Go slow. Everybody knows that as you build up your long runs in marathon training you are supposed to run them SLOW in the beginning..eventually you can start to run parts of them at marathon pace, but you still run the majority of the miles at M.P + 20-45sec/mile or even slower.
That's not for me! That said, almost everybody I know has this little birdie in their head that says "Well, that's all well and good for everybody else but I am going to see if I can run them at race pace..if I can run 20 at race pace I'll be much more confident I can go all the way and meet my target of X:XX".
Why only 20 miles? In fact, some non-runner (or short-distance-track runners) will be shocked that one doesn't even run the full 26.2 in training. "How can you race 26.2 if you've never run that distance at all?!?"
Long runs are the foundation. If there is one thing that's really really important to enjoying a marathon it's mastering your long runs. If you don't learn to love your long runs you aren't going to enjoy the marathon. (duh).
So, why Go Slow?
The first thing we need to acknowledge is that distances beyond 20 miles are special in their difficulty. There are two main problems that don't occur in shorter distances:
1) Our bodies can't store enough glycogen to propel us the whole way.
2) "Normal" non-elite runners can suffer large reductions in running economy as we get tired and don't extract rebound energy...slowing us even more or taking even more energy when we don't have it to give. We can be very sore the day after because of the damage to the muscles after racing 26.2 miles.
Problem #1 is addressed by teaching the muscles in your legs how to metabolize the triglyceride fats that are stored there. The trouble is that the genes that enable you to do this are only turned on if you are not forcing your body to use glycogen...i.e. not running fast.
If you insist on starting your long run training at race pace, and continue on that way, you will never teach your leg muscles how to burn fat. You will be very fast at running 20 miles but hit the wall at longer distances.
If you slow down, your body can switch over and will gradually adapt. The good news is that once you get this adaption, it seems to take a while to lose it.
Once you have the adaptation, you can gradually kick up the pace and get both your speed and keep the fat burning.
Why not run 26.2 very slowly to get even more benefit? Because it's just too hard on your body. You get enough adaptation by going out to 20-ish...any more than that and you will be too sore to maximize your training for a number of days after that mega long run...you therefore you will lose speed. Years of experimentation by the elites teaches us schubs 8)
What about problem #2? Why does running economy suffer and what can we do about it?
There are two reasons running economy can go to pot as far as I have read..I will shorten and paraphrase.
1) The brain gets tired. Running is an amazing choregraphed dance of nerve firings to control hundreds of muscles from your big toe up to your head. As your brain get tired, the 'spark' from your brain gets weaker, and your ability to get power out of your muscles diminishes.
The classic example of this is 'bonking'. Usually bonking isn't running out of fuel in your muscles at all, its running out of glycogen for your brain. When this happens your "stride falls apart", you start to do more damage to your legs because of that, you get depressed and you have a very hard time continuing.
The brain, alas, can't be taught how to burn fat..it need high quality fuel: blood glycogen. It relies on the glycogen stored in the liver (limited to 100g or so) as well as sugars (drinks or gels) to power it during a marathon. Ultra runners talk about being completely spent and done..utterly unable to run and then getting a shot of sugar and caffeine and off they go again!
You need to fuel during a marathon to keep your brain happy and/or you need a little breakfast a few hours before your marathon to top up your liver glycogen. I have tried breakfast vs no breakfast and using GU and find if I take 1 GU every 30 minutes the breakfast can be pretty minimal (banana and bagel).
This 'brain strength' issue comes up in other areas too...we practice different running paces so our brains can learn the firing patterns and get them habitual. Those of you that complain "I just can't run slower...it seems so hard/uncomfortable/jarring/etc"..you need to practice it until your brain learns it.
Pylometrics (jump squats, etc) help develop a good mind/muscles connection ..trains for a 'hot' spark if you will.
Learning to run with both short compact, high turnover stride as well as a longer slower stride trains your brain and muscles to make you a more versatile runner. Different strides use different muscles and lets you get at more of the stored energy......unused muscles can't "give" unused glycogen or fat to other muscles during a race...it goes wasted. Being able to do other strides lets you harness all of it.
(This is perhaps why many runners say that a slightly rolling course is often one of the fastest..even better than flat. You get to use all your muscles.)
2) Not enough muscle.
Continuing on the above theme, another problem is that some runners have just barely enough muscle to do the job. They don't do sprints, strength training, core training or speedwork.
During a race your brain fires muscle bundles in rotation..a given bundle gets tired and it moves to a new one, then the next until it comes back around to the first set.
The more muscle you have, the longer each bundle gets to rest between firings (and of course you have more glycogen and stored fat) It's that simple.
So more muscle == less probability of hitting wall. Most beginner training plans don't include anything much other than long runs and that's good enough to get you to the finish, but perhaps not as fast as you could be.
I hope this helps explain why we do long run and other marathon training the way we do. In a future post I will do small reviews of the books I have read (where I learned all this stuff).
Some of the information learned in the last decade is pretty interesting...and shocking in fact!
Have a great long run!