running is hard on a ketogenic diet, i know because I've done it for 4 months at a time. For some reason though I prefer running at night and I'm really suprised how the body adapts to low carbs.
Be prepared to be much slower though; in a 5 day ckd diet, I'm much more fatigued and slow by day 3 due to carb depletion in my legs (I only run about 8miles a day tops).
a nice trick to keep you endurance is use ALA on the weekends and maybe one carb up in the middle of the week.
What I do is taper my running. For example, after the weekend, on monday, i'm full of carbs and I do about 50percent more mileage than on friday, when i'm ready for the weekend carb up.