flightless wrote:
It's unfortunate that what I'm about to say has become [and I overstate slightly] a controversial opinion, but if you're training for a marathon one of the best things you can do is do all of your moderate-easy morning runs, including long runs, without eating anything beforehand, or taking on any calories during them.
If you can work up to running for 2.5-3 hours without eating anything beforehand, and taking nothing but water that is a fine place to start for then pushing down towards marathon pace, again without gels.
If you're going to use gels in the marathon, and I think they're something to try, you want to have used them 2-4 times in training on long runs to make sure they agree with your system. Some people have GI issues with gels, which is never great in a marathon.
But if you consistently use gels on long runs your body will never really get used to sparing glycogen.
Yes, it's painful at first to hit a wall in training, but think about it this way. Hitting the wall in training makes it less likely it will happen in a race. There's a sense in which you want to hit the wall a couple of times in training. The first time your body doesn't know what to do, that's what happened to the original poster. Most of the subsequent times it both responds a little better to running out of muscle glycogen, and pushes that point a little further out.
Obviously long runs without calories put some stress on the body, deplete muscle glycogen etc. It can take 48 hours to totally replenish. I can often feel the lingering effects of Sunday's long run on Tuesday's moderately long run. It's all good marathon training.
I'm also with Alan on the long runs without water in winter. If you can dress right, hydrate beforehand etc, winter is the time for the body to learn to run well with not much fluid intake.
I'd recommend these two articles as useful discussions of the issue. Mcmillan's is especially good, and makes suggestions for how to implement these ideas in your training.
http://www.mcmillanrunning.com/rununiv/marathonlongrun.htmhttp://www.runnersworld.com/article/0,5033,s6-51-0-0-6263-1-2X3X5X7X8X10-7,00.html
Sorry, but this idea of running on low energy makes no sense when you are not going to be racing in those conditions. Take in the energy to maintain the intensity to maintain the training stimulus not to mention that you wreck your training less on the following days.