Remove the soiled shoelaces from the athletic shoes.
Dissolve 1 cup oxygen bleach powder in 1 gallon warm water.
Scrub the surface of the athletic shoes with a sponge dipped in the oxygen bleach solution. Do not saturate the shoes. Allow the solution to sit for 15 minutes.
Dip a toothbrush in the remaining solution and scrub the shoes, concentrating on the stained areas and hard-to-reach spots.
Wipe the shoes with a damp sponge to remove the oxygen bleach residue.
Allow the shoes to dry overnight. Replace the shoelaces with a new pair.