Fitness test = carpet burns?

Having managed the Race For Life on Sunday without any subsequent achilles pain I'm feeling more optimistic, and last night managed a comfortable 4 miler around the Downs leaving a only a very slight twinge. I may have to leave it at that this week as I have a fitness test over the weekend which involves a run and a beep test. The fitness test also involves 50 sit ups in 60 secs and 20 press ups in 60 secs (oh and full press ups not girly crossed legs ones). I was concerned about these but since my running has had to take a back seat whilst old achilles fixed itself, I am easily on track with the core strength stuff and as the achilles are improving I reckon I'll do ok. Of course there is one little problem....

Two nights ago I did my sit ups in loose linen trousers, L was sat on my feet timing me. When I finished I noticed a stinging/burning pain on my but tocks (forrest gump stlye). My trousers had rubbed my skin and I now have something resembling carpet burns at the top and in the crack (ahem) of my bum......looks like I've had a jolly good old time!....not quite.