A fundamental function of your gut is to keep food moving in one general direction. Just like when nasty stuff comes up through the sink drain in your house, it’s usually an ominous sign when foodstuffs reverse course in your gut. To keep things moving in a top-to-bottom fashion, your gut relies on peristalsis and the opening and closing of its sphincters. The job of your lower esophageal sphincter, for instance, is to prevent chyme as well as chemicals and enzymes in your stomach from flowing into your esophagus. In a fairly large number of people, including athletes and nonathletes, chronic dysfunction of the lower esophageal sphincter leads to repeated reflux of food and gastric secretions into the esophagus. If this reflux is accompanied by a burning sensation in the chest, the term heartburn is used to describe the symptomology, which is how most people know they’re experiencing reflux while running. Regurgitation, on the other hand, describes a situation in which swallowed food makes its way back to your throat or mouth, giving you one last (unsolicited) opportunity to taste what you had for lunch.
All of us have undoubtedly dealt with reflux-related symptoms at some point, whether it was from eating too much food or from going horizontal too soon after feasting. For a significant number of people, however, these episodes transpire all too frequently, and said unlucky individuals have what’s known as gastroesophageal reflux disease (GERD). In North America, approximately 18–28 percent of people have GERD, with similar rates found in most other places around the globe.
When it comes to experiencing reflux during exercise, studies show considerable variability in its prevalence, in large part because the terms reflux, heartburn, and regurgitation are often used interchangeably. A survey of 707 marathoners found that 9 percent of runners felt heartburn during training runs. A similar result emerged from a survey of marathoners recruited from the 1986 Belfast City Marathon, with 13 percent reporting occasional or frequent heartburn while running. These estimates are oftentimes higher, though, when surveys use the terms reflux or regurgitation, which makes sense given that not every episode of reflux is accompanied by burning.
In terms of how it does its job, your lower esophageal sphincter controls the passage of foodstuffs by opening and closing via the manipulation of muscle tone. When your lower esophageal sphincter is functioning normally, it blocks foodstuffs from entering or leaving your stomach by increasing muscle tone. Obviously, it needs to relax and open when you swallow, otherwise food would be indefinitely trapped in your esophagus. To achieve this, sensory receptors in your throat communicate with a region in your brain stem that controls swallowing reflexes, and this signal is then passed to your lower esophageal sphincter, which responds by relaxing. After you swallow, your lower esophageal sphincter ceases its relaxation phase and reestablishes a level of tone that prohibits the movement of foods and fluids.
So what goes wrong with this process when you experience reflux-type symptoms? Well, it depends on the situation, but in many cases your lower esophageal sphincter spontaneously relaxes in the absence of swallowing; the technical term for this event is transient lower esophageal sphincter relaxation (TLESR). It’s thought that TLESR is a venting of excess gas from your stomach when it’s distended with too much food and air. This distension reflexively initiates TLESR, which some scientists suggest is a way of preventing gas from accumulating in your stomach or from entering your small intestine. This is also why you might have noticed that belching frequently accompanies reflux episodes.
Now that we’ve established some of the underlying physiology behind esophageal function (as well as dysfunction), let’s turn our attention to the effects of exercise. Studies unequivocally show that reflux events are more common during heavy exercise. In one study, cyclists had contractions and pH changes in their esophagi measured while they exercised under three conditions: 1 hour at 60 percent of VO2max, 45 minutes at 75 percent of VO2max, and 10 minutes at 90 percent of VO2max. (VO2max is the maximal rate of oxygen consumption that one can achieve during exercise.) Upping exercise intensity, particularly to 90 percent of VO2max, unmistakably reduced the frequency and duration of esophageal contractions and was associated with more regular acid reflux episodes as measured by an electrode. A second study published a year later by the same research group replicated these results in nonathletes. It’s still unclear how upping exercise intensity provokes reflux episodes, although there are several possible explanations. Reductions in gut blood flow may impair esophageal function and reduce normal peristaltic contractions. Likewise, relaxation of the lower esophageal sphincter or a heightened pressure gradient between the stomach and esophagus are plausible explanations.
