balancing running and lifting?

So, I happen to be an ultramarathoner and a CrossFitter, with a weightlifting emphasis w/ my trainer since obviously I don't need the extra cardio.

I will agree that there is a tradeoff. I'd be better at either of those things separately if I'd give the other one up. But I can participate in both sports without any big problems, and I love the results I'm getting in terms of how I look and feel.

For me the running is far more important to me than the lifting, so I only CF twice a week, sometimes a third mini session at home of some pullups or pushups or kettlebell. I run 5-6 days per week. And as you'd expect, I'm a better runner than I am a CrossFitter. I am making strength progress though. A month ago I couldn't do pullups, and yesterday I did sets of 3; I've added 15 pounds to by back squat, 7 pounds to my strict press, and 20 pounds to my deadlift since 6 months ago.

Given my schedule, obviously I do run the day after weight training my legs, in fact I usually also run later that same day. My runs are slower shorter and more painful than they would be w/o the weight session. However I am convinced that the combination made my legs more fatigue-resistant and helped me power through a trail 50K last spring - I didn't have near the miles that I'd had in the past to prepare for that distance, yet my time was not that much slower than usual and I felt fantastic the entire time, barely sore the next day.