Well, I've had 3 of my team members go down in freak accidents last week. One simple tip over in a driveway and fracturing a humerous (requiring ORIF/plate screws). Freak fixie accident with broken skull, neck, clavicle (chain sucked up something), and a stick through the leg while cycling on a perfectly safe trail (Loveland bike trail) in a group. All experienced cyclists in their 40's. Though you might enjoy these couple :)
BE SAFE out there!
Fatigue is biochemical, not biomechanical.
- Andrew Coggan, PhD