14 years old having problem with reps
My main language isn't English so sorry if I wrote too much.
I'm in the middle of 14-15 (~176 cm) and in recent times I started getting uncontrolled weight (~70 kg) and this extra weight isn't muscle weight but rather fat (I don't want to say a lot about this because my knowledge about nutritional value, etc. is very low) I decided to lose weight and also gain muscle weight. I'm fond of going to med tempo walks for 1,5 hours to 2 hours so losing weight isn't going to be a problem. Now the real problem is, dumbells. I'm currently making curls and db curls but after sometime my arms get locked, not pain it literally locks. Like, it hurts but even if i try to force it I physically can't lift it. Is this something that happens ? Or is it a problem on my side do i rest longer ? This happens in 2 scenerios:
I make 10 reps then decide to switch to 15 and it hurts but when i try to return to 10 again I can't continue doing that either..
Or
I make only 10 reps and it happens after sometime again
I'm starting to think that I rest for a short amount of time, mostly 1-1.5 minutes. But when i rest for longer I'm afraid that it will be too much.