Listen to the Master: Jerry Moffatt
In the winter I train power, for three reasons: Firstly, an increase in power leads to an increase in endurance — it doesn't work the other way around. Secondly, you retain power longer than endurance — after a lay-off you'll still be able to do hard boulder prob¬lems, but you'll be crap on routes. Thirdly, you make smaller power gains, and power is much harder to get [than endurance].
Training power you must be totally commited and give it 100%. That’s what power is all about. If you give it 90% you’re not really training power. With endurance you can give 70% or less and still get a lot out of it. The two are totally different.
Not the other way round
Power training on one or two moves problems will help your endurance but not the other way round.
Never strong enough
Because your fingers are the link to the rock, finger strength is probably the most important strength you can have. Your fingers can never be strong enough.
The biggest mistake
The biggest mistake I've made over the last 15 years is not stretching, and I'm paying for that now in injuries. I don't take my clothes off and sit in front of the fire, but I do stretch my fingers, wrists, elbows, shoulders, neck, and back, a little all the time. I stretch my fingers so habitually that I don't even know I'm doing it.
Too much training is as bad as not enough
[John] Bachar […] taught me the importance of rest days. You can take it for granted that peo¬ple will train; it's when and how much they rest that's variable. Too much training is as bad as not enough. Too many people think, "This is my power day, and I'm going to do it." I try to be flexible and listen to my body.