I'm looking for opinions re long runs as it relates to marathon training: Is it better, worse, or same as, to replace a 20 mile run with 16 miles one day and 5-6 miles the next?
I've done both, and there are good reasons for both, but I'm interested in other runner's opinions.
I like doing the 20 mile distance because I think that it helps build endurance. The downside is that the opportunity for injury increases with high mileage like that. On the other hand, I can run a 16 miler a skooch more aggresively, with less risk of injury, and then run another 5-6 miles the next day.
But I wonder if I get the same benefit (endurance-training) from doing the 16/5 miles split vs banging out a full 20 miles at one whack.
There are differing opinions on this sort of thing. I have read, in the past, that once you hit 16 miles, more doesn't make much difference. I haven't read it lately and I'm not sure how true it is. A lot of coaches think that LSD is key to marathon training. Some even the farther the better - Galloway for instance. On the other hand, the Hansons I think, advocate that running up to 16 at close to marathon pace is good preparation.
Regarding "divided" runs: I'd asked a related question several years ago while training for my first marathon. The general consensus of the responses (from people who are a lot more experienced at marathon distance than me) was that there is simply no substitute for a long continuous run. Dividing the long run into two parts will give you the same overall mileage, but it will not prepare you for running in a state of near-total or total glycogen depletion (20 mi is fast approaching the Wall) or for the sheer stress of pounding your body and being on your feet for 20 mi straight.