Born and raised in North Battleford, Saskatchewan, Gerein suffered a broken neck in 1982 while training racehorses. He first competed as a swimmer at the 1984 Paralympics in Los Angeles, but subsequently had his greatest success competing in racing events, winning seven gold, four silver and three bronze medals during his racing career. He retired from competitive racing after the 2008 Paralympics. Clayton later lived in Pilot Butte, Saskatchewan for a long part of his lifetime and career and was seen all around town practicing.