(CNN) -- Jenson Button might not be having his best year on the race track, but it's been another notable year for the Briton competing in triathlon events. What started out as a way of keeping in physical and mental shape for the rigors of Formula One has turned into serious hobby for the 2009 world champion, earning him -- at the age of 34 -- the distinction of being called the fittest man in the pit lane. In July, Button hosted his third annual charitable triathlon at Luton Hoo Estate in Bedfordshire, raising a "huge amount" for Cancer Research UK, and last month he finished 11th out of 1,675 competitors and second in his age group at an Ironman event in the Philippines.
@highlight
McLaren driver seeks fitness expertise from advanced sports lab
@highlight
GSK Human Performance Lab helping unravel secrets of elite performance
@highlight
McLaren driver tests fitness against pro triathletes the Brownlee brothers
@highlight
Button has some of quickest reactions ever shown at London-based lab
All of which makes Button -- who is seventh in the F1 drivers' championship with just one podium finish all season for his @placeholder team -- one of the most famous amateur triathletes in the world.