating of perceived exertion (RPE) can help you avoid burnout early on in your workout session, says Morit Summers, a certified personal trainer and the owner of Form Fitness Brooklyn in New York City. “If my workout is 60 minutes, I can’t give a hundred percent, get to that RPE of 10 within the first 10 minutes of my workout — then I’ve already given everything that I have and I can’t get through the rest,” she explains. “When I have this hour workout, I want to be able to stick anywhere from a six to an eight most of the time.” By staying within that RPE range, you’ll work up a serious sweat and feel challenged, but you’re still able to finish the entire workout without feeling like you’re dying, she says.

RPE also focuses on how you’re feeling — not your heart rate, breathing rate, or pace, says Fogelson. Without the pressure of your fitness tracker metrics, you might feel more comfortable dialing back your workouts if your body is telling you to do so. “RPE’s fluid approach to training intensity makes it easy to shift gears and keep pushing in the gym without being stuck to a rigid system,” she says. “…No matter how fancy your fitness tracking device may be, it can’t tell you how you feel.”

The Limitations of RPE

The foundation of rating of perceived exertion is understanding how you’re feeling in the moment. The problem? Many individuals struggle to pinpoint just that, which can reduce the tool’s accuracy, says Summers. “Some people don’t realize how hard they go right off the bat…then other people are almost too nice to themselves and will be in the three-to-four range for the whole time,” she explains. “If you are trying to work out harder or make progress in some way, you’re going to need to push that RPE a little bit.”

The tendency to overestimate exertion level is particularly common among fitness newbies and intermediate exercisers, and connecting with your body in this manner isn’t a quick process, adds Fogelson. “Getting to know your RPE can take some time if you’re a beginner and/or new to exercise in general,” she explains. “Learning how to tune into your body is a skill that will improve over time and, as a result, so will your ability to determine the correct RPE.”

Due to those potential drawbacks, Summers suggests viewing RPE simply as another tool to have in your pocket — not the only way to gauge your workout intensity. While lifting weights, you can also determine your exertion level by considering how many reps you’re able to power through in a set compared to your goal. Say you pick up a set of dumbbells and are aiming to complete 10 reps of bicep curls. If you end up doing 25 reps without feeling too fatigued, your RPE might be a 3 and you could benefit from increasing that weight, says Summers.

Similarly, percentage training — determining load based on your true or estimated one-rep max — can clue you in on your intensity while pumping iron, adds Fogelson.

For instance, if your maximum weight you can lift in a deadlift exercise (which is equivalent to 100% of your effort, or a rating of how hard you perceive it to be of 10) is 100 pounds, then a deadlift at 70 pounds would require 70% of your effort level (with a rating of perceived exertion of 7).

“While the rating of perceived exertion (RPE) is more widely understood and accessible, it is also subjective in nature, which inherently makes it less precise,” she clarifies. “Training based on percentages eliminates the need for guesswork and allows you to measure progress using very precise metrics.

During cardio-focused workouts, you can refer to your heart rate to determine your level of effort, says Fogelson. For moderate-intensity physical activity, your desired heart rate should be between 64 percent and 76 percent of your maximum heart rate. For vigorous-intensity physical activity, it should be between 77 percent and 93 percent of your maximum heart rate, according to the CDC. Your heart rate is often easily measurable and quantifiable (thanks, smart watches) and generally aligns well with your rating of perceived exertion (RPE), says Fogelson. However, “less physically fit athletes tend to have higher resting heart rates, and their heart rate increases more quickly, which doesn’t always correlate with their RPE,” she explains. “The more physically fit the athlete, the closer the correlation between heart rate and RPE”.

TL;DR: There’s no single best way to measure the intensity of your workout, so find a tool or two that works most effectively and accurately for you.

How to Utilize RPE During Exercise

Ready to give the RPE tool a try? Begin by using it as a general guideline to adjust the intensity of your workout. “Generally speaking, during exercise, we want to push ourselves a bit, feel slightly out of breath, sweaty, and engage our muscles, so we should be at a five to eight on the RPE scale,” says Summers. “If you feel like you’re below that range, you could probably increase the intensity a bit”.

However, the specific rating of perceived exertion you aim for will depend on your fitness goals, says Fogelson. “If your goal is to enhance endurance for long-distance runs, you’ll spend more of your workout time in lower RPE ranges,” she explains. “But if you’re training for speed or sprinting-based runs, there will likely be a mix of high-intensity or high-RPE workouts”.

In the latter cases, it’s important to be strategic about when you hit an RPE of 10. If you’re completing 10 30-second sprints, hold off on reaching that perceived exertion rating of 10 until your eighth or ninth sprint, says Summers. “If I start at maximum effort, I won’t be able to complete the rest of the sprints,” she explains. While HIIT workouts often involve short bursts of high-RPE exercises, make sure you save your all-out, level 10 effort for the end of the session, ensuring that you’re able to finish without feeling completely exhausted right from the start, says Summers.

To ensure you’re staying on track with your target RPE, have a plan in place for how often you’ll check in with yourself during your workout — and stick to it. Consider assessing how you’re feeling after every mile during a run, between each circuit of a HIIT workout, or after every set while weightlifting, suggests Summers.

And remember, “if you’re new to RPE training, give it some time,” says Fogelson.

And attempt to rehearse without utilizing any gadgets, so you can genuinely synchronize with your body and aren’t influenced by what you’re observing on your timepiece.