Mine rotates. I used to love biceps but now hate them. Chest was my favourite when I first started out and was for years, then I fucked my Tri and chest lagged behind so became one of my least favourites as I felt that it was fruitless training it as I could never push the muscle to hurt due to my arm. However the arm is slowly getting better and chest is once again the daddy! I tried for a PB last night, I failed but will have it next week, it was a superb session and I hurt like hell riding my bike home so I know today I would be in serious pain. I wasn't wrong. I wish all training sessions could be that good.