[gvnonor]

Being in the zone is more acute and recognizable when one plays an outdoor sport for a moderate period of time. I used to play tennis competitively and I could clearly tell when I was in the zone. It would be amazing, I would feel like I could take on anything my opponent would throw at me and without even breaking a sweat. I would expend very little effort but still end up playing the best tennis of my life.

In programming, I doubt if it's as easily discernible. I've been programming for a few years and had a few productive stretches coding 8-10 hours at a time(with small breaks in between of course), but never felt like I was in the zone even once.

[ElliotH]

Easily discernible for me. Its an awful lot like your tennis analogy though.

"I could take on anything my opponent would throw at me and without even breaking a sweat"

If I'm 'in the zone' as it were, you could replace 'opponent' with 'bugs' and it would be very similar to my experience. Not so sure about 'expending very little effort' though. While it doesn't feel like hard work while I'm coding 'in the zone' I end up completely mentally exhausted by the end.

[lloeki]

I started running recently and noticed the zone dawning upon me already. I run around the same path every time (a 3km trail) and try to enhance my performance while evening my pace, so I'm pushing myself. Yet there's a long straightaway where I often start to feel it come in as some sort of positive dizziness creeps in my body and mind (I feel 'lined up' with myself like every part of me is focused together), and the next thing I know I'm 1km later, with a much faster pace than I could expect and a feeling of smoothness and easiness.

I can assure you that it is just as discernible in programming, but I suppose different people experience it with different intensity on the same activities.