For years I asked the same question and always seemed to receive different answers. What I did find out through experience was most of the answer but not to the specifics I really wanted.
I finally got smart and realized that I needed to look at the science. Looking at the science is an exercise that is complicated in its own right. You have to look at the definitions of what researchers use in their writings. To some researchers eating 30% carbs in your diet is considered low-carb (In what universe??). Every time the science seemed to contradict a ton of other studies there was always a dispute in definitions that were poorly used to create a bit of drama in the news.
1-6 reps = Strength – This rep range focuses most of the muscular change on the neurological system of the muscle. Over time this rep range will cause an increased amount of muscle fibers being recruited for heavy lifting. The longer you lift in this range the more of the muscle is used to life. This is a very valuable developmental step that beginners should start with.
7-12 reps = Maximize muscle growth – This increases the size of the muscle but may necessarily increase strength. The change to the muscle is mostly cellular and metabolic. Increases in strength are minimal compared to the lower rep ranges.
13+ reps = Endurance – This range increases the mitochondrial health of your cells and can increase the number of capillaries in the muscle. This gives you increased endurance in the muscle with very little hypertrophy or strength gain. This does increase the number of mitochondria in the cell which will increase the size of the cell but will not lead to large hypertrophy gains.
The best workout plans for overall health includes working out in all three ranges but for the point of our experiment we will be focusing on HYPERTROPHY!
Which means my workouts will mostly consist of 3 sets of 10 reps at 75% of my 1 Rep Max