Improving Gut Performance on Race Day

Improving Gut Performance on Race Day

By: Kim Mueller, MS, RD, CSSD

You’ve conquered 13.1 miles and are determined to carry the speedy momentum to a shiny new marathon PR only you are quickly greeted with bloating, embarrassing gas, and some pretty severe stomach cramps that has you doubled over on the side of the road at mile 14 rather than pressing towards that covenanted finish-line.

If this sounds all too familiar, you are not alone. Gastrointestinal (aka, gut or GI) disturbances, which can target the upper and lower abdominal wall (see table below), have been shown to impact nearly every runner at some point during a racing career. In some incidences, these disturbances can be so severe that the athlete has to accept a DNF rather than a finisher medal.

Common GI Disturbances

Lower Abdominal Disturbances	Upper Abdominal Disturbances
Diarrhea Gas Side aches Urgent need for toilet Intestinal bleeding Lower abdominal cramps	Nausea Vomiting Bloating Burping Stomach cramps Reflux/heartburn

Causes of GI Disturbances

While the cause of GI disturbances can be multi-faceted, it is thought that the primary instigator is an overall reduction in blood and oxygen supply to the intestines, also known as ischemia, manifested by the fact that other cells, namely the muscles, are also in demand.  Ischemia tends to be most pronounced in prolonged strenuous exercise. such as a marathon.

Other key contributing factors are mechanical and nutritional in nature.  Consuming too many foods high in fiber in the final few days leading up to race day as well as on race day, for instance, will leave residue in the gut and increase the likelihood of lower abdominal disturbances.  Similarly, meals heavy in fat and protein can slow digestion making them undesirable choices especially the night prior to and on race morning.  Failure to allow adequate digestion time prior to gun start can cause unpleasant burping and vomiting to occur early on. It is also common for runners to swallow some air when drinking from water bottles and flasks, increasing risk for stomach distress.  Consuming too much of any ingredient (carbs, electrolytes, protein, fat) without the right volume of liquid/water or just too many calories in general based on oxygen available for digestion during racing is similar to throwing too much food down your kitchen sink; it results in a clogged gut, delayed gastric emptying and a consequent cocktail of upper and lower GI disturbances. Gastric jostling on the run tends to exacerbate lower GI disturbances, especially gas and bathroom urgencies.  And, lastly, failure to stay hydrated does not help.

Prevention

While complete avoidance of GI disturbances in racing may be a challenge for some due to an apparent genetic component to such problems, the following strategies and nutritional practices can certainly help increase the likelihood of a happy gut on race day.

Gut Training Tip

Consuming carbohydrates in training at a rate of 30-90g/h, preferably from multiple sources (e.g., glucose + fructose), has been shown to increase the rate of carbohydrate oxidation due to enhanced intestinal absorption, helping to improve  nutritional tolerance as well as endurance performance.

Train the gut: Overall running performance is most certainly impacted by proper execution of race day nutrition. The problem is that many athletes focus all their attention on training and enter race day vastly underprepared on the nutrition front. Right off the bat, research supports the notion that athletes who fail to practice taking in fluids and nutrition in training are twice as likely to experience GI disturbances on race day compared to those who have practiced with their nutrition in training.  As a side note, if it’s not the same nutrition you plan on using on race day, you are not prepping your gut properly. At least once a month, try doing a mini race simulation where you practice EVERYTHING nutritionally from a timing, hydration, and fueling perspective at your target race pace.  It doesn’t have to be the entire distance of your goal race but it should encompass at least a portion of it.  Document your results in a training log so you can review what nutritionally has worked (or not) leading up to race day.

Follow a low-residue diet pre-race: For up to 72 hours pre-race, minimize residue in the diet (http://www.webmd.com/ibd-crohns-disease/low-residue-diet-foods).

Give yourself adequate digestion time pre-race: In general, allow approximately 1-hour digestion time for every 200-300 calories consumed, focusing on low-residue carbohydrates on race morning.

Avoid non-steroidal anti-inflammatory drugs (NSAID) and aspirin pre-race: Chronic use of NSAIDs and aspirin has been shown to damage the intestinal wall and increase incidence of GI disturbances.

Be careful about certain supplements: Several supplements and ergogenic aids, including caffeine at high doses, beetroot juice, and sodium bicarbonate, can increase risk for GI disturbances so be aware how your body responds to a supplement prior to implementing it on race day.

Stay hydrated: Sip on fluids so that urine runs pale yellow pre-race and water weight loss does not exceed 2% during racing.

Kimberly Mueller is a Registered Dietitian, Board Certified Specialist in Sports Dietetics, elite runner, author of The Athlete’s Guide to Sports Supplements (Human Kinetics, 2013), and owner of Fuel Factor (www.Fuel-Factor.com). She has enjoyed helping fellow runners dial in their nutrition and training for optimal health and performance for over 15 years. Contact her at kim@Fuel-Factor.com