Why endurance runners should practice race day nutrition in training

Race day nutrition for runners

Whilst runners naturally focus a lot of attention on endurance running sessions, often less attention is placed on practising race day nutrition in the build to important long-distance races such as marathons, or ultra marathons.

As an endurance athlete you’ll know the importance of using good nutrition strategies to maximise running performance. Whether this takes the form of energy gels, energy drinks, or foods like a banana, or energy bar, the consumption of regular carbohydrates and sufficient fluids will help to delay fatigue, reduce muscle glycogen depletion, and significantly enhance running performance. However, whilst there are clear benefits to race day fuelling strategies, for some runners there can be a downside in the form of gastrointestinal problems, which can seriously impact running performance.

You may be less aware that you can actually train your gut to become more efficient at absorbing key nutrients and better able to tolerate the consumption of gels and fluids whilst running.

In this post, we’ll firstly take a quick look at how gastrointestinal (GI) symptoms and efficiency is impacted by running, and then move on to the importance of practising race day nutritional strategies in training, looking at how:

“nutritional familiarization, or, pre-race nutrition practice, should be considered an important training method for all long-distance runners.”

Running, nutrition and gastrointestinal problems

Gastro-intestinal problems are common during endurance sports – especially during endurance running. Endurance runners can experience gastrointestinal symptoms for several reasons. In some cases, the symptoms may be due to intolerances to certain foods, or certain nutritional products, especially if they are a new, or unfamiliar product. However, the two main causes of gastrointestinal symptoms induced by running, are believed to be the mechanical jarring action of running, and the effects of reduced blood supply to the gut – this occurs due to a natural diversion of blood supply away from the gut, and towards the working muscles.

Not surprisingly, as race duration increases, there is an increasing risk of gastrointestinal problems, in part due to the increased need for fluids, and or, energy gels or other foods. In addition, the efficiency of the gut to digest and absorb foods, and fluids, may become compromised. Whatever the cause, the results can ruin the most well prepared plans, and no one wants to invest so much time in the build-up to a key event, only to see it fall apart as the finish line approaches.

Importantly, gastrointestinal problems can be significantly reduced through a process of specific pre-race nutrition training.

The importance of nutrition training for runners

The process of nutrition training (nutritional familiarization) involves practising race day nutrition strategies during training. The aim of nutritional familiarization, or gut training, is to reduce gastrointestinal (GI) symptoms through familiarization, as well as training the gut to work more efficiently during running, and ultimately improve endurance running performance.

Endurance athletes include specific training sessions to prepare physically for the challenges of race day, but how many take the time to practice and familiarise themselves with race day nutrition strategies?

For all long-distance runners, it’s wise to practice race day nutritional strategies, as part of their build up to important endurance running races. Not only can this lessen GI symptoms and reduce the risk of suffering GI symptoms on race day, it can improve race performance, even amongst runners that don’t suffer with gastrointestinal symptoms.

Whilst some athletes test out nutrition strategies, or try out new energy gels or drinks during training, few will actually take time to regularly train their gut to become more efficient at digesting and absorbing food, or fluids. This idea might sound strange at first, but it’s no different to any other training, in that the more familiar, or the more you practice something, the more your body will adapt to it – the ability of the gut to efficiently digest food and fluids whilst running, is no different.

In fact, the gut is highly adaptable, and as such very trainable – more importantly research has shown that specific nutritional familiarization training (or GUT training) can actually improve running performance.

Research (1) has demonstrated that just two weeks of gut training, consisting of training whilst consuming either a carbohydrate gel, carbohydrate food, or placebo was enough to improve running performance by ~4-5% in the carbohydrate groups. In comparison, there was no improvement in the placebo group. In addition, two weeks of gut training reduced gastrointestinal symptoms, which in itself should be reason enough to practice nutrition strategies pre-race.

Training to improve gut efficiency when running

It’s very important not to wait until race day, or even race week, to practice, or test, a nutrition strategy.

If you’re racing focus is towards longer events, requiring within race nutrition strategies, like gels or energy drinks, then you should look to familiarise yourself with these routinely in training. This can be done over a period of months, with increasing frequency over the final month of training.

The best time to practise these is during longer training sessions, where you can practice and familiarise yourself with planned hydration and nutrition strategies. It’s also important to include some nutritional familiarization at goal race pace, or at a pace that is close to race pace.

If you’ll be relying on nutrition provided by the race organiser, then familiarise yourself with these and use these in nutrition training sessions.

Nutritional training during general phases of training:

Include nutritional familiarization sessions routinely, throughout general phases of training. For most endurance runners, one familiarization session every 2-3weeks should be sufficient. During this phase it’s best to incorporate these into longer runs.

Nutritional training in the build up to key races:

As race day approaches it makes sense to increase the frequency, beyond that seen during general phases of training. Including up to 2 nutrition training sessions per week, over the final 2-3 weeks before key races, will not only help to familiarise yourself with the nutrition strategy, it should help to improve the efficiency of the gut when exercising, which in turn reduces gastrointestinal symptoms. Additionally, the increased intake of carbs during these sessions will help to better maintain muscle glycogen levels, giving you the added benefit of improved recovery, and when combined with improved gut efficiency, and reduced GI symptoms this should ultimately improve race day performance.

One Important consideration

As with any type of training, the level of response, adaptation, and optimum frequency of these sessions will be highly individual – there will never be a hard and fast rule that can be applied universally for all endurance runners. As such, some runners may find that 1-2/weekly familiarization sessions is optimum during the final pre-race phase, whereas others may see more benefit from 2-3/weekly sessions. The only real way to know which is optimum, is to test these strategies out, and as always it’s preferably to test these strategies in the build-up to less important races.

Key points about race day running nutrition practice

  • Nutritional familiarization involves practising race day nutrition strategies during training
  • This helps to lessen and reduce the risk of GI problems when exercising
  • It’s beneficial for all endurance runners even if you they suffer GI symptoms
  • You should routinely incorporate nutrition training sessions throughout general training phases
  • Increase the frequency of these sessions over the final few weeks before a key race
  • Nutritional familiarization has been shown to improve long distance running performance and is beneficial to all endurance athletes

A Quick Summary of race day nutrition practice

Not only does pre-race nutrition training help to lessen GI symptoms, research has found this to be beneficial for improving long distance running performance. As such it should be considered an important part of the training process for all long distance runners and incorporated alongside other more established training methods.


Costa RJ, et al. (2017) Gut-training: The impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Appl Physiol Nutr Metab. 2017 May;42(5):547-557. doi: 10.1139/apnm-2016-0453. Epub 2017 Mar 22.

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