why does my elbow crack when i do tricep exercises

    

 

 

ok when ever i do these


or something like that i go up and either my left arm or my right just above my elbow cracks (or sorta pops) and after a while it starts to hurt and gets really annoying, my friends have all said they have had the same problem alot before, does any1 know what it is or how to make it stop?