Muscle Man

Golden Age Origin
Muscles is a gang heavy, enhanced with the mob boss’s serum into a man of steel and iron. The gang conduct a train robbery, with Muscles using a giant rock to block the tracks. Abord the Century Limited, Keith Spencer transforms into Captain Flash and stops it from running into the back of the blocked train. Chasing the fleeing gang, Captain Flash is knocked out by Muscles.

Determined to lure him out, Captain Flash openly challenges Muscle to a fight - the winner taking one million dollars. Flash is able to bare Muscles' blows and manages to take him in the third round.

Powers and Abilities
Not very intelligent, Muscle Man is superstrong and possessing a degree of invulnerability - as he's seen to be bulletproof yet Captain Flash is still able to knock him out.

Golden Age Appearances
Captain Flash #3