At Oak Hill Raceway, a motocross track in Decatur, Texas, a night of rain has turned the red soil into inches of soupy mud. As the ground dries in the June sunlight, veteran Chris Livesay gears up for his first ride of the day. Most dirt bike riders will don kneepads, boots, a helmet, and washable clothes. Livesay has an extra piece of equipment: a specially designed prosthetic leg.

We are at Oak Hill so Livesay can put his new leg, which allows its wearers to participate in extreme sports like motocross, through its paces. That is, if the mud dries before another rainstorm rolls in.

This will be Livesay's first time riding on a professional motocross track. But his love of the sport started much earlier.