As well as quenching your thirst, regulating your body’s temperature and avoiding dehydration, water also;

  • Keeps the tissues in your body moist, keeping your body hydrated with optimum levels of moisture for blood, bones, and the brain. Water - also helps protect the spinal cord and acts as a lubricant, cushioning for your joints.
  • Helps your body remove waste.
  • Aids in digestion and is necessary to break down soluble fiber.

Water intake is particularly important when exercising as water is lost through breathing (28%) and sweating (6%).  Exercise can even be impaired by losing 2% or more weight through water loss.    Water weight loss of 6% can cause heat illness, exhaustion, heat stroke and even lead to death.

So how much should you be drinking when training and generally during the day?

In terms of general water intake throughout the day, the NHS still recommends about 6-8 glasses per day – see here> – although it probably also makes sense to use some common sense.  For example, if it’s the middle of winter and your peeing every half an hour maybe your drinking too much.  If it’s summer or your hot and sweaty for whatever reason, you might need to drink more.   Use 6-8 glasses as a guide, but don’t forget to learn to listen to your body, as it’s likely to tell you what you need if you pay close attention.  Things to watch out for:

  • Do you feel dry?  e.g. is your mouth parched?
  • Are you getting cramps in your muscles?
  • Is your pee a dark yellow?
  • Do you feel tired?

In terms of water for exercise, here are the research recommended guidelines:


  • 500ml around 2 hours before exercise
  • 125-250ml just prior to exercise
  • During Exercise
  • On average 1 liter of fluid for every 1000 kilocalories burned or higher in very intense exercise or excessive heat.  This equates to about 250ml every 15 minutes of vigorous exercise-

Research suggests you should replace 1.5x (150%) of the fluid lost during exercise.  1 liter of fluid is equivalent to 1kg of bodyweight, so if you lost 1kg of water weight during exercise, you would effectively drink 1.5 litres to replace it.

Again, with all of this you may need to use some common sense.  These are guidelines and conditions can vary, so trust your thirst.  For example, if you are peeing multiple times before, during and after a workout, perhaps you are drinking too much water!

In my 30s I went through a period where I was getting frequent muscle cramps despite drinking plenty of water.  So I  added a bit more salt into my diet.  I also started taking a more general multi-vitamin (with water soluble vitamins).  This resolved it and I’ve not had the issue since.
- The Lean Exec -

These days salt is demonized as it’s easy to ingest too much with all the processed foods around.  However, it’s worth noting that sodium is an important nutrient for the body and helps with water retention.  So if you generally eat clean (limited processed food) and you have no medical issues linked to salt, don’t be afraid to have some salt with your food, just keep it sensible.  A pinch of salt in water before exercise can also help with fluid retention.


Mayo Clinic
University of Michigan