Porridge.

I was in training for a particularly bizarre job in the military, and it came to the fitness test. Now, the test itself isn't that strenuous - you run a certain distance in a certain time. I was able to do the distance with ease on the roads, but the test, it was decided, was done on the treadmill at a gym.

So I load up in the morning on a whole load of porridge (for the energy), and get on the treadmill. This throws me almost immediately because I'm not used to it, and because I'm a huge guy - my stride basically means I can cover greater distances. Anyway, the machine starts, and you're allowed to slow for a breather once.

The trainer running the test keeps chanting "Do you want to slow down, tell me you want to slow down" at you. And I don't know if that's part of the test, like psychological hazing, or if she was just being an ass, because I took the breather when I didn't really need it. Anyway, about two minutes later, I've got three minutes left on the test - and the porridge hits.

I feel my chest going crazy. It feels like a solid lump of hurt. And I realise that the porridge has given me gas. Gas pains strike, but I'm running at such a rate that I can't really do much but keep going. And this trainer is still shouting at me that I can slow down if I want to.

So I get trapped gas confusion, and go 'OK', and the machine slows down, and I let rip with all my porridge-related trapped wind. At once I'm fine again, and say 'OK, speed up'. But no... no. The test is over. And I have failed.

I was allowed to run the test again, but after the porridge incident I didn't really want to go through the hassle. At the same time I was offered an alternative job, so decided to take that.

TL;DR: Failed a fitness test because I had trapped wind, couldn't be bothered to resit it.