Never fully understood this stuff until I read this article, which also explains why it may not be a good idea to only drink plain water after exercise in an effort to cut carbohydrates for weight loss – Mike
The importance of post-exercise rehydration
Athletes at all levels often train more than once a day, which means they need to be able to make a rapid recovery between sessions. Most people who take their training seriously are now aware that ingestion of fluids is crucial to maintaining performance and aiding recovery. But the choice of drink can be critical. So which is best, plain water or a specially-formulated sports drink?
To answer that question we need to understand how water is absorbed and used by the body.
The rate at which your body absorbs water depends on a number of factors, one the the most important being the composition of the fluid ingested. It is the concentration of particles such as carbohydrate, sodium and, to a lesser extent, potassium that dictates the rate of absorption in the small intestine. As a rule, the higher the carbohydrate content of a drink the slower the rate of fluid uptake.
* Hypotonic drinks are dilute carbohydrate electrolyte solutions which are less concentrated than body fluids and are therefore rapidly absorbed by the body. They begin the rehydration process while simultaneously helping to replenish carbohydrate energy reserves. No proprietary versions of such drinks are currently available on the UK market since an Umbro product was withdrawn;
* Isotonic drinks have a similar carbohydrate electrolyte concentration to the body’s own fluids. They are best used later in the recovery process to boost energy intake while still encouraging fluid uptake during the final stages of rehydration. Proprietary brands include Liquid Power, Isostar and Lucozade Sport;
* Hypertonic drinks are solutions with a higher carbohydrate electrolyte concentration than body fluids. In general these types of drinks contain large amounts of carbohydrate and are therefore best used as energy supplements during periods of heavy training, when energy expenditure is likely to be high. Again, no proprietary versions are available in the UK, although you can make an isotonic drink hypertonic by making it up in a more concentrated form.
If you prefer to drink water alone after exercise, it is possible to achieve adequate rehydration if solid food which replaces lost electrolytes is consumed at the same time. If this is not possible, some form of electrolyte solution is essential.
This does not mean you should never drink water after exercise – just that you need to take account of your levels of fluid and electrolyte losses. Where losses are high and large volumes of fluid need to be consumed in a short period, it is important to consume sodium in combination with fluids if fluid balance is to be achieved and maintained.
Ian Carlton
This article was taken from the Peak Performance newsletter, the number one source of sports science, training and research. Click here to access these articles as soon as they are released to maximise your performance