Mate, first thing to grasp is they're not looking for the finished article, just someone with the potential to be one.
I dont know what the requirements are today, Ninga does and will sort you out on them. They have to do a bleep thingy now, if they'd of done that with me I'd of failed, every other word would have been bleeped.
Chin ups, man ones only, no girlie shite. Hands on the outside of the bar facing you....much fun.
Sit ups, these are fairly easy after a while, just knock them out.
Press ups, dont kow the required number but after basic I cracked 60 out for a bet in a oner, things you'll do for a pint.
Like I said they arn't looking for the finished article, just someone with the mental strength and bollocks to complete the course. Most dont, go for it.