Saturday, April 6, 2013

Stomach Issues in Ultramarathons (or: Another Easy DNF Fix)

A few weeks ago, many of my friends attempted the 100K and 100 mile distances at a race in Wisconsin. More than a few of them DNF'd partly because of 'stomach issues', which is honestly a common DNF reason. While many people who run hundos train their legs for the race, they do not train their stomachs. I offer the following suggestions to make race day easier on your tummy.

Anyone who knows anything about marathons has heard of the dreaded ‘bonk’ which happens to many a rookie marathoner ,usually around mile 20. The cause is pretty simple to understand and involves how many carbs you can jam into your body.

Your body converts the carbohydrates you eat into stored glycogen in your muscles. Even if you are a large person, it turns out you can only pack about so much into your muscles before they are ‘full’. Depending on who you ask, this is about 2000-3000 calories. This fact is why marathoners will ‘carbo-load’ before a big race packing that glycogen in as tight as possible. It is also well known how much energy it takes to run 26.2 miles, which is (amazingly) about 3000 calories. What that means is that most marathoners who carbo-load and/or take only a small amount of carbs during the race have little problem getting to the finish line.

When you ‘bonk’ you have run out of glycogen and while your muscles are trained to use that as their primary fuel source, your brain also needs it. When it runs out, your brain goes foggy. Bonking is a physical and mental problem. Your body does have a backup system to keep you from dying and that is the fat you have stored. And there is a lot.

In ultramarathons of 50 miles and longer, life is much tougher than a marathon. Even if you jam 3000 calories into your muscles the days before, you are gonna burn through that in the first half of a 50 mile race. That means you are going to need to consume a few thousand calories during the race to prevent bonking. For a 100 mile race it is even more.

Getting all those calories via liquids (gels or XYZ-ade) is generally not enough as they are not that calorie dense. This is why most ultramarathoners consume solid food during their longer races and why aid stations are usually stocked with all sorts of delish solid foods which generally have oodles of calories per serving.

Your stomach, however, is not built to process solid food while you are running. Think ‘fight or flight’. You are definitely ‘flighting’ while running so your insides are busy converting stored energy into usable energy. When you consume solid food while running you are asking your body to suspend that (important) process to do something very different, convert consumed food into stored/usable energy.  This is why right after a big meal you just want to sit, not go for a run.

And that is why (I posit) that many people get stomach issues that slow them down and/or cause a DNF in an ultra. I further propose that these issues can easily be solved with simple training, and you don’t even have to become a ketogenic athlete to do it, but of course that would be best :)

The first solution is simply training your body to consume solid foods while running. I know, I know, it sounds simple, but it is commonly overlooked by ultrarunners when training. When they are doing their long runs (generally 20-30 miles) they run it like running a marathon, having a good dose of spaghetti the night before and consuming gels and energy drinks during their run, and very rarely attempting to eat solid food, simply because they don’t have to eat solid food to get through that workout.

I am a huge fan of the concept ‘train as you fight’ which means you want to train your body both physically and mentally for as many race day issues as possible beforehand. That means you need to practice eating on the run, but more importantly, you need to practice eating solid food when your body needs it.

Again, if you are running 20-30 mile you can get away with only liquid fuel during the run because your body has a good chunk of glycogen stored because of your normal diet. So, let us remove that. You need to start your long run depleted. The day before a long run, avoid carbs, in fact, maybe even skip dinner and go to bed hungry. Wake up, have your coffee and then go for your run. You will run out of stored fuel quickly maybe only 5-10 miles, which is what you want. You have just put your body (mentally and physically) in the same boat you will be in at mile 40+ and you didn’t have to run 40 miles to get to that point.

Now, as you are hungry and running is when you start testing your foods. Yes, you are testing, because we are all an experiment of one. You want to try every solid food you have ever heard of people consuming during an ultra. Jello. Beef Jerky. Hard-boiled eggs. Cookies. Gummi worms. Fruit. PB&J. Grilled cheese. Spaghettios. You are testing different thing to find out what YOUR body can handle under those conditions, and more importantly what your body cannot handle. When do you want to find out that food X makes you want to vomit, during a 20 mile training run or mile 60 of your first Hundo?

I know in my training, I figured out (after 5 Hundos) that I did best with fresh fruit. It is a simple food and my stomach has little problem breaking it down while running. The more ‘complex’ the food (read: processed) generally the harder it is for your body to break down. So chocolate chip cookies might look good and taste good, but there is a good chance your stomach will reject them.

The goal here is to get a list of things you can and cannot eat. You avoid the cannot foods at aid stations and you pack your drop bags with the can foods. It’s really that simple, but not as simple as the other solution, which is training your body to not need as much solid fuel to make it to the finish line. Burn the fuel you have on board, fats.

As I said earlier, we can only store 2000-3000 calories as glycogen in our muscles, but we can store (depending on who you believe) 40,000+ calories of fat energy in our bodies. You have plenty of fuel on board, but your body is not used to using it.

You are born with the ability to burn carbs or burn fats. In modern society, we consume plenty of carbohydrates to get us through our day so our bodies rarely have to use fats as a fuel source. Your body can make the switch of course, the most obvious instances being when you bonk in a race (you don’t keel over and die right then) or when you are stranded on a desert island with only water and you survive for a week or so with no food. In both cases, your body’s survival mechanism has kicked in. Your body loves you THAT much.

However, if your body is not ‘practiced’ in that using-fats-for-primary-fuel-source process the ‘shock’ of the transition is rough, especially when you are deep into a long race.

People who follow a ketosis diet actually exploit this fact and eat very few carbs. I am such an athlete. I have trained my body to burn fats as my primary fuel source from the get-go as I have no glycogen on board. In effect, my body ‘bonks’ about 0.5 miles into every run I do. Since my body has made the adjustment (which took a few weeks) it is little problem for me. The benefits are numerous, but I will not go into that here, you can read about it in my previous post on ketosis.

Most of my readers have no desire whatsoever to go keto, and that is totally cool, but you can still benefit from the concept. You need to train your body to run on fats when the need arises. Think of it as training the backup system ‘just in case’. If your body has never really used that fat-burning-system until you are at mile 50 of a 100 mile race, of course it is gonna be rough.

So how do you train your body to burn fats? Simple, do a carb depleted run (much like our first suggestion) but this time instead of consuming solid foods containing carbs, you simply drink water and make sure you are getting enough electrolytes. That’s it. You are trying to bonk and more importantly, you are running THROUGH the bonk with no carbs.

Its gonna be rough the first time, just like the first time you ever ran 15 miles without stopping, but like that workout, it will become easier every time you do it. And once again, on ultramarathon race day when you run out of stored glycogen (you will at some point, I promise) your body will transition over and start burning through the HOURS of fat energy you have stored up. You will probably be consuming carbs during the race, but the fat burning process is gonna help you go the distance.

Ultramarathons are tough, but when you recognize that your training has to be changed more than simply ‘run more’ you will have a much better chance of finishing. DNF’ing is to be avoided at almost any cost. But that is for another post...


  1. Interesting thoughts, I like the concept. I ran my first 50 miler last month and had no issues. I also fueled with fresh fruit. Mostly because it was refreshing. I think the reasons you stated above are the reasons I had no issues. Didn't even think about it that way. Thanks!

  2. I subscribe to the 'train as you fight' mentality. I want no unknowns on race day. For ultras, you have to be creative to mimic conditions so you can learn and solve issues BEFORE race day. Creativity does no mean it is hard. :)

  3. Thank you so much for this info. I have been struggling to find that balance as I embark on my "ultra" running lifestyle. This has been very helpful.