Adam felt his cock quiver, so long and so thick it was now between his pecks in the deep cleft over his breastbone. He tried to reach for it but his arms were too musclebound to do more that stick out at his sides, and still his muscles continued to swell and his cock to grow until it started to poke him on the underside of the chin.
He stiffened in pleasure, his pecks tightening and then squeezing the shaft of the mammoth cock. Oh god, Adam realized, he could give himself a titty-fuck! And with his own pecs!
Flexing his pecs and rubbing his chin against the member was all that he could do at first, but his excitement grew as he began to orgasm, every muscle tightening and then...they began to get even tighter, cramping up and straining, feeling as if they were going to tear apart as the growth that had affected his muscles and soft tissues soaked into his bone marrow and the bones began to grow as well.
Adam felt himself stretching on the rack of his own muscles. Taller and taller, wider and wider, his clothing shredding away, until the bone growth overtook the muscle and cock growth and surpassed it. He was becoming a giant, and a skinny one at that.
When he was finished, he was hunched over in the room, bony and gaunt, the huge musculature now stretched into long ropy sinews that barely covered his lanky frame. His cock no longer poking him in the chin, now instead just erect slightly past his navel. He was a giant.