I place the crank horizontally on a block of wood, orient the wrench so that I can press the wrench handle down with my foot, give it a test press to make sure everything is secure and the wrench won't slip, then stand all my weight on the end of the wrench handle. Gradually the first time, if that doesn't work then suddenly. That is some 200 ft lb of torque and no pedal has ever failed to budge. If you sort of hop up then come down, you can probably generate 300 ft lb momentarily.