This piece originally appeared as The Public's Health. 

As the 2018 World Cup moves toward its finale, it's clear that soccer is the global sport, with an estimated 500 million people playing regularly, or about 5% of the world’s population. The game is simple: eleven players on one side try to get the ball into the net on the other side. Of the eleven players, only the goalie can use her hands to keep the ball from getting into the net.