IIRC, Hank Pym had heart troubles sometimes due his his size-changing, the enlarging especially. He got stuck at 10 feet tall for a while and had to constantly take medication to keep from having a heart attack. So someone who had enhanced musculature without an enhanced heart would have issues as well.
I'm reminded of the novel "Spider-Man: Down These Mean Streets" by Keith R.A. DeCandido. One of Peter's students (from when he was a teacher) took gamma radiation-enhanced ecstacy, Hulked-out, then later died in the hospital from a damaged heart. Peter even referenced Hank Pym's issues with size-changing.