"Muscles" - he big bulgy kind - are actually relative newcomers to the track racing world. Prior to the 1980s or so, even the sprinters were working on "supple" rather than "big". It was the East Germans (Lutz Hesslich in particular) who introduced the bodybuilder physique to track racing in the early-to-mid 1980s, and steroids are known to have played a part.

BTW, here's Fred Rompelberg in his prime.


Despite his "climber's build" he was a top motorpace racer and is the current world speed record holder at 167 MPH. He turned a gear of 390 inches, which is roughly the equivalent of a 164x11. (He used a double reduction system.)