Fluid Consumption during Ultra-Endurance.

Our man at Lucozade, Matt Furber, wants you all to heed his expertise:

Time for my 3rd blog...doesn't time fly!

During exercise, heat production is 15-20 times greater than at rest. An increase in core temperature of 0.2 – 0.3 degrees can result in a significant decrease in exercise performance. Therefore your body needs an efficient way to dissipate the heat production from the core to the periphery so that the body can stay cool. 98% of heat produced during exercise is lost through sweat, therefore maintaining optimal hydration is of utmost importance.

Just 2 % body dehydration (1.4kg for a 70kg male) results in a significant decrease in endurance performance, 4% can result in muscular fatigue, 8% delusion, and 10% or greater can result in death. Don't worry though, this will not happen to you! Therefore starting exercise fully hydrated is essential, the best and easiest way to check that you are fully hydrated is by urine color, the clearer it is, the more hydrated you are - see urine chart below.

However, within 45 minutes of running if no fluid is consumed you can lose 2% body fluid. Therefore, it is essential to consume fluid during the run right from to work go. We would recommend consuming 100-150ml every 10-15 minutes, so about 600-800ml per hour. But, once again, every one is different, with you all having different numbers of sweat glands and sweat rates.

The best way to work your own individual sweat rate is to do a pre- and post-run weigh-in. Weigh yourself with as minimal clothing as possible before your run, then run and take note of how much fluid you consumed, then weigh yourself after. If you weighed 70kg pre-run, went for a 60 minute run and weighed 69kg post and drank 400ml of fluid during, that equates to a 1.4 litre (1kg = 1litre) loss of fluid. So your sweat rate would be 1.4 litres per hour. There is no chance that you would be able to replace all of this fluid as it would require almost constant drinking, however, the more you replace the better.

A way of retaining a higher percentage of the fluid consumed is to combine the fluid with electrolytes (salts). Electrolytes are lost through sweat and if not replaced can result in fatigue and heat illness such as hyponutremia (extreme low salt levels) which can be life threatening. As you will be sweating a lot it is of upmost importance that you replace these electrolytes. All sports drinks have them in and not only do they help with water retention but they are also essential for fluid absorption, brain function, muscle contraction and maintaining fluid balance.

So, the best strategy for you to use would be to combine water with a fluid that has high concentrations of electrolytes (such as Lucozade Sport - funny that!!), and drink little and often.

In summary from the last 2 posts, try and work out a strategy that entails you to consume 600-800ml of fluid per hour (some of which, but not all, that contain a high amount of electrolytes), and also work out how you can take onboard 40-60 g of carbohydrate per hour as well. Drip feeding is best for both strategy, so LITTLE and OFTEN is the golden rule.

Next week….the importance of recovery!

Regards, Matt