Sometimes I would actually use my heartbeats to help with shooting. It tended to do a sideways figure 8 pattern, so it was "just" a matter of learning when the sights would lead towards a good place and sometimes even pulling the trigger as it's moving towards the target's center. With my awful trigger control, it took a long time to learn to do it well.

Yes!! I also have a sideways figure 8 sight "drift". It's just a matter of timing the trigger pull at the right point of the movement. Granted, it would be great if I didn't have the movement at all... but...

Tell me about it. Then there's the incredible feeling of frustration when you're close to the perfect shot... and then your muscles start to run out of oxygen and build up lactic acid..... 7 seconds in.

I've never had to walk off the line because of it (too stubborn), but everyone else on the team did, every other competition.