OK first of all im normally a mtb rider and have done the odd mtb race and can ride for a few hours no problem.
Recently ive been doing more running and now training for a half marathon which is my main focus.
I'd really like to do some cx races and the odd mtb race this autumn/winter but without sacrificing any running.
so i need to do at least 3 runs and i'd like to do at least 1 ride a week to help improve my mtb/cx races.
My question is what kind of mtb/cx training would best benefit me if i can only do it once a week?