oh ok, thanks for correcting me.
http://espn.go.com/espn/page2/story/_/id/6933214/tmq-mel-kiper-jr-size-increase-football-players
Kiper's numbers: From 1991 to 2011, top-five offensive tackles increased from an average of 22 reps of 225 pounds to 26. Top-five guards increased from 22 to 29 reps. Top-five centers increased from an average of 21 to an amazing 30 reps. A generation ago, coaches put quick, crafty players at center. Today centers are muscle-bound specimens.
Roll Kiper's numbers together and here is what you get: Today's offensive linemen are on average 24 percent heavier than those of 1979, plus an average 31 percent stronger than those of 1991.