The American athlete suffered a horrific crash at the postponed Tokyo 2020 Olympics last year.

The crash resulted in Fields suffering from brain shearing and bleeding, a collapsed lung and a broken rib.  

"I wanted to go out on my own terms, and in a way, I still am, despite the thing that I love most nearly ending my life," Fields said on social media.

"I am still here, still riding and still that same kid who loved BMX, just now for the first time in as long as I can remember, starting today, when I ride BMX, it will be for the same reason that I started back in 1999. It will be for fun.

"As I got older, and I watched my competitors retire and move on, it started to sink in that professional BMX racing was not going to be forever."

Fields was released after spending five days in a hospital after the crash in the Japanese capital.

He also suffered from shoulder ligament tears and a partially torn bicep tendon and underwent shoulder reconstruction surgery.

Apart from the Olympics, the Texas-born athlete won the men's BMX title at the Guadalajara 2011 Pan American games.

The 29-year-old also has two golds and a bronze medal in the men's time trial event at the International Cycling Union BMX World Championships.