Face it, exercising is much more fun when it's pain free, and gut comfort rates high on the list for successful training sessions. To get the most out of training, our bodies need to be well fueled, but how do we manage that when our stomachs seem to act up during training?
Abdominal cramping is just one of a handful of symptoms that collectively are referred to as exercise-associated gastrointestinal distress. For short, we'll call it GI distress. Symptoms can include heartburn, burping, flatulence (the scientific term for passing gas), nausea, vomiting, abdominal or stomach cramping, the urgent need for a bowel movement, diarrhea, and/or gastrointestinal bleeding.
If one or more of these symptoms has ended some of your competitions or training sessions early, or arrived with a vengeance within a few hours of crossing the finish line, you're not alone. In fact, these types of gastrointestinal complaints are very common among endurance athletes.
In this article we'll explore GI distress, which athletes tend to get which symptoms, what are likely causes, and most importantly, what you can do to steer clear of the problem and keep your gut happy.
GI distress is common and symptoms vary by sport
Frequency estimates vary, but GI distress during or just after exercise is more common than not. In a study of individuals who trained for 18 months in preparation for a marathon, 25% reported symptoms of GI distress during a 25-km race 12 months into their training, and 52% complained of distress symptoms during the marathon itself.
In a another study of well-trained endurance athletes, researchers asked the athletes to report whether they'd experienced symptoms of exercise-related GI distress during the preceding 12 months:
- Among runners, 71% reported lower GI tract symptoms, such as side aches, abdominal cramping, urge to defecate, and diarrhea. In contrast, 36% reported upper GI tract symptoms such as burping, nausea, and vomiting.
- Among cyclists, the incidence of lower and upper GI tract symptoms were similar, at 64% and 67%, respectively.
- Reports from triathletes confirmed the symptom patterns observed in runners and cyclists. During the cycling leg of triathlon competitions, lower and upper GI tract complaints were reported in 45% and 52% of athletes, respectively. During the running leg, lower GI tract complaints were reported by 79% of athletes, while upper GI tract complaints were reported by 54% of athletes.
In the most recent and largest study to date, elite and recreational runners competing in an event that included distances of 5, 10, 21, and 42 km, were asked to complete a questionnaire related to GI distress symptoms. A total of 45% of the runners had at least one GI complaint during their run, and almost 3% reported symptoms in the 24 hours after the competition. These findings indicate that GI distress is common across endurance sports, and that the nature of the symptoms tends to vary from one sport to the next.
What is the cause?
The causes of exercise-associated GI distress are not yet fully understood. But a variety of causal factors seem to be at work, including some that are inescapable and others that you can do something about.
Factors you can't control
The fact is that digestion is a process that takes place best when you're at rest. Exercise throws a wrench into the works.
When you're exercising, blood flow to the digestive tract is severely restricted, the gut may incur all kinds of mechanical trauma due to the motion associated with exercise, and there's a boost in the secretion of key hormones that increase gut motility — the process whereby the contents of the digestive tract are moved through the system. Together, these exercise-related changes can wreak havoc on the digestive process, resulting in the range of GI distress symptoms that athletes report. The evidence also suggests that the higher the intensity of exercise, the more disruptive it is to normal digestive processes and the greater your chance of suffering GI distress symptoms.
Although you can't really do much about the mechanical trauma or the physiological changes that occur in the digestive tract in response to exercise, understanding that these factors exist underscores the importance of making adjustments to those causal factors you can control.
Factors you can control
Digestion is the process whereby the food and beverages that you consume are broken down so you can absorb necessary nutrients and eliminate waste. If GI distress is making it impossible to be at your best during training sessions or competitions, altering what and how you eat and drink before and during training and competitions may be your best shot at a solution. If your stomach acts up en route, don't despair. Slow your pace, assess your hydration and carbohydrate status and focus on addressing which one may be contributing to the problem. More often, it is due to inadequate hydration and carbohydrate intake, but sometimes it can be from overdoing calories during the race. The following are strategies to consider:
Change your pre-exercise meal and snacking regimenIf you've got a sensitive gut, don't tax your digestive tract in the hours before exercise.
Helpful Food Strategies
- Consume your pre-exercise meal 3–4 hours before training or competing to allow more time for digestion to take place.
- Consume liquid rather than solid food as a pre-exercise meal. Solid food generally requires a longer amount of time to be digested and absorbed. A fruit smoothie and a meal replacement drink are good examples of liquid meals.
- Steer clear of high-fat and high-fiber foods in your pre-exercise meal. Fat and fiber are slow to digest and/or process. Stick to easy-to-digest carbs and a moderate intake of protein for your pre-exercise meal.
- For carbs and fluids as you near the start of training or a competition, use a well-designed sports drink, such as Ironman PERFORM™ sports drink, instead of fruit juice or a soft drink, which are typically too high in carbohydrate concentration.
- Consider whether caffeine ingestion is contributing to your gastric woes. For many athletes, some caffeine before and/or during exercise can provide a much-needed boost. But there are individuals who develop GI symptoms from caffeine. Experiment with and without caffeine during training sessions to see what works best for you.
Stay in your hydration zone
If you don't adequately replace the fluid and sodium you're losing during exercise due to sweating, you can become dehydrated. When this occurs, there is even less blood circulating to the digestive tract, and this can make the symptoms of GI distress even more severe. That said, don't push your fluid consumption during exercise to the point where large quantities of liquid are sloshing around in your digestive tract and making you nauseous.
