I am cycling like there's no tomorrow and yet I am going nowhere. I am like Lance Armstrong but with both testicles. However, like a washing machine that's shaking and making loads of noise, I am coming to the end of my cycle. I glance over my shoulder and notice that there is a treadmill free. There are only five treadmills at our Gym and invariably they are being used by Suzi and her friends, taking time out from looking after their vermin offspring, so they can have a read Bella's latest article about some woman who has cheated death a dozen times by eating nothing but leek soup. They also get a chance to show off their new "Tramp Stamp" tattoos.

I rush with urgency and throw my towel down onto the treadmill. Thankfully there are no Germans in our Gym so this is a legitimate way of reserving a treadmill. I bash in my speed and time and start going. I put one foot in front of the other and beginning running.

Oh Crap! (Not literally) The movement has made me realise that I could really do with a crap. I can feel something wiggling around inside my bottom. I have already started running but I could stop and go to the loo. That would mean cooling down and then warming up again and I could lose my treadmill. The other option is to hold this for 5 kilometers. I feel an empathy with Paula Ratcliffe.

Oh Crap! (Not literally) I wonder if it's just wind? I daren't fully release my sphincter - just in case anything else decides to pop out as I can feel it pushing at the doors. I slowly release and allow myself a small push. Some air seeps out silently and the smell of rancid eggs wafts through out the gym. I am quite proud of my effort, so I smile to myself.

Oh Crap! (Not literally) I've only done five minutes and now the other four treadmills are all free. I could've gone for a crap and got back on a treadmill. And I could even have got the treadmill near the TV showing the Simpsons.

Oh Crap! (Not literally) It's been 15 minutes since I last thought about needing the loo. Using a mixture of listening to my iPod and concentrating on the hypnotic jiggling of some of the people near me; I had nearly forgotten about it. Now I've remembered and it's back with a vengeance. I squeeze my internal muscles in a rhythmic pumping motion to see if I can push it back in.

Oh Crap! (Not literally) I've finished my run. I grab my towel and water bottle and head for the toilets. After having run 5 kilometers, traversing the 10 meters to the toilets shouldn't prove too much of a problem. I feel like I am treading water. The toilets are getting further away. I am in pain. It feels like a knitting needle has been shoved through my bottom and into my bladder.

Eventually, I cross the finish line and lock the door.

Oh Crap! Literally.