The crew at Horleys have seen a lot of changes in sports nutrition in forty-plus years.  One thing that hasn’t changed is the need for anyone who is exercising to pay attention to their fluid intake.  The precise nature of what, when and how much has been the subject of debate since ages ago, and the science of hydration has continued to evolve.  Naturally we’ve been keeping an eye on the research and have tweaked our product formulations and range over the years as result.  So, what’s the latest?

Eight glasses a day. Ah, that old chestnut. Along with ‘drink until your wee is clear’, this is bogus advice. In truth, everyone is different and it comes down to figuring out what you need – which depends on how long and how often you exercise, as well as environmental conditions.  Since hydration status has an impact on, among other things; cognitive function, absorption of nutrients, regulation of core body temperature and fatigue, you need to be aware of fluid intake but there is no need to force it.

Keeping an eye on urine color and frequency is good, although remember that certain vitamins and foods can alter urine color: yes beetroot, I’m looking at you.
You can reference the chart (from the Nutrition Working Group of the International Olympic Committee) as a general guide to your hydration status.  Anything below the neck of the bottle and you ought to focus on increasing your water intake.

The other monitoring tool is your weight, and this is what the pros do. Weigh yourself before and after training sessions – any weight you lose should be replenished and the general rule of thumb is to drink one litre for every kilogram lost.  Alcohol doesn’t count. At all.

It’s a great idea so start exercise in a well-hydrated state but if you are unable to drink much in the morning prior to a workout, make sure you have a full bottle handy so that you can either drink during or at the very least, immediately afterwards.

During exercise, particularly prolonged bouts, it’s essential to avoid forcing fluid intake. The advice to ‘drink before you feel thirsty’ is old school thinking. This is due the potential risk for water intoxication, or onset of exercise-associated hyponatremia, which has serious health implications. Instead, drink fluids as you feel thirsty and in general, no more than 700ml per hour - this will vary depending on individual thirst, sweat rate, and stomach tolerance.

Just as overhydration is a concern, hypohydration (or dehydration) ain’t cool. The science from over 30 years of research still isn’t conclusive but most agree that exercise performance will be compromised once you are more than 2-3% dehydrated.

If you are doing two workouts in a day, it is especially important to pay attention to your hydration so that you adequately rehydrate from the first session and prepare for the following one. Also, if you have a quality workout session planned for the next morning, try to think ahead so that you are not extremely dehydrated the next day.

Less than an hour to 75 minutes of exercise a day – nothing but water. The only exception to this is if you’re experiencing muscle spasms, dizziness, fatigue or cramp: you could be low on electrolytes. To counter this quickly, choose an electrolyte drink such as Horleys Replace, which is optimised for fast absorption.

For exercise lasting over 75 minutes in duration, consider a carbohydrate-containing beverage with no more that 7.5% carbs.  You will need the energy to fuel working muscle, and whilst there is nothing wrong with a low-sugar approach to hydration, fatigue will rain on your parade. The sugars in a properly formulated sports drink – like Replace – are there to help you get the most from every training session.  

Click through to read our more in-depth article on energy. 

Electrolytes are as essential as water and look for a drink that has the Big Four: sodium (most important), potassium, calcium and magnesium.  Sodium is not just there to top-up whatever you’re sweating out.  It enhances fluid and energy absorption from your gut and helps you retain fluid too – both positive effects when you are trying to stay hydrated.

Caffeine in a hydration drink might be helpful for sharpening mental focus and contrary to popular belief it’s not a diuretic so won’t worsen your hydration status. Provided you’re drinking enough to replace what you’re losing, and that solution has a few carbs and electrolytes in it, caffeine is optional.  We say save it for race day (but practice in training).


  • Keep an eye on your urine colour, how often you go, and monitor your body weight.
  • Don’t drink just for the sake of it – too much is as bad as not enough
  • Be prepared, have a bottle of water with you for when you get thirsty
  • Carbs and electrolytes are a must have if you’re exercising for longer than 90 minutes

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