Mode of exercise is another important factor influencing the risk of reflux. In a study published in the Journal of the American Medical Association, healthy volunteers experienced more reflux episodes while running in comparison to cycling and weight lifting, and the authors suggested that the jostling of running was the most likely reason for this observation. (It should also be noted that cycling in a hunched position could theoretically increase pressure inside the thoracic cavity and exacerbate reflux in some athletes.) In contrast, a different study of seasoned weight lifters, runners, and cyclists found the most reflux episodes during activity in weight lifters. The discrepant findings could be because the latter study used weight lifters capable of manhandling heavier loads, whereas the former study used people with variable exercise backgrounds. Lifting a heftier load raises pressure within the thoracic cavity, which can push food back into the esophagus against the force of gravity. Increases in pressure are especially pronounced when a person performs the Valsalva maneuver (attempting to exhale against a closed airway) while lifting.
Strategies for avoiding reflux during training and competition can be both nutritional and nonnutritional in nature. Regardless of the particular form, reflux episodes are common when exercise is performed within an hour or so of eating. So the simplest nutritional advice for preventing reflux is to steer clear of eating a full meal within one to two hours of exercising. Moreover, meals rich in fat are particularly effective at causing reflux, so instead of downing a bag of potato chips and a glass of whole milk one to two hours before exercise, perhaps you should opt for modest servings of carbohydrate-rich foods.
During competition, it may be helpful to choose foods and beverages that empty rapidly from the stomach given that any clogs in the system can exacerbate reflux or heartburn. Fatty and solid protein-rich foods are two obvious choices to limit, but you should also pay attention to the carbohydrate concentration of the drinks you consume. Beverages with more than a 10 percent carbohydrate concentration retard stomach emptying and cause more reflux. There are several other foods and beverages (some quite tasty) that can induce or exacerbate reflux-type symptoms and may be worth avoiding prior to and during exercise:
- Citrus fruits
- Acidic foods like vinegar and tomatoes
- Spicy foods
- Carbonated beverages
It’s important to keep in mind that every athlete is different in terms of what foods they can tolerate, so trial and error is a critical part of any plan for managing reflux symptoms. Non-nutritional approaches to avoid or control reflux during exercise include lowering the intensity of exercise and trying medication. Much like with nausea, reducing exercise intensity isn’t a winning strategy during competition, although it might be feasible during training. Drugs that suppress gastric acid secretion (ranitidine and omeprazole) reduce reflux during exercise as measured objectively through esophageal probes. Somewhat surprisingly, these reductions in acid reflux don’t clearly translate to less subjective heartburn while exercising, which is a bit puzzling to say the least. Despite a lack of high-quality evidence in athletes, some sportspersons do obtain relief by using these acid-suppressing medications. Even though versions of these drugs are sold over the counter in the US, be sure to consult with a healthcare provider before using them. (Note: some ranitidine products have recently been recalled because they were found to contain a known carcinogen.)
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One intriguing (yet unproven) strategy for reducing reflux while running is “zenning out,” known more formally as relaxation training. People with boatloads of anxiety are prone to chronic reflux symptoms, and a handful of experiments have even shown that temporarily inducing psychological stress in people with reflux disease aggravates their symptoms. Interestingly, the subjective reports of reflux in these experiments often occur in the absence of any actual pH changes in the esophagus, suggesting that the symptoms arise, in part, from activation of brain regions involved in the perception of gut discomfort. With that in mind, it may be possible for people with stress-induced reflux to improve their symptoms through stress-reduction interventions that aim to shift the mind’s focus.
In one study from the University of Alabama, subjects experienced fewer reflux symptoms when a stressful task was followed by a 45-minute relaxation intervention, which involved diaphragmatic breathing, alternating between relaxing and tensing 16 muscle groups, and saying the word relax with each exhalation. Notably, relaxation training decreased symptoms by about 50 percent in comparison to a control intervention that focused on educating subjects about GERD. Another study, albeit with only 19 people, showed that four weeks of training designed to change breathing from the chest to the abdomen reduced acid reflux and improved quality of life as compared to a control intervention. Overall, there’s considerable reason to think that pre-exercise interventions focusing on relaxation could prevent—or at least mitigate—reflux symptoms during exercise, especially in the context of stressful competition. This hypothesis is yet to be tested in athletes, though there is probably little risk to trying these interventions if you’re suffering from stress-induced reflux during competition.
Adapted from The Athlete’s Gut by Patrick Wilson with permission of VeloPress.