Growing spells can effect all asepcts of growth. As people grow they become stronger, faster and taller. This is due to the foods we eat and our genetics, but that doesn't mean these things can't be helped along with a little bit of magic.
Because you are dealing with the powers of life when dealing with growth spells it is important to make sure you cast these spells exactly as stated. When a spell is miss-cast the results are always extreme and always against the caster.