Generally I would recommend HIIT over LSD simply because it trains your anaerobic system to a much greater extent, which should be your primary focus for combative sports.
What's your present level of fitness? HIIT is generally more intense (part of the name, duhhh) and if your body is not used to weightlifting, HIIT will very likely hinder your gains. What I do now is usually perform LSD with a heavy day in the weight room, especially for squats and deadlifts, since it's easy to do on a treadmill, eliptical, or bike. I find it also greatly reduces my DOMS for the next day. Then I do HIIT on separate days.
But why only do running? You can certainly do bw intervals, burpees are pure evil and one of my favorite exercises, swimming now that it's summer, etc...