Low heart rate running has become very fashionable over the last few years, and I have certainly found it suits me. You can read more about it from Phil Maffetone here and about the 80:20 rule here. The essence of the low heart rate method is that you run lots of your miles slower, building up your engine and avoiding injury.
Today, with eleven fellow members of the Redhill Road Runners, I set out for a glorious three-hour, low heart rate run. Our route was almost entirely off-road, usually in mud, and occasionally in water. In addition to being a fan of approximately 80% of my running being low heart rate running, I am a fan of spending plenty of time on my feet, which is why I do quite a lot of three hour, or longer, steady runs.