is it bad for a young person 13 years to use 25kg dumbbells to gain muscle I am now 13 and currently injured with a cast on my leg but i fell very active. I have borrowed some dumbbell weights with 2 x 1.25kg, 2 x 2.5kg discs I was working out yesterday and my biceps are a bit sore so I won’t workout. I will work out 1day then rest on the other. Am I too young to work out? Will it stunt my grown because I am already pretty short 155cm roughly? And is about 2.5kg good on my arms? For my age? (It’s not too heavy or to light for me) can i start working out a bit with 5kg on each arm without stunting my growth or completely tearing my muscle fibres? I am pretty skinny and have added a bit of mass over the 6 weeks while I was in cast but only on my belly. My arms and chest still look pretty skinny and I find it really hard to gain weight and I have a fast metabolism so when I do, I burn it off. When I wasn t in cast I was playing football every day and running and very active. But I was still very skinny and weak but i did have a weak six pack (which is now gone) when my leg fully heals ( 6 weeks) i will go back to playing football all the time and i might start doing push ups and crunches every day (50 -100 reps).but i am scared to lift dumbbell weights in case it might create problems in the future. Yet I don t want to be weak and I like working out while listening to music once every three hours (5 times a day). But is it dangerous at my age? Should i only do very light work outs or can i do what feels good 2.5kg (not to heavy not to light)? Can i occasionally go a bit heavy 5kg? Or should i wait until i am 16? Could you recommend a routine? P.S this is my first question tell me what you think please i would appreciate it ;D or tell me what I can do about my weight? Also will getting good definition on my body (chest, back, core, biceps, triceps etc.) be hard for my age without creating problems in the future.