Yesterday was double run day. I've offen wondered why more people especially those who are not "runners" don't do it. It's a rather simple thought. Break the long run into two runs. The first being the longer of the two and the second to get blood pumping through tired legs without destroying those legs. The end result is high mileage without the huge tax on the system. Yesterday as an example was 90 minutes in the morning at long run pace. Not easy but absolutely not hard. In the evening Marco and I ran 30 minutes. The pace of the second run was faster but it felt easy and within 5 minutes the legs were fresh again. 2 hours of running for the day.
Waking up this morning my legs are ready to go if I want them to. I know most triathlon coaches put a bike after the very long run. I'll just say I learned this trick from someone who's won more Ironman races than any coach on the planet. I tend to side with results.