Runner’s trots, runner’s tummy, jogger’s bowels (I may have made that one up…) – whatever you want to call it, the issue of bowel disturbances as a consequence of running (and indeed other forms of exercise) is something that troubles a lot of runners – up to 70% of regular exercises have reported problems with diarrhoea, bloating, cramps, flatulence and nausea.
The extent of the problem can vary dramatically between people, from a touch of nausea after a run in some, to I Must Find a Toilet THIS INSTANT! severe diarrhoea in others. It can ruin training, scupper races and put people off being active.
So what causes it, and what can you do about it?
Identifying the cause of a problem is the first step in finding a solution. And in the case of exercise induced gastrointestinal disturbances, there can be several causes.
Potential cause number 1: The Gut
When you undertake sustained activity - typically 60 minutes plus, several things happen that can affect the way your gut works.
Firstly, when you start exercising, the way the blood flows through your body changes. The oxygen demands of the working muscles increases, and to meet this demand blood flow to the gut is reduced. And the longer you are active for, and the more intense the exercise, the greater the degree of the reduction in blood flow to your gut – some research has indicated that the reduction can be as much as 80% of the normal blood flow.
When blood flow to the gut is reduced, the motility (movement) and rate of absorption from with the intestines is affected. Movement through the gut becomes more sluggish, and ingested foods/drinks are more poorly absorbed than would be normal. This can cause GI symptoms including cramps, nausea, vomiting and diarrhoea – the typical problems we call Runner’s Gut (I may have made that one up too…).
Secondly, exercise can cause dehydration. Dehydration further reduces the flow of blood to the gut which can further exacerbate GI symptoms.
Thirdly, you get hot (even in British summer conditions!), and this - guess what! further reduces blood flow to the gut .
So lots of things going on in the way the gut is working.
When you consider putting something in to be digested – a gel, jelly babies, malt loaf, pork pies (or whatever your refuelling snack of choice happens to be) there's obvious scope for exacerbating tummy trouble in a system that’s functioning well below the optimum.
However - and here's a key thing to remember - one of the best ways to increase blood flow to the gut and to reduce some of the problems of dehydration, is to keep stomach volume relatively high. The more there is in the stomach (up to a point - you don't want to be gorging yourself!) the greater the flow of blood. The easiest way to keep stomach volume high and to reduce the effects of heat stress and dehydration is to drink. Water with added electrolytes as a minimum, but adding some carbs in will obviously help to keep energy levels up (either a sports drink or gels/dilute fruit juice/similar along with some water). If you do want to take on carbs - recommended for activity lasting 90 minutes or more - then you need to practise and train the gut to tolerate whatever it is you do to refuel.
Potential cause number 2: Diet
The foods we eat are an obvious area worthy of investigation when it comes to tummy troubles. There are some usual suspects, but the effect they have on people will vary – so some detective work is needed. The easiest way of doing this is to keep a food and symptom diary. You should soon be able to see a pattern if your symptoms always occur after eating a particular food.
So – the likely culprits:
Fibre is good for you. It typically comes in nutrient rich foods – wholegrain cereals, nuts and seeds, fruit and vegetables, it helps you to feel full, can help to lower blood cholesterol, and it’s good for the bowels.
But you can have too much of a good thing.
When you combine a fibrous diet (which gives the bowel a lot of work to do) with activity that reduces the efficiency of the bowel, then you’re almost setting yourself up for a problem. This won't apply to everyone - some people seem to be immune to tummy problems - but others will do well to avoid high fibre foods, particularly if you already have a history of conditions such as irritable bowel syndrome (IBS). Don’t cut fibre out altogether – see above for the health benefits! – but avoid high fibre meals in the 2-3 hours before training, and for a couple of days prior to a race if you are suspicious of fibre and its effects on your bowels. It’s certainly worth experimenting to see if there’s an improvement in symptoms.
Caffeine is well known for its pharmacological stimulant effects, but it’s perhaps not as well known that these effects extend to the stomach and bowels. As well as being a stimulant it is also an irritant, and it is quite common for people with IBS to be advised to reduce caffeine consumption. You don’t have to cut out caffeine altogether, but try avoiding it in the few hours before training and racing.
As an aside, caffeine is often consumed in the form of hot drinks, typically tea and coffee. Hot drinks are known to increase the speed of gastric transit – the speed at which things pass through the gut. Which is to be avoided if you have issues with diarrhoea!
Lactose is the sugar found in dairy products: milk, cheese, yoghurt, butter, etc. It is digested by the enzyme lactase, which is produced within the small intestines. Some people are deficient in lactase, and develop symptoms such as abdominal pain, bloating and diarrhoea after eating foods containing lactose. Most people can tolerate small amounts of lactose, even if they are lactose intolerant – it takes a little trial and error to work out your own tolerance level. If you are sensitive to lactose, avoiding it before training and races is recommended.
