How much pain is OK when you train?

Written by Coach Moose. Not yet reviewed by a physiotherapist. · Published 6 November 2026

You've probably heard "no pain, no gain," and you've probably heard "if it hurts, stop." Neither one helps when your knee is a bit grumpy and class starts in an hour.

The honest answer: nobody has proven a magic number. There is still a useful way to think about it.

The short version

Sharp pain, swelling or anything on our warning list means stop and get it checked.
Some discomfort during exercise can be acceptable for some long-running problems, but pain isn't required for progress.
The number on a pain scale matters less than what happens next.
Check how it feels the next morning.

What the research says

A 2017 review pooled 7 trials and 385 people with long-running pain in the back, shoulder, Achilles or heel. People doing painful exercise had a small short-term benefit over those doing pain-free exercise, and there was no long-term difference in pain or function.¹ None of those trials looked at knees. The painful exercise groups also used heavier loads, so the load itself may explain some of it.

In a trial of 38 people with Achilles pain, those who kept active with pain monitoring did no worse at 12 months than those who took six weeks of active rest.²

So the fair summary is that pain during exercise isn't automatically harmful, and it isn't necessary either.

Where the 5 out of 10 idea comes from

You may have seen a rule that keeps pain at 5 out of 10 or lower during activity, returning to baseline by the next morning.³ It's used in practice, including for tendon pain. One tendon trial used stricter limits of 3 out of 10 in its loading group.⁴ We didn't find validation of any single number, so use these as guides.

Our coaching traffic light

This is how we coach it at CrossFit BC. It's a rule of thumb, not a clinical test.

Signal	What it feels like	What to do
Green	Mild discomfort that eases as you warm up, and you feel normal the next morning	Keep going
Yellow	It builds during the session, or you're sorer the next morning	Lower the load or range next time
Red	Sharp pain, swelling, giving way, or you change how you move to avoid it	Stop that movement and get it looked at

Coach note

Keep a simple note after training: what you did and how it felt the next morning. A week of notes tells you more than one tough session ever will.

Quick answers

Should I train through pain?

Don't push through sharp pain, swelling or giving way. Mild discomfort that settles quickly may be OK for some long-running problems. If you aren't sure, ask a physio.

Is soreness after a workout the same as joint pain?

Not always. Muscle soreness after a hard session is common. Pain in the joint itself, swelling, or anything that keeps coming back is worth getting checked.

Should I take a painkiller so I can train?

Check with your doctor or pharmacist. Pain relief can hide the signal you're using to judge the session.

Not sure if it's OK to train?

Tell us what's going on. A coach will help you work out your next step, including whether to see someone first.

Talk to a coach

About the author. Dai Manuel, known around the gym as Coach Moose, has 30 years of coaching experience across strength, conditioning and lifestyle coaching, and is a co-owner of CrossFit BC in Vancouver.

This article is general education, not a diagnosis or treatment plan. If you're unsure what's going on, or it isn't improving, see a physiotherapist or physician.