I told Denver to stop doing burpees. Here's what twelve years changed.

The burpee was invented in the 1930s by Royal H. Burpee as a test — a short assessment of agility and coordination, scored over about twenty seconds. Eight was a poor result. Thirteen was excellent. One set, and you were done.

It was never designed as a daily staple, and that distinction still matters. Somewhere between the 1930s and the modern group class, a twenty-second assessment turned into a hundred repetitions on a Tuesday. A test and a training tool are different objects. Using one as the other is how a reasonable movement becomes an unreasonable dose.

I also still think it's a poor default for most people who walk into a gym. Not because it's dangerous — I'll come back to that — but because it demands hip and ankle range that a lot of desk-bound bodies simply don't have available yet, and it demands it fast, repeatedly, while tired. There are better first choices.

I told a general audience that a common exercise would wreck the two body parts they were most afraid of damaging. I used words like imminent injury. I said they'd miss their knees when they were gone.

In the years since, I trained in Cognitive Functional Therapy, and the central thing it taught me is that what people believe about movement changes how their body responds to it. Someone who believes bending is dangerous braces before they bend. The bracing itself becomes the problem. Fear of a movement reliably makes that movement worse, and the fear usually arrived from somewhere — a scan, a clinician's throwaway line, an article by a confident trainer.

I now spend most of my week unpicking exactly that in people who've been told their spine is crumbling or their knees are bone-on-bone. And in 2013 I was writing the sort of thing that puts it there. That's an uncomfortable thing to notice about your own back catalogue, and it's the honest reason this page exists.

Pain that persists for months, wakes you at night, radiates down a limb, or comes with numbness or weakness is a different conversation and should be assessed properly — not trained around and not simply avoided.

But the more common story in my studio isn't a damaged knee. It's someone who has quietly stopped doing fifteen things, each for a sensible-sounding reason, and now moves through a life that has narrowed around them. That's the pattern Cognitive Functional Therapy is built for, and it's why I'd write that 2013 column very differently today.