do you have a route or style in mind or just after general fitness
Good to see this topic resurrected, as an old-school counter to the scary new ideas going on over on the RPs thread (although doing them tomorrow). FOC is like the Carlsberg special brew of sport-climbing training imo. It simply gets you sickeningly boxed out of your tree really quickly and leaves you fucked for the next two days. It hones you to a sharp point ready to fight like a battalion of amphetamine-fuelled shock troops. Conditioning yourself to fight the pump and cling on for dear life is what climbing at your limit o/s or r/p (or at least attempting to, before falling off, boxed) is all about for the sort of pumpy short to mid-length climbs most people do on most crags. None of that getting it totally dialled and cruising it with barely a flicker into the anaerobic zone. The pseudo-scientists will tell you about the risks of over-development of your lactic production with concurrent underdevelopment of your aerobic and anaerobic capacities to deal with said lactic. Ignore them, they probably have time to train 12-14 week blocks of energy system nonsense, aspire to climb further than 17 metres, and enjoy flavoured craft beers.
Now we're speaking my language! When I did FOC, I started off with minute on, minute off x8. Ten minutes rest, then do it again until failure. As you get fitter drop it down to 1 minute on, 45 seconds rest, then 1 minute on, 30 seconds. Once you can do this easily you need to either speed up or add a bit of weight. Aim for a move a second (a metronome helps for this). It is crushingly boring but gets you fit. Try and minimise time shaking out/chalking up.
Tape your pinky fingers! They get battered & calluses from FOC.
shows how little I’ve managed to climb since having a baby!