Confusion of Cause and Effect

The Swimmer’s Body illusion says that people start swimming because competitive swimmers look amazing and they want the same physique. In reality, competitive swimmers got good enough to compete in swimming because they naturally had that physique, they didn’t get it from swimming. This video explains that, and adds a personal anecdote:

People think I’m big and broad because I played rugby. No, I played rugby because I was big and broad. When my whole school year went to play rugby only the big guys and the fast guys and the athletic guys actually enjoy it, then they continue doing it and getting better. Those that don’t, don’t.