Deadspin and Loser with Socks asks if this kind of muscular enhancement can be found with a good diet, weight training, and maturity. Sure, an athlete can gain a great deal of muscle in one year. Maybe 12 pounds lean body mass by good diet and natural training methods. That would equal about 25 pounds body weight.
If one adds in some nandrolone, HGH, insulin, T, thyroid, the growth can be phenomenal. As seen here. It would be almost impossible to gain raw, complete lean body mass to this degree by natural training.
Does the NCAA test for PEDs? Do the cops find all speeders?