Friday, 15 August 2014

Dodging the bonk

No, not that kind of bonk ... I'm talking about the other one ... the Wall ... the one feared universally by novice and experienced runners alike.

The one that can stop you in your tracks anywhere from about mile 15, although for most people it would probably come a little bit later at mile 17-18.

Basically, you just run out of energy. Sometimes it's your muscles that give up; sometimes it's your brain; and often it's both. 


Nothing left ...

Lie down on the pavement and give up ...

Talk to the little green men that have materialised apparently out of nowhere ...

I haven't been through it (yet) and I'm sooooo hoping I can avoid it. So I've been doing some research, because simply hoping that it won't happen to me is no way to give myself the best chance of enjoying my marathon without it.

As with all the running information I've looked at, there are many many different theories and bits of advice. How on earth do you gauge what's going to work for you? I'm going to pick a side that seems to make the best sense to me and then try some stuff out on long runs.

The following is a summary of a good article on the subject written by Paul Scott for Runners World back in 2007. It's the best I've been able to find yet, but I'm keeping my eyes open in case there's been any important breakthrough findings since then.

1) The carbohydrates you eat are almost entirely used as fuel by your body. Unlike protein and fat, they have virtually no other use. It takes about 10 metabolic steps to turn carbs into energy and 20 to convert fat, which can really slow you down. (I'm really not sure I can go much slower!)

2) Carbs pass from stomach to small intestine where they become glucose and are absorbed into the bloodstream and head straight for the liver. The liver holds on to about 100 grams which is enough to feed the brain for about 4 hours.

The rest of the glucose in the bloodstream is used as first choice fuel by the muscles. Second choice fuel is the glycogen which is already stored in the muscles themselves. 

Your muscles hold 300 - 400 grams of glycogen, but your running muscles only hold about 100 grams, which is enough for 2 hours strenuous running.

Once your liver and muscles are fully stocked, any surplus glucose in your bloodstream triggers the release of insulin, which causes the leftover sugar to turn into fat.

So, what we want to try and do is encourage our muscles to stockpile more than their usual share of glycogen in the days before the marathon.

3) Which brings us to carb-loading. Taper your training in the 2-3 weeks running up to the event so you are not depleting your muscle glycogen stores on long runs; and for 3-4 days before the event aim to get 75% of your calories from complex carbs.

4) The brain only burns liver glycogen and it can only hold enough for 4 hours. There's no way that's going to be enough to keep me sane on my 6 hour trek. Apparently, if I run out, it will take only 50 grams of carbs and 10-15 minutes to get myself back to normal. 

I think I'd prefer some preventative action though! I'm not sure I want to wait until it all goes wrong to try and do something about it.

It looks like a high GI snack just before the race will help get sugar into my bloodstream right from the start and because I'll be a bit active and jittery, I will apparently avoid the insulin spike.

5) Traditional advice has always been to eat simple carbs during exercise to keep the liver stocked to feed the brain and to spare the glycogen stored in muscles.

6) More recently, work has been done to investigate whether protein has a part to play. Protein actually helps with the process of restocking glycogen stores. It also stimulates insulin release, which reduces the release of the stress hormone cortisol and stimulates blood flow to the muscle. You have about 30 minutes after exercising to get a protein portion eaten that will give you a real boost replenishing your glycogen stores.

7) Studies on cyclists demonstrated that those consuming a 4:1 carb-protein solution could go almost a third further than those consuming a simple carb drink and nearly twice as far as those just drinking water. Does that follow for runners though? The researcher went ahead and designed Accelerade, which is the one sports drink promoted by Jeff Galloway, but it's got a pretty bad reputation for taste and some scientists have conducted studies showing that it makes no difference. I think I'll have to give it go for myself.

8) Drink little and often and right from the beginning. Even slight dehydration slows the movement of food from your stomach into your bloodstream. A good drink at the beginning will stimulate this movement from the start and then drink something every 10 minutes to keep the fluid flowing.

You can find the full article here. 

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