Gut Training for Ultra Runners

I’m writing this post, as I recently had an amazing day at the Red Rock Canyon 100k, which I attribute to a new gut training protocol I used immediately before the race. I wrote a post on Instagram alluding to this a few days after the race, and so many people reached out to learn more about what I tried. I figured that I’d learned so much, and it worked so well, that it was worth a longer post on the topic.

The Bear 100: the perfect failure to finally start doing gut training

This fall, I added The Bear 100 to my List of Failures. Yes, failures are not as satisfying as those glorious days where it all comes together, but this particular race was a major learning moment for me. At The Bear, I was having a great day, but then stopped being able to eat anything at all – including Mr. Noodles or plain ramen – from about 40 miles. Not wanting to death march 60km through the freezing night to the finish on this occasion, I decided to call it a (great) day after 100km, and return to hang out with Julien and Luc in Logan.

The Bear was a perfect “failure”, because I eliminated many other issues, isolating that the only remaining thing was that I needed to figure out how to train my gut. I had trained extremely well all summer, stacking many high-volume weeks with significant vert, I had practiced with my race nutrition, and this time I even had my COROS arm-based heart rate monitor, to validate that I went out in a very sustainable zone 2, not going out too fast. In the past, whenever I failed at a long ultra, there were always so many variables to untangle, that it was tough to determine the exact cause. But this time it was very clear. Physically, I felt amazing, and had so much left in the tank. It was clear, my major limitation was my stomach, and/or small intestine. I’ve gotten nauseous so many times before, and this finally felt like the last straw. I either had to choose shorter distances to run away from nausea, or figure out a strategy to improve my gut’s ability to tolerate food during a long, long run. When there’s a will, there’s a way!

Here’s what the research says…

Naturally, I dove into the academic research, realizing that someone out there must have insights and answers. And luckily, I found a treasure trove of great information.

The research really highlighted that the gut is highly trainable, just like your aerobic system or your muscles. I’d heard this before, but now I was ready to listen, and to learn the best way of training the gut.

The paper that interested me the most was led by Ricardo Costa from Monashee University. Published in 2017, the paper is called Gut-training: The impact of two weeks repetitive gutchallenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance, and it’s available for free online.

This paper found significant evidence to support an “active” gut training protocol, in which participants consumed a high dose of carbohydrates during running. In this study, researchers initially organized a pre-study “gut trial”, to get a baseline of participants’ GI abilities. This consisted of a treadmill run while ingesting a high dose of carbohydrates. Participants first completed a 2-hour treadmill run at 60% of V02 max, while ingesting a 30g carb gel every 20 minutes. Researchers collected several data points during the baseline gut test, including asking participants about GI symptoms every 10 minutes. Participants then completed a first time trial, in which they tried to run as far as possible in one hour. (Ouch, I’m glad I wasn’t a participant!)

Following the gut trial and the first performance test, participants were split into two experimental groups and a control group. While the control group was given a placebo (a sodium saccharin solution that contained 0 carbohydrates), one experimental group was given carbohydrate gels (glucose/fructose-based), and another was given carbohydrates in real food form.

The groups then completed a two-week gut training intervention, in which they completed 10 training sessions over two weeks. In each session, they ran for one hour at 60% of V02 max, while consuming their assigned condition (placebo, gels, or real food carbohydrates) at 0 min, 20 min, and 40 min, equating to 90g of carbohydrates in 1 hour for the two experimental groups.

Following this, the study re-tested all athletes, doing the same pre-study two hour gut trial and the one hour time trial again, this time post-intervention. Reviewing the gut trial results, researchers found that both experimental groups (real food and gel-based carbohydrates) had significantly reduced GI symptoms from the baseline trial conducted before the gut training intervention, with over 60% of athletes in those groups reporting lower GI symptoms.

Even more exciting perhaps, is that they found significant performance improvements. In the post-study time trial, both the gel-carbs-based and the real-food-carbs-based experimental groups performed significantly better than the pre-intervention time trial, whereas the placebo participants did not. In addition, the gel-based treatment group experienced significantly lower nausea in the second, post-intervention gut trial than in the test conducted before the gut training.

Reading this study, I was instantly excited. The results seemed so compelling, and the whole protocol seemed so simple to try to imitate. I also naturally love the training process. Could I train my way through my nausea issues?!

Here’s what I did…

I had less than two weeks before my 100k race, so I modified Ricardo Costa’s study protocol given the limited time. (I didn’t want to do any gut training in the 3 days before the race, in case of GI issues or consequences.) I went on 4-5 “gut training” runs, using old neglected running foods and drinks that just sit in my closet.

