• Alexa

Hydration for sport

Updated: Jun 2, 2018

Dehydration occurs when amount of water leaving the body is greater than the amount being taken in. Sweating leads to decrease in circulating blood volume leading to thickening of blood, strain on cardio vascular system with rise in heat rate which hinders performance.


If you are dehydrated by as little as 2% your performance will be impaired. If dehydration is 5% aerobic capacity is reduced by 30%. A water loss of 9-12% of an individuals total body weight can result in death.


Symptoms of dehydration usually start with thirst and progress, if you already feel thirsty then you are already dehydrated;

  • mild dehydration (around 2% of fluid loss)

  • thirst

  • loss of appetite

  • dry skin

  • skin flushing

  • dark coloured urine

  • dry mouth and lips

  • fatigue and weakness

  • dizziness

  • 5% fluid loss;

  • increased heart rate

  • increased respiration

  • decreased sweating

  • decreased urination

  • increased body temperature

  • extreme fatigue

  • muscle cramps

  • headaches

  • nausea

  • tingling of the limbs

Tips to stay hydrated;

  • Drink little and often

  • Don’t wait until you are thirsty

  • Aim to meet 1ml of fluid per kcal burnt

  • Aim for straw coloured urine

  • Drink 5-6ml/kg body weight at least 4 hours prior to exercise

  • Calculate fluid loss during training by weighing yourself before and after the session, then divide fluid loss into 10-15 minutes segments and aim to drink that much in next session

  • Replace 150% of fluid loss after exercise

  • For training over an hour some sports drink or energy is recommended. Under an hour and it’s not.

Sports drinks contain fluids, carbs and electrolyte. There are three types;


Isotonic; provide carbs and maintain hydration

  • same osmolality as bodies fluids. 

  • 4-8g/100ml carbs

  • ideal for sports where both hydration and carbs limit performance

Hypotonic; maintain hydration

  • less than 4g carbs per 100ml

  • provide better hydration

  • for enough fuel for long workouts

Hypertonic; provide carbs

  • Higher osmolality than the body

  • slower to absorb

  • higher than 8g per 100ml

  • useful after exercise

  • need to be used with hypotonic drinks during exercise

Homemade sports drink, fruit juice and water;

  • isotonic; 50:50 juice and water plus pinch of salt

  • hypotonic; 750 water to 240 juice plus pinch of salt

The ideal drink should; taste good, not cause stomach discomfort, provide some carbs and electrolytes. 


Look at lots of sports drinks and compare by;

  • carb concentration

  • type of carb used

  • other ingredients like electrolytes, sweeteners, vitamins

  • claims made on label

Electrolytes have a number of roles; muscles contraction, fluid balance, maintaining PH balance. The most common electrolytes are;

  • sodium

  • potassium

  • magnesium

  • chloride

  • calcium

Maintaining an electrolyte balance is important for blood acidity, muscle contraction and other important processes so including them in sports drinks helps keep things in balance, avoid cramp, maintain performance and gives you thirst to drink more.



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Reading, UK & surrounding area

alexa@ontherunhealthandfitness.co.uk

Tel: 07557 852600

Alexa Duckworth-Briggs

BSc LSSMDip MISRM

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