LOL, Marcos...I asked the guy who did mine about weight change and the like, though I'm not sure if it applies to muscle, but he said if the change either way is not drastic, you shouldn't have any problems. I have lost 25 or 30 pounds and my tat has been just fine. It's on my right arm, just below the shoulder. Biceps might be different, but again, as long as the change is not drastic, I'm betting it will be fine. What kind of tat are you getting? I want to get one with of the swirl that's in your avatar