Historically speaking, sports originate with military training. Some sports are more pure expressions of that origin than others, but few sports could compete with actual grenade throwing for practical applications during combat.
Weird Universe tracked down an online copy of a 1918 athletic training guide aimed at branches of the Knights of Columbus, a Catholic fraternal organization, in the United States. The United States was massively mobilizing and adapting for its first major war since 1865, so it was necessary to get as many young men ready for modern combat as quickly as possible. Sports should therefore reflect battlefield needs, so Captain Lewis Omer of the newly-formed 86th Infantry Division proposes that young men practice grenade throwing as a sport.
The rules and field reflect life and death in the trenches of Europe. The player is inside a cage simulating a trench. In sixty seconds, he must throw as many grenades as possible into boxes at different ranges representing enemy trenches. Between each throw, he must hit the ground, touching his knees and his chest to floor of the cage. Close, as they say, only counts in horseshoes and hand grenades, so land the grenades as close to the target as possible for maximum points.
The rest of the document is also interesting to read. Immediately after the section on grenade throwing is a description of Trench Ball, an adaptation of football for trench warfare.