its better than not doing any reps at al;l, but for the reasons your saying do them as strict as possible then cheat on the last reps. i love cheating o ncurls when im swam0ped from doing them strict...
ARching to get those last reps in is better than not doing them at all. kind of like curling 40 pounds for 10 then doing 5 cheat curls to overload the muscle as opposed to not doing the 5 more.
still youre 13 youre supposed to grow a lot more., if you stop at 5'4 im pretty sure its b/c of squatting., were you 5'2 at 12? when did you start squatting? i started lifting at 15 i was 5'7.5 lols.
LOL i wouldnt let you squat either if i was them youre 13 and 5'3. it might **** you up lol. btw strong deadlifts. youre gonna be ten times stronger than me lol.