3 years ago I started to stretch my chest/arms. I thought it would help with recovery from weight lifting (bench press etc.). Over the course of a 2 years I went from 185 lbs to 210 lbs, but I noticed a problem! I have big ugly strecth mark scars on the front/back of my armpits and down my biceps. They are still visable after years. I don't beleive my arms increased in size that rapidly to cause it, so I wonder if the stretching could have damaged my skin?
The exercises I did were:
Stick behind neck/back with arms straight (chest/bicep stretch)
Grasp hands together behind back (tricep stretch)
Now I only stretch my legs because I have a fear of making my arms worse.