I was asked by one of Kakithoner about mountain biking (MTB). He was interested to racing in UTM homemade MTB race named Giant UTM MTB Quest on 8-10 April 2010. As an ex-MTB home champion for several races in UTM trails, I was seeing a challenge for me. Not a challenge as a 'race rivals' but as a trainer or sports science personnel.
I need a plan to transform this guy, from sub 40 minutes for 10km run, to be a mountain biker within timeline of eight weeks. As my reputation before, I made a transformation of 100meter sprinter to become Powerman Duathlon finisher (10km run-60km bike-10km run) back in 2005 within 6 months.
Multi sports athletes especially with non-cycling background are often criticised for their bike-handling skills, so he need to learn to ride on uneven mixed terrain and control the direction of the bike by moving a weight around can only be beneficial.
The secret is to start slow and build up. There's no need to go to the rock strewn slopes of some purpose built mountain-bike trail start right outside the door. Handling is a most important skills in mountain biking. Besides others basic skills he need to learn ultra fast and get on shape together with the bike.
As long as he got his stamina & able to put his heart race consistenly at 85-90% VO2Max, I'm really sure he can hammering the race trails as long as he managed to be on the bike all the way.