Adequate hydration is essential for getting the most out of your body. Every cell in our body requires water to live and even more water is required when the body is recovering from damage induced through training. So it is very important that you are hydrating properly if you want to maximise the benefits of your training, especially as requirements change in warmer weather which we are now experiencing.
What to drink?
When we sweat we lose water and salts. These salts or electrolytes (sodium, potassium, magnesium, calcium, chloride) cannot be synthesized by the body so when they are lost we must ingest them. Simply drinking water will replace water but not the electrolytes. This can be detrimental as it can dilute the body’s electrolyte concentration, creating a low salt state, or hyponatraemia (low blood sodium). This is a real risk in events such as the marathon with recorded deaths as a direct result of this. A great book by professor Tim Noakes called Waterlogged explores hyponatraemia more deeply if you are interested in learning more. Cool fluid at approximately 15 degrees Celsius has been shown to be absorbed fastest.
Many sports drinks do contain electrolytes. However, these are also usually combined with a high proportion of glucose or sugars at around 60-80g/L – these sugars do not aid rehydration at all. The glucose is beneficial only as an additional fuel that is utilised during exercise – this is only required for intense events lasting greater than 90 minutes up to 2 hours. Further to this, consumption of too much glucose will create stomach upset if the stomach is unable to absorb it all. The sugars can also contribute to dental erosion. A healthy individual should not require any additional glucose during an event shorter than 90 minutes because their body already will have stored sufficient amounts of glucose (as glycogen) in the muscles and liver. For this reason, water and electrolyte drinks are preferred over sweet sports drinks. These can often be hard to find amongst the big brand sugary rehydration drinks however supermarkets and specialty sports stores do often sell them. One well known product is Hydralyte which has a lower glucose content (20g/L). The low glucose contest in Hydralyte may help assist the active transport of sodium and glucose through the small intestine. Alternatively, zero sugar electrolyte products from Shots or High5 are also available.
How much should I consume?
This will vary for everyone based on the following:
- Genetics – some people innately sweat more thanothers
- Body size – larger athletes tend to sweat more than smaller athletes
- Fitness – fitter people sweat earlier in exercise and in larger volumes
- Environment – sweat losses are higher in hot, humid conditions
- Exercise intensity – sweat losses increase as exercise intensity increases
Each kilogram of weight lost is equivalent to approximately one litre of fluid. Adding on the weight of any fluid or food consumed during the exercise session will provide an estimate of total fluid loss for the session. For example, an athlete who finishes an exercise session 1kg lighter and has consumed 1 litre of fluid during the session has a total fluid loss of 2 litres. (Australian Institute of Sport, 2014)
Dr Brendan O’Loughlin is an experienced Osteopath at Melbourne Osteopathy Sports Injury Centre. He is a competitive triathlete and has fantastic experience treating all sorts of sporting injuries.
J. Maughan, R., & Shirreffs, S. M. (1997). Recovery from prolonged exercise: restoration of water and electrolyte balance. Journal of sports sciences, 15(3), 297-303. http://www.ncbi.nlm.nih.gov/pubmed/9232555