Sports Hydration & Fluid Replacement

As simple as it sounds, good sports hydration is crucial to optimal sports performance and water is one of the most important constituent of your diet; you can survive for only a few days without water, although you can live for weeks without food! This is because water constitutes about 60% of our total body weight. This blog will cover some of the basics of sports hydration and remember whilst most people make an extra effort to drink more when exercising during the summer, it is just as important to stay well hydrated when training in the winter.

Believe it or not, but many people are in a constant state of inadequate hydration, though this does not stop you from functioning at home, at work or in sport. However drinking too little water, or losing too much through profuse sweating inhibits your ability to function optimally. The risk of dehydration is further enhanced when exercising, thus fluid should be consumed before, during and after sport so you may exercise at your maximum potential.

To maintain properly hydrated, water intake must equal water output. Water intake varies widely from person to person, and is strongly influenced by habit, but it is typically about 2500ml a day in adults. Water loss occurs in a number of ways; though urine and faeces, evaporation from the skin and expired breath.


We all need to take in around 2 – 2.5 litres (or about 6-8 glasses) of water a day, and not just endless tea and coffee, which are diuretics and will actually dehydrate you further.

The main functions of water are:

  • Provide a medium for the diffusion of gases, as well as transport nutrients and waste products
  • It lubricates joints and cushions organs and tissues
  • Stabilise heat fluctuations

It’s well established that dehydration can have detrimental effects on sports performance. For example during endurance events such as the 10Km run, 1% bodyweight loss through dehydration could result in a 2-5% decrease in pace. This may not sound much, but for the 30-35 minute PB athlete, this would reduce performance by around 30-40 seconds! While a >5% loss can be lethal!

Sports hydration chart

Performance is impaired due to the reduction in blood volume that accompanies dehydration. During exercise, a good blood flow to the working muscles is needed to provide oxygen and nutrients, and, in addition especially if it is warm or humid, a good blood flow to the skin is required for cooling. However, as blood volume drops due to loss of water from sweating, heart rate rises to maintain blood flow to the muscles. This means the athlete has reduced economy and generally less tolerance to exercise. At the same time blood flow to the skin is reduced, as it’s more important to maintain blood circulatory blood volume. Thus cooling is impaired and body temperature rises.

Therefore in winter when exercising outside, the cold can mask the effects of sweating, overheating and a decreased thirst, resulting in dehydration and decreased performance.


  • Are sports drinks more beneficial than water?

Water is an excellent fluid replacement for most recreational athletes who exercise for less than an hour at a time. Water is inexpensive, readily available, and is what your body needs. If you participate in high-intensity endurance events, carbohydrate (CHO) drinks are a superior fluid as help maintain blood glucose concentrations. This will help preserve muscle glycogen and thus improve endurance performance. As with anything, caution must be taken, CHO drinks of a greater concentration than 10% will impair gastric emptying and performance, an optimal level is 7%. However always be aware of high sugar levels in some of the more “commercial” sports drinks; as a rough guide if you can buy it in a garage/corner shop/off license then it’s highly unlikely to be a specialist sports product.

  • When should I drink?

Drinking 2-3 glasses of water in the hour before exercise will help towards ensuring you have the optimal hydration. If you exercise for more than 30 minutes or the intensity of the exercise is extreme, remember to drink regularly during your workout. It is best to sip lightly and regularly rather than gulp. For obvious reasons, the more movement your body has to make, the more uncomfortable it will be if you drink too much. Drinking water to re-hydrate after you finish is of course to be encouraged – ideally NOT alcohol. Also coaches talk of the ‘golden hour’ after exercising, when your muscles will more easily absorb nutrients. Ideally you should eat (e.g. energy bar/banana) and drink (diluted 5% CHO drink) in this hour. It is particularly important to hydrate last thing at night to prepare for the significant loss of water during sleeping and rehydrate first thing in the morning as this is a time when the blood is most viscous and strokes particularly prevalent.

  • How do I know if I’m consuming enough fluids?

A simple way to monitor and maintain good hydration levels is by checking the colour and clarity of your urine. A clear colour indicates you are hydrated, whereas a yellow / dark colour shows you are not (N.B vitamin tablets and some natural substances such as beetroot can darken urine, so check volume as well). This is actually more accurate than just going by your thirst.

  • Is it enough to drink when I’m thirsty?

Though thirst is the driving force for water intake, the mechanism is poorly understood. However by the time you are thirsty, you are already well dehydrated! Furthermore thirst is quenched almost as soon as you begin drinking water, even though the water has yet to be absorbed by the blood. This means that most people don’t drink as much as they actually need, and are in fact most often dehydrated, even if they don’t feel it.

#1 Tip: Water should be drunk little but often throughout the day such that we are never thirsty……leave a bottle on your desk as a reminder to sip regularly.

To see our full range of Sports Hydration and Sports Nutrition products click here.



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Ben Goodridge - MSc, BSc (Hons), Dip ST, VTCT. Ben has over 20 years experience working within the sports industry, in both private and public sectors and from amateur to elite level. After leaving college he worked as an instructor in a private gym and left five years later as Fitness Manager. He then attended university graduating with 1st class (Hons) in Sports Therapy, and was awarded a four month internship at Virginia Commonwealth University (USA) in their sports medicine complex. Upon returning to the UK he combined his time, working at Alexandra Sports, Southampton Football Club, Hampshire Cricket and England Cricket. He then accepted a place at Trinity College Dublin on their highly accredited MSc Sports Medicine course. Following this he worked for the NHS and a private clinic, whilst also lecturing at Chichester University. In 2008 Ben moved away from full-time Sports Therapy, and joined the fire service. He is now a whole-time frontline firefighter as well as a PT instructor, and maintains a strong interest in all aspects of sport, health and wellbeing. His main areas of specialization are strength and conditioning, fitness training and sports therapy / rehabilitation. He enjoys participating in all sports including weight training, rowing, triathlons, football and badminton. He says his biggest achievement was completing the 1994 London Marathon, and most rewarding completing it again in 1999 with six gym members whom he had trained. Whilst studying for his MSc he joined the boat club and made the crew for Trinity College in their annual ‘Colours’ boat race against UCD. In 2012 he organized and completed a big charity challenge, where he swam across the Solent to the Isle of Wight, cycled 70miles around and then kayaked back.