How To Eliminate Gastrointestinal Issues On The Bike

Carbohydrate intake on the bike during rides that are 2+ hours long is a key nutrition strategy for enhancing performance and delaying fatigue.

Current guidelines recommend intakes of up to 90 grams an hour for rides longer than 2.5 hours in duration using multiple transportable carbohydrates, with growing interest in intakes as high as 120 grams an hour in a bid to maximise carbohydrate availability and performance (although not something we’d currently recommend for most athletes at Fuel The Ride Academy, might I add).

Whilst these strategies may be beneficial on paper and in the lab, the application of these strategies on the bike in the real world can be significantly challenging. One of the major challenges we face when trying to fuel, particularly at high intakes of carbohydrates, is our digestive systems’ ability to comfortably tolerate the fuel without inducing debilitating stomach issues that can negate the benefit of consuming the fuel in the first place.

Exercise and competition, in particular, put the digestive system under significant stress. It redistributes blood flow away from the gut to the exercising muscles, negatively impacting the gut's ability to digest food and disrupting the nervous control of the gut. These factors can both lead to exercise-induced gastrointestinal syndrome.

Exercise-induced gastrointestinal syndrome induces symptoms that can range from short-term acute effects like bloating, nausea, belching, regurgitation, pain, and heartburn to flatulence, urge to defecate, lower abdominal bloating, diarrhoea, blood loss in stools, and loose stools right through to chronic, more serious conditions like ischemic bowel disease. These symptoms won’t positively impact performance and are best avoided.

Whilst carbohydrate intake during exercise can help support the gut by maintaining blood flow and preventing issues, poor tolerance to high carbohydrate intake can be a significant problem, but we now have tools that we can use to help deal with these issues.

In recent years, we’ve come to learn that, like many organs within the body, the digestive system is trainable. Our ability to tolerate feeding during a ride can be significantly enhanced through repeated exposure to gut training challenges during training (i.e. feeding and drinking in a way that will stress the gut), which can induce adaptations within the gut that can help improve our tolerance.

Through planned, structured gut training, we can significantly improve our feeding tolerance on the bike and significantly reduce the chances of suffering any of these issues ahead of key rides/competitions.

Whilst this area of research and practice is still very young, and we have a lot to learn, a recent review of the research (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10185635/) has given us great insight into the current evidence to demonstrate the effectiveness of gut training.  

Of the eight studies included in the review paper, they showed significant improvements in participants tolerating the gastric load, meaning the athletes experienced significantly less gut discomfort after the gut training/feeding challenge protocol they were subjected to and also reduced malabsorption of carbohydrates. They also observed reduced incidence and severity of exercise-associated gastrointestinal symptoms, particularly in the upper part of the digestive tract. This could lead to improved feeding tolerance and enhanced performance when implemented in the field.

If we take a more detailed look at one of the first-ever research studies investigating gut training (see here: https://cdnsciencepub.com/doi/10.1139/apnm-2016-0453). They took a group of well-trained runners and had the run on a treadmill ten times over two weeks; during each trial, they ran at 60% of their VO₂ Max’s for two hours whilst consuming either water or 90g/hr of glucose-fructose before completing a 1 hours distance test. In just two weeks and ten training sessions with feeding, they saw more than a 40% reduction in overall gut discomfort and total and upper- gastrointestinal symptoms in the group consuming the 90g/CHO/hr trial compared to no changes in the water placebo trial. It is a pretty mind-blowing change for a relatively easy-to-implement intervention that could have huge significance for future events.

If you want to develop a solid fuelling and hydration strategy to help you perform at your next events, it’s imperative to implement gut training as part of your event preparation to ensure an effective strategy.

We have a detailed lecture on how to prevent gastrointestinal distress on the bike within Fuel The Rice Academy, along with experienced coaches on hand to help you develop your own gut training protocol ahead of your next key event.