I'm an industrial electrician. I'm also skinny; people often undrestimate me. Once I had two non-electrician coworkers helping me pull some large wire and make up splices in a trough. One beefy guy was struggling with the wire, so I grabbed it, twisted it around into place. The other guy says, surprised, "You're stronger than you look." I just said, "Sure".

Because of the way the strands are laid, wire has a direction and way it "wants" to go. I'd been an electrician twenty years by that point and knew how to work it. Not strength. Not that I said any of that.

I think it might be like "mechanics feel" they talked about directly in the book zen and the art of motorcycle maintenance.

You get enough experience and you can turn a bolt or screw and tighten it to stretch a little.

Not too little (doesn't hold parts together and/or can come loose).

Not too much (uneven tightening or snap/strip something).

Just right (torque wrenches make this precise).

I think some call that “old man strength”.

Might not be as strong or fast as he used to be, but knows how to do it smartly.

Sometimes the problem truly requires strength and brute force, but not usually.

Even something like taking up concrete. It seems straight forward but you can waste a lot of energy hitting the wrong places.

> Might not be as strong or fast [..] knows how to do it smartly.

Friend of mine worked in Prisons for a while, and has a way of telling the difference between people with a lot of muscle and people who know how leverage their musculature to high effect.

Also using all your motor units to their full capacity (the "invisible" strength) helps. Which usually requires at least some training.

Has this conversation with a friend the other day when an electrical crew came to our place. We couldn't wrap our heads around the way they were able to finish so quickly and efficiently, when for us it would have probably taken days. It's definitely not an easy skill