In the world of fitness, we often live by the numbers. Recording every pound lifted, every mile run, and every beat of our heart rate. While these metrics are vital for tracking performance, they don't always capture the full picture of how your body is actually responding on a given day.
That is where RPE, or Rate of Perceived Exertion, is useful. Two Mondays with the same training prescription can feel completely different depending on sleep, stress, and what the rest of your week looked like.
HeartKore is a minimalist approach. Four bodyweight exercises, one interval that starts and ends every so many seconds. So instead of asking how much work you did, we ask how hard it felt. That number is RPE, and it shows up throughout the app whenever you log a training session. This page explains what it means and how to use it properly.
What is RPE?
RPE stands for Rating of Perceived Exertion. RPE is a subjective, internal scale used to measure how hard an exercise feels. Instead of relying solely on external tools, you listen to your body’s signals. Breathing rate, muscle fatigue, heart rate, how close you were to your limit. All of it gets compressed into a single number.
The scale most people use today runs from 1 to 10. It was adapted from the original Borg Scale, built by the Swedish researcher Gunnar Borg in 1982. Borg's version ran from 6 to 20, deliberately set to roughly track heart rate, so a rating of 13 lined up with a heart rate near 130.
Studies since then have kept confirming the same basic point. What a person feels during effort tracks closely with what their heart rate and oxygen uptake are actually doing. That is why it works, even with no equipment involved.
The Original Borg Scale
Borg's original 6 to 20 scale is still used in research and clinical settings, but it is clunky for day to day training. Nobody wants to think in a range that starts at 6 mid-set. It exists mainly so you understand where the modern scale came from, and why the numbers are not arbitrary.
The Modern 1 to 10 Scale
This is the version HeartKore uses. Lower numbers feel light and sustainable. As the number climbs, breathing gets harder, the working muscles fatigue faster, and your ability to keep going drops off.
| RPE | What it feels like |
|---|---|
| 1 to 3 | Light. Breathing controlled. Can hold a full conversation. |
| 4 to 5 | Working, but comfortable. Breathing noticeably elevated. |
| 6 | Effort is clear. Conversation shortens to a few words at a time. |
| 7 | Hard but controlled. Some gas left in the tank at the end of a round. |
| 8 | Very hard. Form starting to cost you something. |
| 9 | Close to the edge. Barely holding form together. |
| 10 | Absolute maximal effort. |
RPE vs Reps in Reserve
Reps in Reserve, or RIR, is the mirror image of RPE. Instead of asking how hard a round felt, it asks how many more reps you could have done. The two map onto each other directly. Two reps left in reserve is roughly RPE 8. One rep left is closer to RPE 9. Nothing left is RPE 10, which is another way of describing training to failure.
Some people find it easier to count reps they did not do than to rate a feeling out of ten, especially early on. Either route gets you to the same place. Use whichever one your brain grabs onto faster mid-round.
Why RPE matters in a HeartKore EMOM
Every round has a fixed rep count. What is not fixed is how hard you push to get there. RPE is your live dial inside that round, going harder or easier while the reps themselves stay the same. Push it and the round costs you more. Ease it and you save something for the rounds still ahead.
Once you finish, log your RPE, either as one number for the whole session or exercise by exercise if you want the advisor working with more detail. That log is what the advisor runs on. It reads your RPE and shapes what gets prescribed next time, aiming to land you somewhere between RPE 6 and 8. Rate too low too often and the next session asks more of you. Rate too high too often and it eases off.
Be honest rather than optimistic. An RPE 9 logged as a 7 does not make the next session easier, it just means the advisor is working from the wrong information. Consistent, honest logging is what keeps your prescribed sessions landing in that 6 to 8 band instead of drifting too easy or too brutal.
RPE does not change how many reps you owe this round. It decides what tomorrow's session looks like.
Over weeks and months, the same prescribed session should feel less brutal to log. That is the actual sign of progress in this format. Not a new movement unlocked, but the same four exercises costing you less than they used to.
FAQs
Is RPE accurate for beginners?
Less so at first. If you have never trained close to your limit, you will not yet know what your own limit feels like. Most beginners either play it too safe or go too hard. Accuracy comes with reps, not instructions. Give it a few sessions before you trust your own number.
What does RPE 7 feel like in an EMOM?
Working hard, breathing hard, but composed. You finish the round with two or three reps still in you if you had to keep going. Your form has not started falling apart yet.
Should every round be RPE 9 or 10?
No. Training at the very top of the scale every round builds fatigue faster than it builds capacity, and it wrecks your pacing for the rounds still ahead. Most of a session should sit around RPE 6 to 8. Save the higher numbers for the rounds designed to ask more of you.
Can RPE replace a heart rate monitor?
They do different jobs. A heart rate monitor gives you a number regardless of context. RPE gives you the context. Used together, one confirms the other. Used alone, RPE is still enough to train properly, with or without the tech.
No measurement, no formula, no tech required. Just an honest answer to one question every session. How hard did that actually feel?
Log your RPE after every session and HeartKore's advisor shapes what comes next, keeping you around RPE 6 to 8.