I am curious if this happens to myself only, or if it happens to others. Yesterday was leg day for me, with emphasis on the quads. When I woke up this morning, I would tense my quads and they get as hard as a rock. With any other muscle group, this never happens. For my chest or arms, they feel mushy the next morning upon rising. My diet and post workout nutrition has been the same for all body parts, with the exception of more calories added to my post workout shake for legs (extra carbs and protein). Does this happen to anyone else, or can someone at least explain what is happening here? Not so much that it matters but I’m very curious.
This also happens with my penis but I just have my girlfriend massage it until the stiffness goes away. 
I have the same problem as “D” usually occurring when I wake in the morning. Problem is, I don’t have a girl friend so I must use a more personal solution. Mind you. its still fun. Graham
Actually I just went thru the exact same thing. I did legs yesterday and today they are so pumped and hard I can hardly stretch them. I think it may be some esterfied gear kicking in after 3 weeks.