top of page
  • Writer's pictureVitxCycle

Staying hydrated - all you need to h2o

We’re looking at hydration in this blog, discussing why it’s important to manage your hydration level, what you should consume to stay hydrated, when you should consume it and if you can consume too much!

If you’re going into a big race or training hard, you’ve probably worked out exactly when you’ll eat to fuel your efforts, but what about what and when you’re going to drink?

During an event a lot of us base our cycling hydration strategies on an ‘as and when’ basis relying on organisers placing their refuel stations at appropriate distances on the route. But when you learn that just 5% dehydration can result in up to a 30% reduction in performance – it’s time to put the same amount of thought into your hydration strategy than you do for your fuelling one. If you don’t put any thought into your fuelling strategy……well that’s another blog!

We’ve brought the following information together to help you know more about staying hydrated for optimal performance, including when to use a rehydration product and when water alone is enough. Yes, you can use just water!!!!

So back to the basics. What is hydration?

Dry mouth, fuzzy brain, that heavy-legged feeling when you’re reaching the end of a long ride, most of us have suffered the signs of mild dehydration, even if we didn’t recognise them at the time.

Fundamentally hydration describes the levels of water held within the body. Every cell, organ and tissue needs water to work efficiently and it makes up more than half of your body weight – around 60% in men and 50-55% in women, owing to the difference in body fat percentage.

Water is vital for keeping us alive and has many functions including regulating body temperature, removing waste products, regulating blood pressure, lubricating and cushioning joints (I know if I’ve not kept my fluid levels topped up my back feels a lot tighter) and it also helps us digest and absorb food more efficiently, increasing energy and delaying the onset of fatigue.

You lose water through – going to the loo, sweating, breathing, you even lose a small amount through your skin – and those lost fluids need to be replaced regularly which we do mainly with the everyday food and drink we consume. Of course, this becomes even more important if you’re exercising or during warmer/hot weather both of which increase the rate of water loss. If you find yourself in that double whammy of exercising in hot weather, under these conditions your body produces more sweat to keep you cool causing more fluids and salts to be lost and therefore increasing the levels of water which needs to be replaced.

What happens when you’re dehydrated?

The British Nutrition Foundation says just 1% dehydration can have negative effects on the body and these increase the more dehydrated you become. According to British Cycling, 4% dehydration will decrease your capacity for muscular work, at 5% you can suffer from heat exhaustion, at 7% you may experience hallucinations and at 10% you’re in serious territory with circulatory collapse, heat stroke and even death. (After writing this, I have literally gone and re-filled my water bottle, I’m not taking any chances!)

The symptoms of mild-to-moderate dehydration include:

  • A dry mouth

  • Headaches

  • Poor concentration.

All of these can cause a loss of form when you’re cycling. When you’re dehydrated your blood volume decreases meaning your heart must work harder, your heart rate, metabolic rate and breathing rate can all increase. You have a decreased sweat rate so your body temperature can increase and you’re also more likely to suffer muscle cramps and injuries, nausea and fatigue due to increased glycogen use. None of which is ideal when you’re training or racing.

How do you know if you’re dehydrated?

Without drawing blood and doing a lab analysis or hooking yourself up to a sweat-test machine, you have to rely on some pretty manual methods for spotting dehydration.

  • Thirst: If you’re dehydrated – you feel thirsty. Thirst comes when you’re already slightly dehydrated so if you’re exercising try and drink before it hits. (*tip - set a 20min reminder on my bike computer to take a drink)

  • The Pee Test: Next time you go to the toilet, check the colour of your urine, it should be a pale straw colour – bright yellow or orange and you need to drink more.

  • The Sweat-Loss Test: Weighing yourself before and after a long session allows you to calculate the amount of fluid you’re losing through sweat. From this weight loss, you can discover how much you should be drinking as you workout, to ensure you stay hydrated.

To calculate your sweat loss:

  1. Weigh yourself in minimal clothing before you workout and again when you finish.

  2. Remember to remove any heavy sodden kit and subtract any fluids you’ve drunk during your workout.

  3. The difference between the two weights is your sweat loss and each 1kg lost is equal to 1 litre of sweat. It might not be possible to replace all of these fluids as you exercise but aim for at least 75%.

How much should I be drinking on a daily basis?

The NHS recommends drinking around 1.2 litres of fluid a day to replace normal water loss but the amount of fluids we need varies from person to person, depending on activity levels, weight, the temperature and various genetic factors. If you’re exercising regularly then you’ll want to increase that volume and also consider including some electrolytes in your fluids.


Electrolytes are salts and minerals found in the blood that conduct electricity when mixed with water. They’re essential for normal bodily functions and, importantly for athletes, help keep you hydrated, regulate nerve and muscle function, regulate your blood pressure and PH level and help rebuild damaged tissue. Sound pretty useful hey!?!

Some of the more common electrolytes and their basic functions in the body include:

  • Sodium – helps conduct nerve impulses and stimulate muscle contractions, supports control blood pressure and volume.

  • Calcium – influences muscle contractions, helps maintain a regular heartbeat.

