Dave's talked about his lats being one of his favorite places to inject, which is what that looks like.
Personally, it hurts like fuck and stays sore for a week. Hurts to raise your arms after. Soreness, I should say. I suppose if you did it regularly (I believe I've done it twice, & when I inject I always do both sides.. except for just 1ml/wk hrt or whatever). You could get used to it with stretching after.