50 times is a bit too much for me, and probably a lot of other people. It leads to mental or cardiovascular fatigue, which is not what I'm after when building m

50 times is a bit too much for me, and probably a lot of other people. It leads to mental or cardiovascular fatigue, which is not what I'm after when building muscle/strength. If you're an endurance athlete it would be more appropriate. When training for muscle size the important thing is to fatigue the muscle itself, which is easier to do with 5-20 reps, maybe 30 at the most if exercising small muscles. Regarding "low reps", that usually refers to sets of 1-3 reps very close to your maximum potential. Once you go above 5 reps or so, the risk of injury is much lower. There are lots of beginner programs using sets of 5 reps, and people aren't getting injured left and right on those.