Hydration Tips:
- Try to avoid losing any more than 2% of your body weight due to fluid loss during exercise. For a 150-lb (68-kg) athlete, a 2% weight loss equates to just 3 lbs (about 1.4 kg). Monitor the effectiveness of your hydration plan by weighing yourself before and after exercising.
- Use a sports drink to rehydrate with and minimize fluid loss during exercise. For training sessions or competitions that extend much beyond an hour, or any time you're exercising in the heat or humidity, a sports drink that provides carbohydrates, fluids, and sodium, such as Ironman PERFORM™ sports drink, is a better option than plain water when it comes to managing GI distress. There are a number of advantages. A sports drink not only provides carbohydrates to fuel your muscles; it also provides a carbohydrate concentration in the optimal range to minimize GI distress. The sodium and carbs in a sports drink cause the fluid in the beverage to be absorbed more quickly, so there is less fluid sloshing around in the digestive tract. The sodium helps maintain your drive to continue drinking fluids and helps you retain the fluid that you've consumed, so that dehydration doesn't exacerbate the already-significant reduction in blood flow to the GI tract. Finally, athletes freely consume more fluids when their hydration beverage is flavored, as is the case with a sports drink.
- Implement and refine your during-exercise hydration strategy during training sessions, and find that gut-happy medium where you're in your hydration zone and GI distress symptoms are avoided.
Consume the right carbs in the right amounts during exercise.
For endurance exercise of an hour's length or longer, consuming carbohydrates during exercise can delay the onset of fatigue. During exercise, appropriate carbohydrate sources are primarily sports drinks and energy gels taken with water. If chewing is feasible, sports bars and energy chews are options.
Fuel up for comfort:
- In the 2–3 days leading up to an event, eat simple. That means limit higher fiber foods, like beans, raw veggies, cooked corn, and 100% wheat bran cereals.
- When using sports nutrition products during exercise, consume those that offer multiple carbohydrate sources, such as PowerBar products featuring PowerBar® C2MAX (Ironman PERFORM™ sports drink,, PowerBar® Energy gels, PowerBar® Performance Energy bars, PowerBar® Fruit Smoothie Energy bars, and PowerBar® Energy Blasts gel filled chews). PowerBar C2MAX is an energy blend that features a 2:1 ratio of glucose to fructose. Each type of carbohydrate is absorbed via its own unique intestinal transport system. This PowerBar innovation allows carbohydrate fuel to be absorbed at a faster rate, without overwhelming the carbohydrate absorptive capacity of the GI tract.
- During endurance exercise lasting 1–2 hours, consume carbohydrates at the rate of 30–60 grams per hour. Refine your rate of intake during race-pace training sessions.
- During endurance exercise of 2–3 hours or more in length, consume carbohydrates at the rate of 45–90 grams per hour. Refine your rate of intake during race-pace training sessions.
- Do not try anything new on race day! No new food, medicine, gel, chew or bar. Practice fueling while you train.
Consume adequate fluids with your energy gels
Another option for rehydrating and refueling during exercise is to consume an energy gel followed by a few sips of water. Make sure to select an energy gel that provides sodium along with carbohydrates, such as a PowerBar® Energy gel. These gels provide the carbohydrate and sodium of a sports drink.
Gel usage:
- Consume a gel every 20–45 minutes during exercise, and don't skimp on water. Follow the gel with a few sips of water to help your stay hydrated.
Race Day GI Problems and Solutions:
| Problem |
Solution |
| Race day stress, anxiety |
Choose liquid meal rather than solids on race morning; use relaxation techniques |
| Too many calories before and during |
Stick with tried and true pre-race and race-day fueling strategies. Devise a plan, practice it in training and execute on race day |
| Excess caffeine |
Practice your race day caffeine intake in training to determine your threshold |
| High fiber |
Switch to low-fiber diet 2–3 days prior to race; use white breads, reduce raw fruit and vegetables and have more juices and processed low-fiber foods |
| Too high of intensity |
Too high of an intensity impedes the GI tract from functioning so you should race at the right intensity; slow down if you are going hard and having GI problems |
| Aspirin and NSAIDs (Advil, Aleve, Motrin |
Eliminate 2–3 days prior to race; only take during race if 100% necessary |
|
Many Iron Girl competitors experience GI distress at some point during their event. What you eat and drink before and during your event can help prevent gas, bloating, diarrhea, or other stomach woes that can make a long day longer with multiple porta-potty stops.
Rap it up!
To avoid race day tummy troubles be sure that you start your race with adequate carbohydrate stores. Being fully hydrated is key, as well as maintaining good fluid status during the race. The stomach and GI tract work best when there is some fluid and food in it at all times. Remember not to go out too fast, and if you're planning on using electrolyte supplements during the race, make sure that you have practiced with them beforehand so there are no uncomfortable surprises!
References:
Brouns F, Beckers E. Is the gut an athletic organ? Digestion, absorption and exercise. Sports Med 1993; 15:242–257.
Fallon K. Athletes with gastrointestinal disorders. In: Burke L, Deakin V. Clinical Sports Nutrition. 3rd ed. McGraw-Hill, 2006; 721–738.
American Dietetic Association; Dietitians of Canada; American College of Sports Medicine, Rodriguez NR, DiMarco NM, Langley S. American College of Sports Medicine position stand. Nutrition and athletic performance. Med Sci Sports Exerc 2009; 41:709–731
Topics:
Research, Competition, Endurance, Ironman, Performance, Training advice
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