Hydration & Training

Hydration & Training

We are all now more aware that it is vital we drink plenty of fluids to stay fully hydrated. But how much do we need? We need to drink enough to replace what is lost- urine, sweat, and even breath. This varies from person to person, depending on age, climate, and physical activity levels. A general recommendation is that we need to drink about 2-3 liters of fluids a day – about half of this normally comes from food and half from drinks.

Ask yourself do you frequently feel thirsty? If the answer is “ YES”- its a clear signal that you’re already dehydrated. And if you continue to go without drinking, the thirsty feeling will shortly be followed by light-headedness, headaches, nausea, and sheer fatigue. A loss of 15-20% of body weight as water will kill you. To avoid this, you need to get into the habit of drinking, try filling a liter bottle/jug with your choice of beverage at the start of the day, keep it close by, drink regularly and it will gradually disappear.

It is not necessary to drink just plain water, like everything else it is down to personal preference and availability.-juice, squash, carbonated beverages, tea, and coffee- exception, being alcohol, where generally the dehydrating effect is greater than the fluid consumed. Also nearly half of your daily fluid intake comes from food – fruit and vegetables are the obvious sources, but there’s also water in things like dairy products, chicken, and bread.

  • It’s unlikely that you will drink too much water- not drinking enough is usually the problem!


Exercise increases our fluid needs. You should start each training session well hydrated. Hydration should be maintained by drinking during exercise, but not so much that you gain weight due to excessive fluid intake. Environmental conditions and how much you sweat will determine your fluid needs- the more you sweat, the more you need to drink to replace the fluid you’ve lost. If you’re exercising at low to moderate intensity for less than an hour then water is fine, but as the duration and intensity of the exercise increase then the need for carbohydrate supplementation is also increased. Sodium intake should also be considered where sweat losses are high-particularly when exercise lasts more than two hours. One of the simplest ways to achieve this is by drinking a sports drink- supplying water, sugars, and salt – to help optimize performance. 

  • Water losses may be up to 1 litre per hour in endurance exercise


Generally, there are two components with scientific evidence to back –up their energy enhancement potential. The one that most of us reach is caffeine. Although, not strictly speaking an energy enhancer, it is a central nervous system stimulant- so can have the desired effect of making us feel awake and perhaps energized.

  • Low doses of caffeine have been found to enhance exercise performance. 

The sensitivity to caffeine varies enormously between individuals, but does not, but does not seem to be related to the habitual amount of caffeine consumed. Caffeine can produce limiting side-effects in some individuals such as insomnia, headaches, and abdominal discomfort, as well as increased blood pressure, muscle tremors, and impaired coordination at high doses- caffeine is also a mild diuretic, but the dehydrating effect is much less than commonly perceived. You have to consume more than 250mg of caffeine- roughly 5 cups of instant coffee, 7 cups of tea, in a short time, for the fluid loss to be greater than the fluid consumed. So it is important to make sure you stay well hydrated, particularly if consuming caffeine in tablet form, or during prolonged endurance training, or when exercising in hot and humid environments.

There are three types of sports drink and their absorption is dependant on their concentration.


  • High concentration containing more carbohydrate

  • Less quickly absorbed

  • Useful if exercising at high intensity for long periods

  • Not the best choice if the fluid replacement is priority


  • Less concentrated than body fluids

  • Designed to be absorbed quickly


  • In balance with body fluids

The other energy booster-its sugars- the essential energy fuel that you will find in any decent sports drink. In essence, sports drinks contain three important components- water, sugars, and salt. Most sports drinks are 4-8%carbohydrate. This makes them “isotonic”- a similar concentration to blood- and, therefore, means that the fluid is quickly absorbed.

So why doesn’t the sports drinks stop there and just contain sugars and water? Well here is a snag- as soon as your mouth is moistened with fluid, your body automatically signals your brain to stop drinking. This inhibition can happen long before your body’s fluid level is completely restored. Therefore, sports drinks also contain sodium chloride- common salt- for several important reasons. Firstly, the salt will encourage you to drink more and so help overcome that automatic inhibition. But also, the sodium helps speed up fluid absorption, aids glucose absorption, and also helps replace electrolyte.

We must drink plenty of fluids. To succeed, you need to plan your drinking strategies and get into a habit of drinking. Make sure you drink enough fluid to replace what you’ve lost. And last but not least, find a drink you like- let’s face it if you don’t like the taste you probably won’t drink enough!

Tomas is a Leeds personal trainer who owns Fitness Designs Personal Training that provides weight loss solutions to the Leeds residents.

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