Kevin Plank was relatively small for an American footballer, and when he weighed the cotton T-shirt he wore under his team uniform, he found it weighed three pounds because it was so drenched in sweat. Knowing he couldn’t hinder himself in this way, he set about finding a material that wasn’t so absorbent. Going to a local fabric shop, he soon learned that synthetic materials would not take in as much sweat, so he had a shirt made and found it added just four ounces over the course of a game. When he gave some team-mates samples to try, they also soon saw the advantages. He began to produce the shirts commercially, and now Under Armour is a $2 billion global brand used by people from every sport.