One-day races and Classics Gert-Jan Theunisse (born 14 January 1963) is a Dutch former road bicycle racer.

[1] Theunisse returned the following year and won the mountains classification and the stage up Alpe d'Huez in the 1989 Tour de France .

[4] He began advising Mario Gutte and then mountain biker Bart Brentjens from late 1995.

In January 1999, he won a mountain bike race in the United Kingdom but could not walk for three days afterwards.

[7] He competed from 2003 to 2005 despite consistent pain due to spinal damage, difficulty walking straight as well as involuntary muscle or spastic attacks.

Theunisse was sponsored by PowerPlate-Giant and concentrated on the mountain bike marathons of the World and European championships.