Whitetx, shapeshifting is very advanced magick. It takes a lot of devotion and time and patience to master the magick.
Shapeshifting often refers to becoming an animal. For example take a witch or wiccan becoming a cat or dog. They are shapeshifting into the physical body of that animal. I don't know if anyone can do this but mental and emotional shapeshifting is possible.
Making your muscles become bigger is called excersize and condition. Diet and stick to a plan. No magick can make this possible. Making yourself taller, I have no clue or anything else becoming larger.