Seko's notable marathon wins include Fukuoka Marathon (1978–1980, 1983), Boston marathon (1981, 1987), London Marathon (1986) and Chicago Marathon (1986).
On March 22, 1981 Seko set world records at 25,000 m (1:13:55.8) and 30,000 m (1:29:18.8). Both of these records stand as of 2008.
As of 2005, Seko is a coach at the S & B Foods Track Team, and a member of the Tokyo 2016 Olympics Advisory Panel.
The marathon is my only girlfriend. I give her everything I have.