Here is exactly what I did before Red Rock Canyon 100k on November 9, along with notes of how it went…

1. October 29, easy 13k trail run:
   • I set off with 4 (expired) Clif chomps (32g carb) & 2 scoops Naak watermelon drink mix (60g carb) within about ~250ml of water, for 92 gram carbs. I drank steadily, and ate a chomp at 0, 15, 30, and 45 minutes, so that I’d eaten and drinken everything within 50 minutes. I kept going for another 30 minutes, which was uncomfortable. Post-run I felt disgusting: super full and bloated, sugared-out, and kind of hypo-glycemic! I could not imagine eating anything more.
     
2. October 31, easy 10k trail run:
   • I realized that the Naak drink mix has a lot of protein, so I switched to Skratch high-carb drink mix instead. For this run I took a soft flask with ~250ml water and 5 scoops of Skratch high carb mix (71g carbs), plus 3 expired Clif Chomps (24g carb), for a total of 95g of carbs. Like last time I drank steadily, and ate a chomp at 0, 15, and 30 minutes. I ate and drank everything within 33 minutes of the run, and this time it was a remarkable difference from the first session: I felt good, not too full, and way better than the first session! I’m not sure whether I felt better because the Naak drink (from session 1) had all the protein in it, or if the gut training was already working…
     
3. November 1, easy 8k trail run:
   • I followed the same protocol as session 2, and was able to eat and drink everything within the first 35 minutes of the run. My notes from that session say: “Felt good! … this is going down well now. I’m feeling great!”
     
4. November 3, 19km / 2h13min long run:
   • for this run, I incorporated Gu Roctane, which I knew would be the on-course drink available at the Red Rock Canyon 100k. I had 92 grams of carbs in the first hour of the long run (5 scoops Skratch high carb drink mix in ~250ml water, plus 1 caramel GU gel), and then in the second hour, I had 82g carbs (1 scoop of Gu Roctane drink in ~250ml water to make it super concentrated, plus 1 caramel GU). I felt great on this run too!
     
5. November 6, 6km:
   • Okay, I honestly can’t remember if I did this 5th gut training run or not. Unfortunately I have no notes of whether I did gut training or not on this short run!

I didn’t modify my regular diet very much as I did this. The only change I made is that I usually eat a large post-run snack immediately after a run, and sometimes I was literally still full from the gut training run, so I sometimes skipped the post-run snack when I was really full – especially as I was tapering, and my volume was much lower than usual.

Note that I wasn’t necessarily trying to hit 90-100g of carbs for my race day nutrition plan. In fact, I planned to stick with ~60g of carbs per hour for my 100k. The reason I did this was to “overload” the gut, similar to how you’d train faster paces than you plan to run on race day, to raise your “ceiling” and what you’re capable of at your top end speed.

Race day verdict!

At the Red Rock Canyon 100k, I was able to put my gut training to the test. Incredibly, I felt amazing all day, with no nausea, no gut discomfort at all, even though I was running for nearly 12 hours! I ate:

-2 Timbits and either 1 Precision 30g gel, or 1 Maurten 40g gel per hour
-At 65km, I switched fully to Gu Roctane drink mix from the aid stations, after my 12th Timbit was no longer fun to eat :p

I was able to eat my target of 50-60g of carbs per hour for the entire day, and could have definitely kept eating and drinking for much longer. This was a first for me in a long ultra, as I’m someone who routinely struggles with nausea and vomiting… I used to say, “it’s the ugliest part of our sport!” But now, I feel like it’s avoidable with the right training! And of course, the ability to eat and avoid nausea is a huge performance driver in long ultras. I finished the race with a new course record, 1st female, and 2nd overall!

If you’re reading this, and if you’ve ever struggled with the misery of nausea while running, I think you should give it a shot… there is literally no downside, except for the cost of the many carbs you need to eat during the gut training. You can even make your own snacks and drinks to make it more affordable, grab a $5 Gatorade container, or do what I did, and use the neglected running foods and powders from the back of your closet! While the gut training I outlined above worked well for me, I think it’s worth experimenting to see what works best for you. There are also a few great podcasts that came out recently that highlight other approaches you can consider. Read onto the next section for links to those!

More resources

Recently, there have been a couple great podcasts on the topic of fuelling:

1. I did a full research summary about gut training as part of a research paper to renew my coaching certification. If you want to learn more, you can read that here.
   
2. Jason Koop’s podcast recently hosted a discussion on High Carb Intake for Ultrarunners, which has some great information throughout on gut training.
   
3. The Singletrack Podcast also recently hosted an awesome two-part podcast on nutrition, which had a ton of information about gut training as well. Check out The State of Ultra Running Nutrition with Vic Johnson Part 1, and Part 2.