The burgeoning science of happiness maintains there are four basic pillars to being happy: relationships, health, purpose and money. Through the lens of this new science, follow all-time great NFL players as they search for happiness once their careers are over.

The story of college football player Eric LeGrand of Avenel, NJ and mountain biker Steve Shope of Newfields, NH, who both competed at a high level, but suddenly became paralysed on the field.

How the National Football League, America's most popular sports organisation, is confronting the enormous challenge of making the game safer, chronicling the physical toll of the game on its players.

A deeply personal look at another side of professional sports, this instalment focuses on the challenges of balancing the pursuit of professional success and family obligations.