The Single Most Important Fitness Metric You Aren't Tracking but Definitely Should

This one marker is more important than anything your smartwatch tells you

Photo by Alonso Reyes on Unsplash.

What if there was a way to wake up and know exactly what your body needs to feel its best? A way to determine whether you should go to CrossFit class or opt for a leisurely walk; a way to know if hitting snooze will actually be better for you than your regularly scheduled morning workout?

Good news. There is a (totally free and easy) tool to answer those sorts of questions: It’s called the ratings of perceived exertion (RPE) scale. 

The RPE scale isn’t totally preemptive, but it certainly has the power to help you adjust the intensity of your daily workouts to best suit your body’s needs. 

I like to call RPE the “analog version of Whoop,” because it’s really all you need to know if you should tone things down a notch — or if your body is ready for an extra challenge. Tools like Whoop are valuable and helpful, but if you’re in tune enough with your body, you don’t need them.

Ahead, learn how to accurately measure RPE and how to use it to improve your workouts.

What does RPE mean?

RPE is an effort rating scale for workouts. Photo by Danielle Cerullo on Unsplash.

RPE stands for “ratings of perceived exertion.” It’s a way to measure how your body responds to a workout and to monitor how hard you’re working during exercise. RPE is measured on a scale — aptly named the RPE scale — and it can help you determine whether you’re pushing yourself too hard or not hard enough. 

Learn more: What does tempo mean in workouts?

How to measure perceived exertion

You can measure perceived exertion in one of two ways: Use the Borg scale or the modified scale. Learn the difference between the two RPE scales in this section.

Borg scale
​The Borg scale ranges from six to 20 and is the original and preferred way to measure perceived exertion. Swedish professor Gunnar Borg first introduced the concept of RPE in the 1960s. He later published the scale in the journal Medicine and Science in Sport and Exercise as a basis for “psychophysical” estimates for exertion. 

If you’re wondering why the Borg scale starts at six and goes to 20, the logic is actually pretty simple: This scale is designed to make it easy to estimate your heart rate while exercising. All you do is multiple your Borg RPE by 10 to get an estimated heart rate. 

For instance, if you’re just sitting on the couch, you’d rate the activity a six (we hope). Multiply that by 10 and you’ve got 60, a fairly average resting heart rate for healthy people. If you’re doing a workout and rate it a 15, you can estimate your heart rate to be 150 beats per minute, which equates to hard or vigorous activity.

The Borg scale of perceived exertion.

Simple RPE scale
​“On a scale of one to 10, tell me how bad it hurts.” 

That’s basically how the simple RPE scale works. This scale ranges from one to 10, and you rate the difficulty of the workout based on how hard it feels. 

On this scale, one is equivalent to doing nothing or standing still and 10 is equivalent to maximum effort. If you rate something a 10 on the modified RPE scale, you feel like you absolutely cannot push your body any harder or you might pass out, throw up, or both. 

For the visual learners out there, here’s a chart depicting the modified RPE scale.

Using RPE to guide your workouts

The RPE scale — whichever one you choose to use — can make your daily routine a lot less stressful and overwhelming.

Example time:

Let’s say the day calls for 5x5 squats at 75 percent of your one-rep max. During your warmup, you notice you feel unusually stiff and your muscles are starting to burn already. 

As you add weight to the bar, you start to dread the 5x5. You do a set of five squats at 50 percent of your one-rep max and you’re totally winded; your legs are already blown up. 

Heed the RPE scale and chill the f*ck out. If the day’s programming is going to send you to an RPE of nine or 10, and tomorrow calls for three mile run, you can use the RPE scale to tone today down a notch. 

If you want to sail through tomorrow’s run, you best stick to an RPE of six or seven today. Even if that means deccreasing the weight for your 5x5 to 60 percent of your one-rep max. 

For those who are more advanced, RPE can guide a macrocycle and enable athletes to perform an entire periodized training plan without faltering. Utilizing RPE, advanced exercisers or athletes can implement a prophylactic rest schedule to keep their bodies from burning out — lest they suffer from overtraining syndrome.  

Drawbacks to using RPE ​

For RPE to work, you have to be honest. Photo by Anastase Maragos on Unsplash.

RPE is an easy and effective way to measure the intensity of the workouts. However, it’s not without flaws. RPE is a completely subjective form of measurement, which yields completely subjective results. This isn’t inherently a bad thing, because subjectivity is the foundation for individualized fitness training, but it can be a bad thing if you don’t use the scale honestly. 

For RPE to help you in any way, you must rate your workouts honestly. It doesn’t do you any good to give a workout an RPE of five when it actually felt like an eight. On the flip side, rating a workout hard when it felt easy or moderate won’t do you wany good in the long run.

Smarter Sweat takeaways ​

Use RPE to guide the intensity of your workouts. Photo by Alex McCarthy on Unsplash.

RPE is an extremely valuable tool you can use to improve your fitness. It’s simple and free, and using it consistently can help you understand how your body responds to different workouts and stressors that affect workouts (such as hours of sleep, hydration, and nutrition). 

For instance, if you do the same workout two Mondays in a row, but you feel more challenged the second Monday, you can use the RPE scale to determine why that is. Lack of sleep, last night’s extra glass of wine, or stress at work could be the culprit behind an RPE of eight, when last week you rated the same workout RPE five. 

Of course, any subjective rating system has flaws. Objective data from smartwatches and activity trackers may not always be accurate either, but together, RPE and tracker data provide a useful framework for modifying the intensity of daily workouts.

Did you like this story? Read more like it: 

• Short on Time? Skip the Gym, Try Trigger Workouts
• 3 Popular Fitness Supplements That Don’t Work (and 3 That Do)
• 6 Reasons You Aren’t Getting Results From Your Workouts
• Workout Afterburn: Is It Real? 
• How to Make Your Workouts Harder Without Going up in Weight
• The Real Difference Between Slow-Twitch vs. Fast-Twitch Muscles
• Is Meal Timing Necessary? ​

By Amanda Capritto

Amanda is the co-founder of Smarter Sweat. She’s a certified personal trainer, health coach, and functional fitness coach. She also helps fitness and wellness brands create robust content strategies and marketing content to explain the science behind their products and services

References

1. Eston R. Use of Ratings of Perceived Exertion in Sports. Int J Sports Physiol Perform. 2012;7(2):175-182. doi:10.1123/ijspp.7.2.175
2. Centers for Disease Control and Prevention: Perceived Exertion (Borg Rating of Perceived Exertion Scale) | Physical Activity 
3. Centers for Disease Control and Prevention. Measuring Physical Activity Intensity Updated September 17, 2020.
4. Centers for Disease Control and Prevention. Target Heart Rate and Estimated Maximum Heart Rate. Last reviewed December 3, 2019. Washington, DC: Centers for Disease Control and Prevention US Department of Health and Human Services 2020 https://www.cdc.gov/physicalactivity/basics/measuring/heartrate.htm
5. Williams N. The Borg Rating of Perceived Exertion (RPE) scale. Occup Med. 2017;67(5):404-405. doi:10.1093/occmed/kqx063
6. Morishita S, Tsubaki A, Takabayashi T, Fu JB. Relationship between the rating of perceived exertion scale and the load intensity of resistance training. Strength Cond J. 2018;40(2):94-109. doi:10.1519/SSC.0000000000000373
   ​7. Muyor JM. Exercise Intensity and Validity of the Ratings of Perceived Exertion (Borg and OMNI Scales) in an Indoor Cycling Session. J Hum Kinet. 2013;39:93-101. Published 2013 Dec 31. doi:10.2478/hukin-2013-0072