What is the most important thing I can do at the gym to ensure that I will continually build lean muscle?
It's very simple. The most important thing you can do each and every single time you go to the gym if you want to build muscle is to try to set a PR (personal record) on every lift you do. That's it. What this means is that you should always be trying do either do more reps with the same weight (within reason, any sets above 12 on most upper body exercises and 15-20 reps on lower body exercises will do nothing to stimulate muscle growth) or more weight for the same number of reps. Doing the same thing that you have done in a previous workout will do absolutely nothing to help you build lean muscle. The first time you apply a new stress to the body it will adapt by building itself up bigger and stronger. But when it faces that exact same stress again the next time, it will be prepared for it and thus will not adapt again. This is why you have to go up in either weight or reps and try to set a new PR.
Powerlifters and weightlifters continually try to set PR's in contests. They also do this in training by testing their one rep maxes every few weeks or months. But setting PR's does not have to be relegated to singles. You should try to set six rep PR's, ten rep PR's and twenty rep PR's. If you are really serious about your desire to build lean muscle, you always have to be improving. To do this you have to keep detailed records of everything you do in a training journal and always look back at it so you have a goal to shoot for at every workout and on every set you do.
If you really want to build lean muscle, no set should ever be done without the goal of setting a PR. The only exceptions are prehab exercises and times when you are rehabbing from an injury. If you continually try to set PR's on everything you do it gives your workout a much greater purpose and meaning. Not only that but it is a thousand times more fun than just mindlessly going through the motions trying to get a pump. Suddenly your workout becomes something that has quantifiable results that can be measured each and every single time you set foot in the gym. What could be more motivating than that? Chasing PR's also eliminates all the useless junk volume that most people end up doing after they have finished their main exercises.
Even if you start your workout with big exercises like chin ups and military presses and set new eight rep PR's on those, it doesn't mean that when you get to the little exercises and the end like hammer curls and pushdowns that should forget the principle and just do whatever it takes to get a pump. On the contrary, you should still be trying to set a new eight, ten or twelve rep PR on both of those exercises as well.
Forget about adding more sets, decreasing your rest periods and supersetting for a while because none of those approaches will ever help you build lean muscle at a mind blowing rate. If you want to really ramp up the speed at which you build lean muscle and strength, start trying to set PR's on every lift you do and get ready to be blown away by the results you achieve and how much more enjoyable your training will become.
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