ReFuel WINTER 2018 - Page 15

ACHIEVE PERSONAL BEST PERFORMANCE

Nutrition and exercise related strategies for optimal gut health and performance

Y ou are on track to run a PB when halfway

through the marathon the nausea starts , and then the vomiting . You can ’ t take in any fluids or nutrition . You are in shape to run a PB but your race turns into a struggle to make it to the finish line .
You might be surprised to learn that you are not alone . Gastrointestinal symptoms such as bloating , nausea , stomach pain , vomiting and diarrhoea ( also called the runner ’ s trots ) are quite common during running . They affect at least 60 % of endurance runners and can have a detrimental effect on nutrition intake , training , race performance , and recovery from exercise .
SO WHAT IS IT ABOUT EXERCISE , AND IN PARTICULAR RUNNING , THAT CAUSES THESE GUT ISSUES ?
During exercise blood flow is diverted away from the gastrointestinal system to the working muscles . This reduction in blood flow , an increase in stress hormones during strenuous ( e . g . high intensity ) and prolonged exercise , and the high impact nature of running can cause damage to the gastrointestinal tract and impair digestion and absorption of ingested food and fluids . Exercise-induced gastrointestinal symptoms may therefore develop as an outcome of altered digestive function and / or damage , or arise due to the ingestion of food and fluids which are not easily digested and absorbed . Dehydration , exercise in the heat or exercise that causes a high core body temperature can also cause gut issues due to a further reduction in blood flow to the gastrointestinal system , increase in stress hormones and altered digestive functions .
HOW DO YOU BEST PROTECT YOUR GUT DURING EXERCISE ?
The following exercise and nutrition related strategies aim to protect your gut by minimising the previously mentioned stressors :
Exercise related strategies ¾¾
Race-specific exercise training .
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Maintain an appropriate pace / intensity to keep heart rate and core body temperature below the threshold for symptom development .
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Undertake heat acclimatisation prior to competing in the heat .
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Use pre-exercise and / or during exercise cooling strategies ( e . g . ingest ice slurry or cold fluids , apply ice packs / vest , cold water immersion etc .) in the heat to limit the rise in core body temperature .
¾¾ Use the bathroom before exercise .
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Avoid using non-steroidal anti-inflammatory drugs around exercise .
Nutrition related strategies ¾¾
Commence exercise hydrated and maintain hydration through fluid intake , but avoid excessive fluid intake which can also cause gastrointestinal symptoms and hyponatraemia .
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Train with nutrition to ‘ train your gut ’, improve tolerance to food and fluids and establish an upper limit for carbohydrate and fluid intake .
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Consume food and fluids in small amounts frequently during prolonged exercise rather than large amounts .
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Consume carbohydrates at a concentration of < 10 % to optimise emptying from the stomach and absorption ( e . g . consume at least 250ml of water with a gel containing 25g carbohydrates ).
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Limit pre-exercise and during exercise intake of fat , protein , fibre , caffeine and fermentable oligo- , di- and monosaccharides and polyols ( FODMAPs ).
An Accredited Sports Dietitian can assist you with planning a tailored program to avoid gut issues . If gastrointestinal symptoms occur in the absence of exercise or on a daily basis then it may be worth visiting your GP to investigate possible medical causes .
DR RHIANNON SNIPE
Dr Rhiannon Snipe is an Accredited Sports Dietitian , lecturer and researcher in Sports Nutrition at Deakin University . She was recently awarded the 2017 Sports Dietitians Australia ‘ Emerging Researcher Award ’. To read more , click here : www . deakin . edu . au / about-deakin / people / rhiannon-snipe
Winter 2018 ReFuel Magazine 15