I never heard of growth stunt by doing excercises, but its a possibility. I read somewhere *about.com* that lifting weights dont affect your growth (even young ones), but anyhow just to be catious i would do deadlifts for your lower back, shrugs for your traps and and lat pulldowns for your upper back. Dont push yourself on these excercises like you would with other parts of muscles. Do 2 or 3 sets of 6-10 reps with weights you can do the first set without sweat.
By the way, i too am concerned about my growth i am around 5'9, just turned 16. People say i tall but i dont think so. When do you actually stop growing and how tall am i really doing to be.
Moms 5'2 and dads around 5'11. my bros 5'10 .
so i was just wondering how much growth will it stunt and should i wait to start on the back excercises?