One of the biggest concerns among endurance athletes is gastrointestinal comfort while fueling during exercise. You can combat gastrointestinal upset through experimenting with different types of products, and by practicing your fueling plan regularly before race day.
Experiment with different types of products to see what sits best in your stomach. Everyone’s body is individualized, so there’s no blanket recommendation here. But a few tips…
- Certain people feel more comfortable using liquid sports drinks, as it’s easier to match up fluid, fuel, and electrolytes all in one product. This is practical for shorter endurance events, like those lasting for 2 hours. For long events, though, many athletes prefer using other sources of fuel so as not to have so much sloshing (particularly for running events). In addition, it can be difficult in longer events to focus only on sports drinks, as you may not be able to meet your hourly carbohydrate needs without a potential risk of overdrinking.
- Don’t create an overly concentrated sports drink (you know, like when you throw 2 scoops of drink powder into your water bottle rather than 1). The concentration of a sports drink impacts how quickly it can be absorbed in the stomach. Making it too concentrated can slow absorption, increase the risk of the “sloshing” feeling, and increase the risk of stomach upset. Follow the directions on the bottle - the manufacturers have taken the concentration into account when they recommend the mixing instructions.
- Be careful combining a solid product (like a gel or shot blocks) with a carb-based sports drink at the same time – it could create a too concentrated situation (as described above). This is relatively individualized, but there are a few ways to get around this issue if you've struggled with GI upset because of it. If you prefer eating a lot of solid products or gels during your workout, you could combine these with an electrolyte-only drink (in other words, you get your carbs from the product and not the drink). Or, have your solid product with some water and then switch back to your carb-and-electrolyte-containing sports drink afterward.
- I personally recommend avoiding products that contain sugar alcohols, as these can cause gastrointestinal upset in some people. Check your product or food labels for ingredients like xylitol, mannitol, or maltitol (all sugar alcohols have that –ol ending in their name). If you find yourself experiencing GI upset after using a product with these, those sugar alcohols may be the cause.
Lastly, remember this: Just like you have to train your muscles to run or ride or swim, you have to train your gut. This is why it’s important to start experimenting with your fuel choices early on during training. If you never fueled with any product during training, but decide to use them on race day – odds are you might experience some stomach upset. Instead, try your fueling options during training and choose one that you’ve found settles well in your stomach over time.
Factor #4: Practicality
Keep in mind the practicality of whatever fuel you choose. If you’re going to be doing a 3.5 hour endurance event, it’s probably unlikely that you’ll be able to carry enough drink with you to support your energy needs (unless of course you are using what’s available on the course and you’ve practiced with that during training – which is smart!). Along the same lines, gels are light and easy to carry but during a 6 hour event you may get tired of the super sweet flavor and the texture, so you may want to alternate with another choice. Think about how much of each product you would need to support the goal rate of 30-60 grams of carbohydrate per hour, and see if it’s practical to carry and consume that much during your anticipated training/event time.
Factor #5: Electrolyte content
You’ll also of course need to consider the electrolyte content of the products you’ll be using. The most important electrolyte to be concerned about in endurance exercise is sodium. Losing too much sodium during an event may put you at greater risk for issues like heat cramping (anecdotal, but may play a role) or early fatigue. It may also increase the risk of hyponatremia, a dangerously low drop in blood sodium levels that has serious consequences (fluid overload is the primary factor causing hyponatremia, but sodium may contribute to this as well).
The ACSM recommends consuming 500 to 700 mg of sodium per liter of fluid you drink during any exercise that lasts more than an hour. Most commercial sports drinks will replenish around this rate. Certain sports drink products (Ironman Perform, for example) have a higher amount of sodium. This could be valuable if you are a heavy salt sweater or if it’s an unusually warm day outside.
Be sure to carefully check other sports nutrition products or real food products you are going to use to see how much sodium is in it. Some are quite low. If you use one of these products during a 2-3+ hour event, and you combine this with only water, you may risk falling short in replenishing your sodium needs. There are electrolyte tablets or powders that can be added to plain water to supplement your use of solid products with additional sodium if the product itself falls short, or you can add a sprinkling of salt to your product/drink.
Factor #6: Personal Preference
Of course, to use any product, you’ll want to enjoy the taste and texture. Don’t force yourself to down something that isn’t appealing simply because you heard it was a good product. As an example, I absolutely cannot stand gels – that texture just makes me want to gag! But shot blocks, raisins, and sports drinks work fine for me. There are enough products and foods out there that can be successfully used without having to eat one you don’t like.
Pulling it all together
Evaluate each of these 4 factors, plus the other 2 we discussed in the previous post - and then practice, practice, practice! Use your fuel choice during long runs or rides in training, and then ask yourself:
- Did you feel energized during your workout?
- Did you hit the wall or bonk at all?
- Did this cause any gastrointestinal upset?
- Did it taste good?
- Could you see yourself using it during your event?
- Could you carry enough on the course to support your needs?
You may want to sign up for our free training and fueling log which you can use to record your experiences with your training/fueling to see what works best for you.
Share with us: What is your favorite product or food to use during endurance exercise?