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Nutrition
Rehydration
By: Michele Ferrari
Published: 17 Jun 2003

The heat is one of the biggest enemies of a cyclist... read about some more rehydration insights.

Summer is coming, and with its heat, problems linked to hydration occur more frequently.

With temperatures over 30°C, a rider can lose as much as a litre of fluid an hour through sweating and respiration, especially on climbs.

Since the quantity of liquid absorbed in the stomach and intestines can be inferior to fluid loss, a hard training program or a race can easily bring about a state of hypohydration.

Be sure to check body weight after training and compare it to pre-training morning weight taken before breakfast. Weight loss above 1% of body weight can indicate hypohydration.

Remember that full fluid replenishment can take between 4 and 24 hours—a rather long period during which the athlete can continue to lose liquids through urination, especially if only water is taken as a replenishment.

Addition of sodium (50-100 mM/l or 3-6 g/l) to water can inhibit the diuretic effect and facilitate fluid retention.

Loss of sodium through persperation amounts to about 1.2 - 5g/l. If one loses 2 liters of sweat (approx. 2 kg of body weight), from 2.5 to 10 grams of sodium will also be lost, depending if you are acclimatized to heat or not; the acclimatization usually requires 1 to 2 weeks and allows you to expel a less sodium-loaded sweat.

It is therefore necessary to reintegrate about 150% of body weight lost during the 12 hours following activity by taking an appropriate quantity of water with:

- 3-5 g/l of salt (NaCl)
- 2% glucose (to facilitate absorbtion)

If you lost 2kg during the training or racing period, you should take in about 3 litres of extra fluids in the 24 hours following the effort.


Caffeine and alcohol are firmly discouraged, due to their diuretic effects.

Remember also that when you are dehydrated by 3%-4% of body weight, gastric functions (and thus fluid absorption and retention) are compromised.

Rehydration is therefore essential also in order to allow the athlete to have a proper food intake.

More from Nutrition :
Training and Racing Food 1 Mar 2003
Some weight loss advice 10 Mar 2003
Nutrition - General Notice 6 Mar 2003
Hydration 18 Mar 2003
Supplements to enhance diet 26 Mar 2003
Rehydration 17 Jun 2003
OverFeeding 24 Nov 2003
Bonking on the Bike 10 Jan 2004
Fat Metabolism and Endurance 31 Jan 2004
How many Carbs? 23 Apr 2006
Caloric Expenditure on the Bike 14 Jul 2011
More on Nutritional Supplementation for Athletes 26 Nov 2011


 
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