[2][3] Janvrin is a 1988 graduate of Simpson College, an NCAA Division III school in Indianola, Iowa.

Janvrin won the decathlon at the 1989 Olympic Festival with 7,863 points held at Memorial Stadium in Norman, Oklahoma.

Janvrin achieved his then personal best result of 8,345 points at the USA Olympic Trials in June 1996 in Atlanta.

He finished fourth and his score was the most points for a non-qualifying athlete ever in the history of the event[4][5][8] He would not make the team for the 1996 Summer Olympics in Atlanta which consist of the top three qualifiers, Dan O'Brien, Steve Fritz and Chris Huffins.

Later that summer Janvrin would establish his all-time personal best of 8462 points at the Thorpe Cup, which is a decathlon meet between Germany and the USA, and was held in Edwardsville, Illinois.

[17] On August 24, 2005, at San Sebastian, he scored 8618 points in the Men Outdoor Decathlon to set the World Masters Athletics (WMA) record for the M40 age group.