Quote Originally Posted by Fellhound View Post
Can't see how the flexibility of the shoe has much bearing on the speed of your foot strike, and on off road terrain, most of the time the surface is more likely to mould to the sole than visa versa. On harder or more gnarly terrain, protection is likely to be the more important consideration.

The obsession with flexibility comes from outside fellrunning, I would suggest..
Still totally disagreeing... run with stiff planks on your feet and your foot-strike will be slow, plodding and laboured. Flexible soles allow you up on your toes when climbing but the flex means that more of the sole remains in contact with the ground. The rest of the time a more flexible sole deforms to the terrain far better, a bit like running mtb or cross tyres at very low pressure. Best grip I've ever had was from Inov-8 BareGrips for this very reason.