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Training & Nutrition

Your Guide to Gastrointestinal Symptoms and Cycling

Do you get indigestion, flatulence, nausea or stomach cramps during a ride?

Gastrointestinal symptoms on the bike are quite common. Most of us have experienced some level of indigestion, flatulence, nausea or stomach cramps during a ride. For many, these problems are mild annoyances, but for some, they can cause misery. And no one wants to be miserable while cycling.

In order to try and help you understand why your body reacts negatively to doing exercise that is good for you, we spoke to dietitian, sports nutritionist and former international road cyclist and downhill mountain bike racer Danielle Clay. She helped us create this guide to what’s actually happening to your insides, and how to prevent those symptoms from ruining your day.

What’s Going On?

Although indigestion, flatulence, nausea and stomach cramps can be managed individually, the source of these varying kinds of discomfort originates for the same reasons.

When riding, physiological changes occur in the digestive tract as a result of reduced blood flow. “The blood flow is being redirected away from the digestive tract, as the body perceives it to be less of a crucial area,” say Danielle. “Instead, blood flow is focused on working muscles.”

This alters how your gut usually works. The movement of food through it will not be regular, which can lead to irritation and inflammation of the digestive tract.

There’s also a lot of hormones circulating, like adrenalin, noradrenalin and cortisol (stress hormones). These impact gastrointestinal motility too. The digestive tract also produces its own hormones and enzymes to cope with the stress you’re placing on it during exercise. This helps contribute to the general disturbances that cycling causes your digestive tract!

All this means there are changes in your ability to absorb nutrients and fluids, slowing down digestion.

The bottom line: Cycling freaks your digestive system out because the body re-routes blood flow to your exercising muscles and forgets about the bits that make you not fart.

The Symptoms: The Bottom Half

“Flatulence can be particularly problematic,” admits Danielle. “Gut bacteria have a greater opportunity to ferment any undigested food sitting in the intestines. A consequence of this fermentation is excessive gas.”

Also, Danielle can confirm the great news that symptoms like flatulence “appear to be more common in women and younger athletes and when dehydrated or if a meal has been consumed 3-4 hours pre-exercise.”

We’re not entirely sure how it’s possible to not eat for 3 hours, but this information may be useful to those of you with self-control.

Endurance cyclists also appear to be most at risk, and that’s not improved by the foods and drinks consumed during training and competition. Gels and energy drinks can cause shifts in water out of the digestive tract to aid the absorption of sugars in the gels and drinks. This means that you can mainline that saccharine sweetness, but it causes further disruption in the digestive process.

Unfortunately, many cyclists have symptoms that go further than flatulence. “The true aetiology of diarrhoea in cyclists is not fully understood,” says Danielle. “It appears to be more common in runners than cyclists, but again the general consensus is that it is also related to intestinal irritation.”

The Symptoms: The Top half

Interestingly, the reason cyclists are more likely to have digestive problems in the upper half of their digestive tract is totally down to mechanics: bending at the torso means you’re putting pressure on the oesophagal sphincter (“the valve between oesophagus and stomach” – thanks, Danielle).

This causes stomach contents to be pushed back into the oesophagus, giving cyclists acid reflux or even causing them to vomit. Obviously, these symptoms are not helped by the changes in blood flow discussed earlier.

Managing Symptoms

“First and foremost,” says Danielle, “if symptoms are persistent and severe, they should be fully investigated by your G.P to rule out any medical issue.”

If you’re given the all clear, or your issues are mild, try some of the following steps recommended by Danielle to improve your time on the bike:

1. Stay hydrated. Ensure you’re well hydrated before training, and experiment with different sports drinks during training to find one that suits you.

2. Evidence suggests drinks containing fructose can aggravate digestive issues more than glucose, sucrose or maltodextrins. Avoid drinks containing fructose, and read the labels of the products you are using.

3. Avoid large fatty meals within three hours of riding.

4. Research consistently finds that glucose polymer drinks (sports drinks) mixed with a 6-8% solution are optimal in terms of absorption of energy and fluid from the drink. However, the more glucose that’s contained within the drink, the slower the emptying time from the stomach to the small intestine. Therefore, consuming a glucose polymer drink that is less concentrated may help with symptoms.

5. Look at your position on the bike. Are your handle bars too low? Do you try to take regular breaks out of the saddle to improve posture?

6. Some individuals may find antispasmodic medication or medication to reduce production of gastric acid to be beneficial, however, these should only be used under the supervision of your doctor.

7. Prolonged irritation to digestive tract can lead to a condition known as dysbiosis, which is an imbalance of the friendly bacteria in the digestive tract. A good quality probiotic supplement regimen may help with symptoms.

If all else fails, speak to your health case professional, consult with a sports nutritionist or sports dietician like Danielle.

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