I understand if you are doing a sub lactate effort your body uses predominantly fat as fuel. I have read that if you go above your sub lactate zone your body will use a different means of fuelling your muscles. I'm under the assumption that once your body starts to use this different source of fuel, that your body will not just switch back to using fat as fuel just because you reduced your intensity. If this is true would I be better served to do my sub lactate efforts first then do my harder intensity efforts near the end of my workout or am I separating my workouts to dedicated hard days and sub lactate days. I would like to mix them as there is not enough time in a week to fit in everything.