The 120 mile ride on Saturday got me thinking about hydration. I was pondering on the sad death of the young guy at the London marathon and why/how it happened. It has been reported to be hyponatremia, or to you and me a lack of sodium in the body due to an extreme excess of water being drunk. Any endurance sport, in fact any activity over 90 minutes requires consideration to the nutritional and hydration requirements and this needs to be calculated and practiced during training. There are easy ways to calculate both and for now I’ll just explain in the briefest of terms how to calculate the hydration requirements. Weigh yourself naked before your training session and then go and complete the session taking a note of how much you drink. After the session re-weigh yourself, naked again, and for each kilogram of weight you have lost you need to consume one litre of water. But don’t forget to take in to account any water you have already drunk during the session. If you know that during a two hour session you will lose 2kg of weight then after the session you should consume at least two litres of water and anything up to 3 litres. However, no more is required as this will adequately re-hydrate you. You may also want to consider taking in some of the re-hydration fluid in the form of a sports drink as these contain electrolytes to recharge your lost body stores and are shown to increase the rate of fluid absorption back into the body. So there you have it a simplified hydration/re-hydration strategy. One note to add is that your hydration requirements will differ based on ambient temperature, the type of session you are doing and the amount of clothes you are wearing so the weight test should be carried out a few times in differing conditions.