one-platoon system

The one-platoon system, also known as iron man football, is a platoon system in American football where players play on both offense and defense. It was the result of smaller roster sizes in the early days of the game and rules that limited player substitutions, rules that are also standard procedure in many other sports but were eliminated in the 1940s as free substitution was legalized. The alternative system is known as the "two-platoon system", or simply the "platoon system", because of its use of separate offensive and defensive units (three platoons if special teams is also counted).