http://www.criticalbench.com/gains/mmp-vault

Obviously there are lots of effective training techniques that
build muscle. The problem though, is that most of them work
slowly over time. With most modern muscle building programs,
on average you can expect to gain up to about 15 pounds of
muscle over a six-month period.

But back in the 60s and 70s, during the 'Golden Age' of
bodybuilding, some lifters were able to pack on up to 25 pounds
of lean muscle mass in as little as four weeks! One of these was
a bodybuilder named Richard Simons, a former writer for Iron
Man magazine.

 

Richard said that he was able to achieve such remarkable
growth by embarking on a grueling program comprised of
9 brutally intense workouts combined with an aggressive
mega-calorie diet. At the conclusion of the program he had
gained 25 Pounds over a period of just 21 days.