Staying hydrated is a crucial function of life, and pre-hydrating and rehydrating before and after exercise is a task that many athletes put a lot of effort into. There are so many “sports drinks” on the market these days, that it is easy to be confused by choice. And whilst we seem to have an abundance of options, do they really do what they are supposed to do?

Why is Hydration so Important?

Water is the most important nutrient that we need to remain alive, and our bodies are made up of approximately 60 to 70% water (around 45 litres of water in a 65kg person).  Water has many critical functions within our body, including regulating our body temperature, producing energy, lubricating our joints, and transporting nutrients and waste products around the body. Whilst we can potentially survive for weeks without food, our life is in serious danger within days without water. In a nutshell, no water very quickly means no life!exercise-hydration-lead2

During exercise (or in hot conditions) sweating is one of the main ways we control our body temperature, along with water also being utilised for energy production. So in sport or warmer conditions (and particularly both together) an athlete can lose a lot of body water.

Consider the following points:

  • Athletes during exercise can lose 1 – 2.5 litres of sweat per hour.
  • Studies suggest if you lose 2.5% of your body weight (under 2L in the above example) from water loss, you will lose 25% of your efficiency.
  • Losing 2% of your body weight through sweating cause a drop in blood volume. This causes the blood to become thicker, meaning the heart must work a lot harder to circulate blood around the body. This in turn can lead to symptoms such as muscle cramps, dizziness, fatigue and in more serious cases conditions such as heat exhaustion and heat stroke.
  • Due to continuing sweat after exercise, and ongoing urinary output, athletes need up to 150% of the amount of fluid they have lost during activity, in order to rehydrate adequately.

Interestingly, cold conditions can end up being as dry as warm conditions, as cold air cannot hold a lot of moisture. So cold air can actually dehydrate us with every breath. Sweat also evaporates quickly in cold dry air meaning further fluid loss. This helps explain why our lips can be prone to chapping in this sort of weather. Add to this the fact we generally don’t feel as thirsty in cold weather, and you can see why cold weather can potentially be as threatening as warm weather.

So now that we see the importance of hydrating, we come to the main point of this article – what is the best way to maintain our hydration levels?

Water vs Sports Drinks

It is obviously well known that we need fluids to maintain our hydration levels. How much fluid we need is another topic in its own right, so in this article we will only talk about what type of fluid:


The most obvious choice for hydration is water – it is cheap, easy, and in abundance. Another advantage of water is also the fact there are no calories or sugar content, so it is very healthy. Water is also easily derived from sources other than bottles, including in foods and from the surrounding air (in the right environment).

One of the issues with water, however, is its blandness and the fact that it can be difficult for people to drink enough water to replace high levels of fluid loss.

Sports Drinks

One main advantage of sports drinks over water is in the taste, which results in people generally drinking larger volumes than they would with water. Another advantage is the fact that sports drinks often contain electrolytes and carbohydrates, which helps replace electrolyte and energy loss during sport. However this advantage must be taken in context: it is unlikely in normal training and many sports events that you will deplete your bodies stores of sodium, potassium and other electrolytes. In many of these mild to moderate duration sports, water is probably the fluid of choice. In sports such as marathons and ironmans, there may be a distinct advantage to replacing these electrolytes and carbohydrates at the same time you are hydrating.

Interestingly, sports drinks are actually absorbed quicker than water. Fluid is absorbed into the gut and the bloodstream quicker when its osmolality (concentration of dissolved particles) is similar to the osmolality of the bloodstream. Sports drinks contain a high degree of dissolved minerals, assisting the speed at which it is absorbed. Many drinks on the market now promote the term “Isotonic” and this basically means that they have the same concentration of carbohydrate as normal body fluid and therefore are easily and quickly absorbed.

The sodium in sports drinks also stimulates thirst which brings up a strange anomaly – whilst you might be hydrating with sports drinks, you may not actually be quenching your thirst! Water does help quench the thirst but may do so before you are adequately hydrated!

Studies have also shown further advantages of the calories in sports drinks, including increasing energy and endurance, limiting the immune system suppression that is often a result of intense training sessions, and promoting faster recovery.

One disadvantage of sports drinks is the risk of weight gain. If you drink sports drinks as part of your every day regime, you may well end up gaining weight as the carbohydrates and nutrients are not a replacement, they are an addition! If you drink these drinks, you need to ensure you are actually burning enough energy to require the replacement. A sobering thought is that some of the popular brands of sports drinks hit you with 9-10 teaspoons of sugar, so if you’re just a recreational sports participant, you probably don’t need (or want) this extra sugar!

Our Summary

It would seem that sports drinks do in fact have a definite place in the hydration process, and are not just a fantastic marketing performance by the producing companies. The most basic formof hydration should involve water, however there are many distinct advantages to sports drinks over water. The main area of concern with sports drinks is to ensure that you require the replenishment they provide, and are not just drinking them as part of your every day diet. You really need to be doing around an hour (or more) of strenuous exercise for the body to deplete enough of its reserves to require the extra carbohydrates that the sports drinks provide.

At the end of the day, the most crucial thing is you are aware of the effects and dangers of dehydration, and implement strategies to avoid this process, no matter what sort of fluid it involves!