somehwere he wrote that you have the 3 exercises you rotate through for each body part, but once any one of those excercises stalls (no longer going up in weight or reps each time you work it out) that you switch that exercise out for a new one and start the process over.
ie: you can't just keep gaining on bicep curls to the point where you curl 900lbs. eventually gains will stop, then change to a new movement and become as strong as possible on that one.