Hydration with Electrolytes

Good hydration is an important skill for cycling. It is easier to become de-hydrated and (less frequently) over-hydrated.


When I started cycling, I had very little knowledge of electrolytes and rarely took any. I rarely cramp, but feel moderate electrolyte use is a much better way of keeping well hydrated. I was partly inspired to write this after recent episode of diarrhoea where electrolyte tablets came in handy. Though it has made me look for some without sweeteners.

Science behind staying hydrated

[Disclaimer: my A grade in GCSE biology and chemistry is well out of date, and of limited weight in such an article. There are potentially more reliable sources on the internet…]

You lose more water when exercising from three sources

  • Water + electrolyte loss from sweating. (You can lose 0.8 to 1.4 litres per hour during exercise)
  • Water used in the creation of energy
  • Water lost from breathing.

With body around 60% water, maintaining hydration is important. Loss of water and electrolytes can hold back performance and even lead to cramping and other problems. Water and drinks manufactures often emphasise studies which show small water loss can lead to big decline in performance.

Whilst there are different opinions about actual extent of performance loss, avoiding excess dehydration is a must for any athlete. It takes quite a bit of preparation and trial and error through practise.

Pure water without any electrolytes

If you are low on water and take on pure water without electrolytes, you can still end up dehydrated.  Cells absorb all the pure water (hypotonic) disturbing the balance of electrolytes in the body and causing a break down of red blood cells. (link)

Also, if you drink just water (hypotonic) it can reduce your thirst because, it will lead to lower salt levels and leave a feeling of bloatedness.

Isotonic Drinks

An isotonic drink will contain a similar ratio of electrolytes and carbohydrate to your blood stream. It will be easily absorbed by osmosis and


The body needs more than water. It also needs key electrolytes to maintain the right balance of cells and.

The main electrolytes are

  • Sodium,
  • Potassium,
  • Calcium,
  • Chloride,
  • Magnesium

Sodium (found in common salt)

  • maintains water balance
  • Levels of sodium influence feelings of thirst
  • Prevents water intoxication
  • Can prevents cramps. Though cramps can be caused by other factors too.

When we sweat, we  lose electrolytes. The main salts lost are sodium and chloride, [electrolytes lost in low concentrations include potassium, magnesium and calcium]. In very heavy sweating, we can even see it crystallise – which is all the salt we are losing. This needs to be replacing or our muscles will start to cramp – giving an indication the body can’t cope with sweat loss.

Colour of urine as test of hydration

The colour of urine is a rough guide to hydration levels. White is a sign of excess water drinking. Dark is a sign of dehydration. The aim is a ‘straw colour’

Although, this is often a rough guide to hydration levels, it is worth bearing in mind it is not without exceptions.

– Some supplements like creatine, beetroot can make urine darker.
– Even light coloured urine can be a sign of dehydration. For example, if the kidney is under-pressure, e.g. cold, the kidney can excrete more water in the urine. Giving a light coloured urine, but you can be under-hydrated.

Lacking in electrolyte. If your body is short of key electrolytes, and you drink pure water, the body can’t absorb the water because it would dilute the electrolyte balance in cells, therefore, the extra water just gets excreted. But, you are still de-hydrated. What you need is water with some electrolyte solution to make it easier to re-hydrate.

Hyponatremia is defined as a decrease in sodium concentration in the blood. This can occur due to sweating and drinking just water without salt replacement.

Examples of dehydration

During hot conditions, it is easy to get dehydrated performing in long events like a 50 mile, but especially 100 mile race. If the temperature increases from 15 degrees to 25 degrees, the change in water consumption can be quite marked. I’ve finished a few 100 miles with mild signs of dehydration, dark coloured urine and a bit of a headache, which requires careful rehydration.

Because of these chastening experiences, I’ve gone to the other extreme and over-hydrated before 100 miles – if it was colder, I’ve ended up having to stop in race to empty excess water.

How to hydrate before a race

It is important not to really over do it. Keeping fairly normal drinking and eating habits is a good rule of thumb.

When hydrating before a race, it is good to have a some amount of electrolytes. This can help the water be absorbed rather than excreted.

I try hard to avoid getting cold or overly hot. For me, the bigger issue is the cold. In middle of summer, I can take a big winter coat so I don’t get cold at 6am waiting for start. This is because, the cold makes my kidneys excrete extra water, which is counter-productive for a four hour race and also prevents proper hydration.

Sources of Electrolytes

  • Table salt is sodium and chloride. (Many exceed RDA)
  • Bananas are a good source of Potassium. Though you can overdose on Potassium; one or two bananas is good limit, if combined with other electrolytes.
  • Greens – magnesium / calcium

However, if riding in the heat, you will need to supplement from usual diet.


  • Coconut water – contains 0.25 litres of coconut water has 46 calories, 9 grams of carbohydrates, 250 mg of sodium, 600 mg of potassium, 60 mg of magnesium, 45 mg of phosphorus
  • Milk – sodium, potassium, calcium and magnesium.
  • San Pellegrino, low sodium, but source of potassium, calcium and magnesium, choloride and bicarbonate. I like taste of this, when cold, though it can have a mild laxative effect.

How much to take

  • It depends on heat, in cold, you can get away without any extra. Though, these days, I will take some, even if it is one bottle with a half a sample.
  • It depends on body type. Some are heavier sweaters. I’m relatively thin and don’t sweat so much.
  • It is important to choose electrolyte with all main electrolytes.
  • I prefer electrolytes without sugar or sweeter so I can add to energy powder or tap water. I got some Science in Sport electrolytes and added them to my Science in Sport energy powder without (electrolytes). It was sucrolose sweetener on top of another sweeter (yuck!)
  • Check energy powder. Some varieties include electrolytes, some don’t. I bought some SIS energy powder, but it has no electrolyte within mix.

Good Electrolyte tablets

It annoys me a little that

  • Electrolyte tablets are so expensive, when there is no good reason.
  • It’s hard to find any without artificial sweetener in. I bought some Torq Electrolyte powder from a local shop, but can’t find it online.


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