Fluid and Electrolytes for Endurance – Kokoda Challenge

fluid and electrolytes

Are you aware of your fluid and electrolytes?

By drinking regularly during exercise, athletes can prevent declines in concentration and skill level, improve perceived exertion, prevent excessive elevations in heart rate and body temperature and improve performance – good justification for every athlete and coach to make fluid replacement a key priority during training and competition.

It is very difficult to replace all fluid lost whilst exercising, due to the volume of sweat, as well as time cost of consuming fluid.  Athletes need to regularly plan and practice fluid intake before, during and after activity.

It is essential that athletes are well hydrated before exercise, especially endurance events. Fluid consumption should be increased for 24 hours preceding training and competition. To be adequately hydrated, the urine should be clear.


Any level of dehydration will decrease sports performance – a 1% loss of body weight generally decreases sports performance by 5%.

Adverse effects of dehydration

There are many adverse effects of dehydration including:

  • Heart rate and body temperature increase. 
  • Perception of work / effort increases.
  • Muscular endurance and aerobic capacity are reduced. 
  • Reduced concentration, mental functioning, and skill learning ability.
  • Cramps, nausea and headaches.
  • Delayed gastric emptying, making it harder to rehydrate. Fluid intake when dehydrated can lead to stomach upsets.
  • Inability to urinate a few hours after an endurance event.

Over-hydration (Hyponatremia)

fluid and electrolytes

Hyponatremia, also called water intoxication, is generally the result of drinking excessive amounts of plain water which causes a low concentration of sodium in the blood. Once a rare occurrence at sporting events, it is becoming more prevalent as participation increases and more novice exercisers are entering endurance events.

Sports Drinks

Sports drinks are viewed as a very important adjunct to an athlete’s training, and for good reasons. Fluid and carbohydrate ingestion have both been found to enhance sports performance, so together they have an even greater effect. Sports drinks replace fluid, carbohydrate, and small amounts of sodium simultaneously.

When purchasing a sports drink the Institute of Medicine recommend the formula to contain the following ratios of sodium to potassium to carbohydrate to ensure maximal uptake and a correct electrolyte balance in the body:

  • 20-30 mEq/L sodium
  • 2-5 mEq/L potassium
  • 5-10% carbohydrate

If your sports drink is low in carbohydrate you will need to look at substituting food in the form of carbohydrate to maximise fluid absorption and gastric emptying.

To work out your rate of sweating weigh yourself prior to training then again at the end. Take note of the quantity of fluid you consumed in your training session. If you drank 1 litre but have lost 1 kg it means that you still have a fluid loss of 1 litre, which is a total fluid loss of 2 litres in the session.

PRACTICE your fluid and electrolyte training prior to your event, you need to make sure the fluids you choose are right for you!

If you are confused about hydration seek the advice of a trained professional and they will help you with work out a hydration plan to suit your needs.

Happy healthy training


BHSc- Nutritional Medicine



Casa D, Clarkson P & Roberts O 2005, American College of Sports Medicine Roundtable on Hydration and Physical Activity – Consensus Statements, Current Sports Medicine Reports, Current Science Incorporated, 4, 115-127, viewed online 7 March 2016 <https://www.acsm.org/docs/publications/Roundtable%20on%20Hydration%20and%20Physical%20Activity.pdf?sfvrsn=0>

Dunford, M and Doyle, 2008, Nutrition for Sport and Exercise, Thomson Wadsworth USA

Hieman D, Fluid, Electrolytes and Dehydration, viewed 7 March 2016 <http://forms.acsm.org/TPC/PDFs/12%20Heiman.pdf>

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