Association football was included in every three editions of International Workers' Summer Olympiads in 1925, 1931 and 1937 as a men's competition sport. Tournaments were played as a single-elimination tournament. Countries were represented by selected teams of their workers' sports associations and the players were mostly amateurs. Exception was the Soviet team in 1937 as it was based mostly on the team of masters of Spartak sports society out of Moscow and participating in the recently established in the Soviet Union competitions of football teams of sports societies, Class A, a predecessor of the Soviet Top League.