The 300 (as in the film about the 300 Spartans) circuit is one of if not the hardest circuit I have ever done, it was one they using when training for the film. It goes like this: 25 full pull ups with an overhand wide ish grip (i.e knuckles facing you rather than chin ups), all in one go if possible, otherwise with the minimum rest between sets, that goes for the the exercises. Straight into 50 dead-lifts with a bar (20kg) + 15 kg on each end. Again no rest, straight to 50 good low press-ups, no rest, then 50 bench jumps, high ones at least 60cm high. Then window wipers, lay on your back, hold the bar (same weight as dead-lifts) in an extended bench press position, then keeping it still, lift your legs (straight legs) using your abbs up and to the left aiming to touch the bar and then the right, the same, and that is 1 repetition, 50 must be completed. Then 50 kettle-bell clean and jerkes with 2 half squats per exercise, 25 on each side. Finally finish with the near impossible second lot of 25 pull ups. The whole thing is a nightmare, but one hell of a good session. Feeling brave? have a go! good luck! let me know how it goes, feel free to call for further details on 07980545324. Michael.