RPE and sRPE: how to measure a session’s difficulty yourself, even without a watch
The cheapest sport-tester is in your head. The RPE method is used even in elite sport because it captures how hard a session really was surprisingly accurately — and needs no watch.
What RPE is
RPE (rate of perceived exertion) is your subjective rating of how hard a session was, on a scale of 1 to 10. One is a stroll, ten the absolute maximum after which you can’t catch your breath. You log it ideally 20–30 minutes after training, when you have some distance from the hardest moments.
Turn RPE into load: sRPE
The number alone is fine, but the magic comes when you multiply it by the session length in minutes. That gives you sRPE — load in units (AU, arbitrary units):
Example: a 75-minute session at difficulty 8 = 75 × 8 = 600 AU.
Add up the AU over a week and you have weekly load — exactly the number you need for tracking the trend and for the acute-to-chronic workload ratio (ACWR).
Why it works
Perceived exertion correlates well with the body’s internal load — the body “knows” what something cost it even if you don’t measure it with a device. On top of that, sRPE captures what a watch doesn’t see: a hot day, nerves before a match, poor sleep. That’s why it’s so popular with coaches who don’t have the whole team wired with sensors.
Common mistakes
- Rating right away in a rush of emotion. Wait a few dozen minutes and the number will be more accurate.
- Confusing “I didn’t enjoy it” with “it was hard”. RPE is about physical difficulty, not mood.
- Inconsistency. The value grows with regularity — one entry says nothing, two months do.
How NEXT8 handles it
In the evening log you just tap the difficulty and length and NEXT8 works out the rest — it builds weekly load, the ACWR ratio and the basis for injury prevention from it. If you have a watch, the app can also compute load from heart rate; but RPE works with nothing at all.
In short
- RPE = the sense of a session’s difficulty on a 1–10 scale.
- sRPE = minutes × RPE = load in units (AU).
- It works without a watch and accounts for heat, stress and sleep too.
- Rate with some distance and regularly.
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