Not a term that most people are familiar with, FODMAPs (Fermentable, Oligo-, Di, Mono-saccharides and PolyolS) are forms of carbohydrates that some people have trouble digesting. They pass through the intestines and are fermented in the large bowel, causing typical symptoms of bloating, cramping, flatulence and diarrhoea.
FODMAPs are found in a wide variety of foods, including apples, pears, stone fruits, honey, wheat, onions, beans, as well as in artificial sweeteners such as sortibol and xylitol, found in chewing gums and mints. It’s not advisable to restrict your intake of all of these without medical supervision – you’re likely to end up missing out on a lot of essential nutrients. Keeping a food and symptom diary can help you to recognise if particular foods are causing your symptoms, and you can use this to carefully amend your diet. It can also help a professional advise you on how to sensibly and safely control your symptoms and maintain a healthy balanced diet.
Drinks sweetened with high fructose corn syrup can be particularly troublesome for some people – check food labels and avoid if you can and if you suspect this may be a source of your symptoms.
Carbonated drinks can promote gas within the stomach and intestines, and this can obviously contribute to bloating, cramping and flatulence – best avoided if you suffer from GI complaints!
Well known for causing tummy troubles regardless of activity, some people are susceptible to the effects of hot and spicy foods. Best avoided, especially in the days preceding race day!
Potential cause number 3: Mechanics
Another thing to consider is the mechanical 'jarring' that comes from running. Some people seem to be more susceptible to this than others, and there's a school of thought that proposes having a strong core can 'buffer' the intestines. So lots of planks and the like may help – it certainly can’t hurt!
Potential cause number 4: Stress
The psychological stress of training and participating in races can have an unexpected effect on the gut: you may not consciously feel stressed, but it can show itself in the bowels. This may be made worse if you’re anxious about previous experiences of Runner’s Gut and are worried about the problem reoccurring.
Resolving this cause of diarrhoea/GI complaints is more complicated than simply avoiding a food – you need to relax! Find a way of avoiding the pre-event jitters that suits your lifestyle, and try not to stress about having to find a toilet or the problem will become self-perpetuating!
General hints and tips
- Avoid eating in the couple of hours preceding a race.
- Try to regulate your bowels – the term ‘bowel habit’ is used for a reason. We can exert some control over where and when we go to the toilet, so having a routine of opening your bowels can prevent unexpected urgency! As peculiar as it may sound, give yourself time to sit on the toilet and relax without fretting!
- Have a warm drink and exercise lightly to stimulate the bowels before your training session or race. Once you’ve been to the bathroom, head out and go for gold!
- Experiment with training at different times of day if you have the flexibility to do so. Training in the evening when you bowels have accumulated the day’s food and drink may make the symptoms of exercise-induced GI problems more likely to occur. Try training in the morning, or timing a training session after you usually empty your bowels.
- Avoid foods you’ve identified as causing symptoms.
- Stay hydrated.
- Stay positive – if you’re new to exercise it may take some time for your body to adjust. If it’s a long-standing problem, try some of the suggestions and try not to fret too much about it, it’ll only make things worse.
- Locate a toilet! If all else fails, knowing where you can access a toilet can alleviate the worry of having to find one in an emergency.
You may decide to try an over-the-counter anti-diarrhoeal medication, and these may certainly offer some relief from your symptoms. But take caution – regular use of such medications can promote dependence. Not in the sense of addiction, but in that your bowel will start to rely on the presence of the drugs and not function well without them. If you take them pre-emptively they can cause constipation. Medication is an occasional remedy, not a long-term solution!
A Rule To Live By!
If nothing else, please take this on board – do not try something new on race day. No new gels, no new sports drinks, sampling unusual delights from the breakfast buffet, whatever it is: DON’T DO IT!
Putting something unfamiliar into your stomach is a Very Bad Idea. If you want to use gels, sports drinks or the like, find a brand that you like and use it in training. You’ll soon know if it likes you back, or if it has you cramping and running for the toilet. A bit of experimentation is essential if you want to avoid problems on race day. Trying something new for the first time before or during an event is just asking for trouble.
If you know that an event uses a particular brand, test it in your training. If you like it, great. You’ll know that you can grab a bottle/cup from a drink station and not suffer any ill effects. If you don’t get on with it, take your own fluids/gels with you.
Finally – consider getting a check-up with your doctor. If you have a change in your normal bowel habits, or are concerned about any of your symptoms, it’s always best to get yourself checked by a doctor. This topic isn’t something to feel embarrassed about – be sensible and look after yourself!