Here's something that confuses about weight training: If one wants to make gains in muscle size, one must gradually increase the weight they are lifting, right? Yet at the same time, I hear that one must change their workout routines every 6-12 weeks in order to see good gains or whatever. So how can I significantly progress in the amount of weight I'm lifting in a particular exercise if I'm supposed to switch to a new exercise after a while? This concept of switching routines/bugs me: I want to keep keep track of my progress on a given exercise and increase the weight I'm using -- not have to abandon it after 8 weeks to start a brand new exercise. And then have to abandon THAT exercise after 8 weeks in favor of something else... Why can't I pick a machine/exercise, start at 10lbs or whatever, and see if I can get up to 100 lbs in six months? Why must I stop and switch to something new and start all over again every few weeks?