Logic

People often search their memory to identify an incident which injured their back, despite feeling nothing at the time.

“I didn’t really feel that I’d done anything at the time to bring it on. Cause it didn’t happen instantaneously after my run, it happened like the next day”

37 YEAR OLD MALE WITH ACUTE PAIN

Unless someone is in a life or death situation, it is unlikely their brain will ignore a significant back injury.
It is also illogical that someone could significantly injure themselves while doing something which they regularly do without problem.

“it wasn’t like I was causing any strain, and it’s a motion that I do all the time, and yet, somehow it just suddenly like caused this pain to happen”

36 YEAR OLD FEMALE WITH ACUTE PAIN

This does not mean that their pain did not start while doing that activity, but they do not need to worry about serious injury. Nor do they need to avoid that activity in future.