So I've been working out for about a year now, and I'm stronger than some of my friends who have more overall body mass and lower body fat percentage which means they have more muscle mass. Because of this I've been confused as to the science to working out and building muscle and increasing performance in any event, such as more muscle is not neccesarily strength. However, how much of a role does intensity play? I know that recovery is needed in working out, especially with the anaerobic exercises like sprints and heavy weights, but is it accurate to say that working out more intensely more often will lead to overall performance gains more so than following a heavy day/light day routine where you never have consecutive days of heavy lifting/ or heavy exercise or anything that requires 90% and above effort levels. I guess what im asking is what science can say so far about exercise and working out in general for anything that is weight bearing or of high intensity--im not talking about long distance running or biking or anything. I'm talking about short distance track, 50-200m swims, and weight lifting.
And how do performance enhancing drugs play into this such as steroids and HGH?