Friday, June 16, 2006

Now Back to our Regular Program

Lucas and I met for 8 miles this morning, and we spent some of it discussing me possibly putting on a 5K benefit run for Haiden's pre-school. There are some nice winding roads just east of where I live that could be perfect for a looped-course, low-key race , I just have to work up the courage to follow through with it. We started at an easy 8 minute mile pace, but gradually dropped the pace until we had averaged 7 minute pace for the duration.

The legs felt pretty good considering another night of poor sleep. Finn woke up twice and needed comfort, and Haiden somehow appeared in our bed at some point after midnight, which has never happened. She announced she was hungry and was going to make breakfast for the whole family. While it's good she has her appetite back, the timing of its return left something to be desired.

Speaking of food, Evan posted a link to this article on the how's and why's of "bonking" (American-style, that is). I found it to be a good overview of how food is absorbed into the bloodstream and converted into energy, as well as what foods work best and when. Sasha described what happened to me in the latter stages of my last marathon as a classic "bonk", and while I didn't want to believe it, this article's description of the brain's reaction to liver glycogen debt (the brain apparently only burns liver glycogen) leads me to believe he might in fact be on to something.

I've said before that the brain can betray the body, tricking it into slowing down before it has to. In the article a study is noted where athletes were driven to the point of exhaustion after four hours. Their muscle glycogen concentrations and carbohydrate burn rates were the same as at three hours, which defies conventional wisdom on blood lactate elevation and glycogen depletion. "The tradition in the science is, you hit the wall when you run out of muscle glycogen," says Dan Benardot, researcher and author of "Nutrition for Serious Athletes". But he maintains that the carbs stored in the muscles and bloodstream, along with the energy coming from fat, should supply the 100 extra calories per mile that a runner needs and then some, provided he stays aerobic. "When you do the math, there should be plenty of glycogen left in those muscles," Benardot says.

This is where the brain comes in. "It's a very interesting phenomenon that we're only now coming to grips with--that mental fatigue will lead to the perception of muscular fatigue," says Benardot. He notes that the brain has a lot of processing to do during a run, monitoring blood volume and sweat rates, core temperature, blood sugar, and stress hormones. "The brain is juggling all of this information and can eventually make the decision: 'Whoa, things are not good here, I'm going to shut it down."

So, did I just think I was tired? If I went anaerobic early, as Duncan suggests, then probably not. Going anaerobic too early in a marathon pulls the picnic blanket out from under the food, splilling everything and ruining any chance of optimally utilizing stored and available (on the course) glycogen. Chances are this was my downfall. Dehydration didn't seem to be an issue, as I did hit every water stop (though I did take mostly small sips and relied more and more on powerade and less on water as the race progressed). All right, enough obsessing already.

At the end of the article, which serves as an annotated history of optimal nutrition before, during, and after racing, the only concrete conclusion is something we all know already- any amount of dehydration adversely affects running performance and glycogen uptake. Nothing new, but worth repeating nonetheless.

Training: 8 miles, 7 minute pace

4 comments:

edinburghrunner said...

Nothing wrong with analysing the variables. Looking forward to seeing how you get on with the Chicago half.

angie's pink fuzzy said...

I read an article awhile ago mentioning the same idea - that the brain can lead you to believe that you are depleted, when if fact you are not (something about our evolution and needing to retain some energy to outrun the woolly mammoths that could charge us at any moment). I've often used this when I am exhausted in a long run - reminding myself that I have more reserves than I think I do. Interesting food for thought, anyway.

The Track & Field Superfan said...

This is exactly what Dr. Tim Noakes said a few years back and al lot of people geve him a lot of grief about it. Turns out he's totally right.

Did you think you were tired? Sort of. Tired is literally a state of mind, because exhaustion is something sensed in the brain rather than the body. You have no conscious control over whether your brain shuts your body down, however. And that's exactly what Noakes thinks happens; the brain senses we're pushing our bodies to levels that could do us permanent harm and reduces the amount of muscle available to send us down the road.

Greg said...

have you ever heard of Running Within? It digs into the mental aspect of running and while I think a lot of the book is kind of Stuart Smalley "I'm good enough" junk, there is some decent stuff in the book. Might be worth a quick read if you're really interested in this.