The explanation of why some nattys are bigger and more muscular than others is a natural high test level, Im one of em. Never needed steroids....not interested, my friends do them, i dont like the roller coaster of gains and losses they go thru.
Also some guys have mostly fast twitch fibers and grow easiar.....as with test your estrogen can also be out of whack at times...slight gyno usually goes away, as your body cycles naturally thru the year.
