With the Olympic games approaching, athletes all over the world are training hard and dreaming of gold, silver or bronze.

Many of the athletes have overcome great adversity to get to the pinnacle of their sport.

But few have travelled as far, and gone through greater hardship, than one young man who is training to represent the US in the London games.

Al Jazeera's Rob Reynolds reports from Beaverton, Oregon, on South Sudanese runner Lopez Lomong, who went from running to save his own life to running to save others.