What is RPE, and why do coaches trust a number you make up?

You finish a session, open the app and it asks you one question: how hard was that, from 1 to 10? It can feel almost too simple. There is no sensor, no lab and no formula, just your own judgement. So why do coaches and sport scientists take that number seriously?

Where RPE comes from

RPE stands for rating of perceived exertion. The idea goes back to the Swedish researcher Gunnar Borg, who developed scales for people to rate how hard physical work felt. His original scale ran from 6 to 20, roughly mirroring heart rate in young adults divided by ten. Later he introduced a category-ratio scale running from 0 to 10, with verbal anchors such as "easy", "moderate", "hard" and "maximal" attached to the numbers.

That 0 to 10 style of scale is the one most coaches use today, and it is the basis of the 1 to 10 effort rating in Train Climb.

Why a "made up" number works

Perceived effort is not random. When you rate a session, your brain is integrating a lot of information at once:

• how hard your heart and lungs worked
• how pumped or tired your forearms got
• how much concentration the moves demanded
• how fresh or flat you were before you started
• how long it all went on

No single device measures all of that. A heart rate monitor, for instance, says very little about a short, maximal bouldering session where your fingers are the limiting factor and your heart barely gets going. Your own rating captures the whole experience, which is exactly what matters for climbing, where so much of the stress lands on small tissues rather than the cardiovascular system.

Research on session-based effort ratings, notably the work of Foster and colleagues (2001), found that a simple post-session rating tracked heart-rate based measures of load reasonably well across a range of activities. It is not perfect, but it is good enough to be genuinely useful, and it costs nothing.

RPE is not a guess about the session. It is a summary of how the session landed on you.

What makes ratings reliable

The number becomes more trustworthy when you rate consistently. A few habits help:

1. Rate the whole session, not the hardest moment. One brutal attempt on a project does not make a long, mostly easy session a 9.
2. Rate a little after you finish. Foster's method suggests waiting around half an hour, so the last few minutes do not dominate your memory. In practice, rating once you have cooled down and packed your bag works fine.
3. Use the anchors. Think of 1 to 2 as very easy, 3 to 4 as comfortable, 5 to 6 as solid work, 7 to 8 as hard, and 9 to 10 as close to everything you had.
4. Be honest, not heroic. Inflating or deflating ratings hides the very trends your coach is looking for.

Common worries

"My 7 is not the same as my friend's 7." True, and it does not need to be. RPE is most useful for comparing you with yourself over time. Your coach reads your trends, not your number against someone else's.

"I am bad at judging effort." Most people get noticeably more consistent after a few weeks of rating every session. The act of rating itself trains awareness.

"What about young climbers?" Children and teenagers can use effort scales too, though they may need clearer anchors and a bit of coaching on what each number means.

Why it matters

On its own, a rating tells your coach how a session felt. Multiplied by the duration, it becomes a measure of training load, which is where things get really useful. That is covered in Session-RPE: turning effort into training load.

In Train Climb

• Every session you log asks for effort from 1 to 10. Take two seconds to think about the whole session before you tap.
• Use the notes field when a number needs context, for example "felt a 6 but fingers were sore".
• Rate every session, including easy ones. Low ratings matter as much as high ones for seeing the full picture.
• New to logging? Start with Log a session in 30 seconds.