  • Potassium – contributes to muscle contractions, especially of the heart and digestive system, helps with energy production.

  • Chloride – helps maintain a healthy balance of bodily fluids.

  • Magnesium – supports nerve function, helps with muscle contractions, regulates the use of nutrients for energy, helps maintain a regular heartbeat.

All of the above electrolytes are lost when you sweat!

An imbalance in electrolytes can cause muscle weakness and spasms, fatigue, confusion and dizziness. If you’re exercising intensely or for long periods, to perform at your best you’ll need to replace some of the electrolytes you’re losing and there are plenty of great products out there that you can pick up from your local bike store that will do the job.

Hypotonic, Isotonic or Hypertonic?

When you’re choosing an electrolyte-rich sports drink/additive to your own water bottle you may be wondering what’s the difference between isotonic, hypertonic and hypotonic. Here’s a quick guide to what the labels actually mean:

  • Hypotonic – contains a lower concentration of carbohydrate than blood, hypotonic drinks flow naturally and rapidly into the bloodstream and are most effective at replacing lost fluids at pace.

  • Isotonic – contains the same amount of carbohydrate as blood. Isotonic drinks require more energy to get across the gut wall and so energy and electrolyte release is slower.

  • Hypertonic – contains more carbohydrate than blood. Most sports recovery drinks are hypertonic but if taken during exercise they can cause gastric issues and leave you feeling more thirsty.

How to hydrate optimally for exercise

For training sessions up to 60 minutes

For most shorter, low-to-medium intensity training sessions drinking water should suffice as your electrolyte balance shouldn’t be affected too much.

However, if you’re doing a high-intensity workout such as intervals or hill reps – especially if it’s hot or you sweat excessively – you may benefit from replacing some of those electrolytes. A hypotonic drink would serve you best here.

For training sessions over 60 minutes

When you’re training for more than an hour, it’s important to replace some of the electrolytes and calories you’re losing during that session, to avoid the effects of dehydration and fatigue.

Remember you don’t want to wait till you're thirsty or hit the wall to refuel, pre-fuelling with 500ml of your chosen electrolyte mix one-to-two hours before your session and then aiming to drink two or three good-sized sips every 10 to 15 minutes, will help your energy and hydration stay balanced. A mix of hypotonic and isotonic is best here.

For prolonged training sessions (greater than 2 hours, so basically every ride-out!)

Out on the bike for more than two hours? Then you’ll need to take on more energy and electrolytes than you can get from a rehydration mix alone.

Aim to drink 500ml each hour and complement it with two to three bites of an energy bar (or similar) every 20 to 30 minutes to ensure you have enough fuel to get you over that finish line. Again, a mix of hypotonic and isotonic is best here, with potentially a hypertonic based drink for post ride recovery.

And remember when taking fluid onboard during exercise, regular small sips are better than big gulps as this allows your body time to absorb the liquid and helps prevent air being swallowed and then feeling bloated, which will impact performance.

Can I drink too much?

In short, yes you can. We’ve all heard the horror stories of hyponatraemia – where people drink too much water in endurance events such as the marathon, severely diluting the sodium level in the blood and causing bloating, nausea and in severe cases seizures and death.

Taking on rehydration drinks can help prevent this as you’re replacing sodium and lost electrolytes as you go rather than affecting the balance of your body’s fluids.

How to rehydrate after a workout

After you’ve finished a tough training session you’ll continue to sweat and lose water for a while and it’s important to rehydrate and replace those lost energy stores. This will help your body repair and recover from the stress it’s been under.

Ideally, you should aim to take back onboard 150% of the fluid you lost through sweat within the four hours post exercise – take your time over this as you don’t want to end up feeling bloated and nauseous.

We all know that following exercise it’s important to re-fuel and replace lost calories but if you really can’t face any food post-ride, using a rehydration drinks with carbohydrates will go some way to upping your glycogen levels.

Struggling with hydration and muscle performance?

On long rides cramp, muscle contraction and dehydration can impact performance, and if they become a recurring issue can lead to more serious injuries and issues. Key components of any hydration strategy whilst undertaking prolonged exercise are electrolytes - these substances help conduct electricity and play a key role in orchestrating muscle movement, hydration and maintaining pH levels.

During prolonged exercise these can become unbalanced due to a number of reasons. Interestingly many conflate this with water loss from sweat during exercise – however your muscles actually dehydrate themselves in the recovery period immediately afterwards.

Each electrolyte has a role to play – for example calcium and magnesium are needed for muscle contraction/relaxation and sodium helps maintain hydration via osmosis. When electrolytes become imbalanced it can lead to issues such as muscle weakness or excessive contraction (i.e. cramp).

As an endurance athlete exercising for over two hours, sometimes in warm and hot temperatures. It is worth using an energy drink which contains electrolytes or an electrolyte tablet if you are looking to avoid sugar or sweeteners, for all the reasons given above. Whichever product you choose we hope you now have the information to help match the appropriate drink with the needs of your activity and this helps you stay on top of your hydration strategy.

Happy cycling


Recent Posts

See All
bottom of page