Dehydration and Performance - Test yourself !

Very little focus is spent on hydration and many athletes keep making same mistake during training and racing. Check my experience and test and the science behind dehydration.

This weekend I did an interesting (and simple) test calculating my fluid loss during workout and here's what I found out :

Workout #1 - Saturday morning (7:30-11:30am) just over 3 hours aerobic ride followed by 35 min. of aerobic run

Just before I jumped on my bike I weighed myself and right after I finished the workout I weighed my self again:

I lost 10lbs of fluid and I had replenished only 6lbs so net was 4lbs of fluid loss, almost 3% of my total body weight.

Workout #2 - Sunday's morning : (8:00-10:00am) One hour on the trainer with muscle tension work and one hour run.

I lost 7lbs and only had replenished 2lbs so net was 5lbs of fluid loss, 3% of my body weight

Conclusion - Performance compromised, could have felt better (faster with the same effort) specially on the run. We need to pay special attention not to let our fluid loss go over 2% - Drink more and don't forget the electrolytes (salt tablets or drinks)

Now read below about effects of dehydration in performance:

The majority of dehydration problems occur at 2-6% body weight loss. For the typical 150 pound person this means a weight loss of as little as 3 pounds in a single exercise session, which is fairly common. The problems that arise with this kind of weight loss include impaired athletic ability and reduced muscle endurance and strength. However, if more than 6% of your body weight is lost, you are at risk for heat cramps and heat exhaustion. In more severe cases, the athlete could suffer heat stroke or even death. Some signs of heat illness include irritability, headache, weakness, dizziness, cramps, nausea, and decreased performance.

Water is also essential for fat metabolism. The process by which the body burns fat is called beta-oxidation. Water is used during an important step of beta-oxidation and without it, this process could not be completed. It is very important then for those who are trying to lose weight to refrain from dehydrating themselves just so that the number on the scale looks smaller. The weight lost during a single bout of exercise is nearly 100% water, so don't try tricking yourself into thinking that it's all fat loss. You cannot burn fat without water, and fat metabolism will be limited in a dehydrated person.

During exercise, your body gets rid of water via perspiration, as discussed earlier. As your body loses water, the volume of blood plasma in the body decreases, and the heart has to beat faster to keep the blood moving to the working muscles. This causes the stroke volume, or the amount of blood ejected from the heart per beat, to go down. Finally, the overall effect on the heart is that the cardiac output, or amount of blood ejected per unit of time, also decreases. This, in turn, decreases the efficiency of the heart and requires it to work much harder to maintain adequate blood flow to the muscles and vital organs. In a severe circumstance, this could lead to circulatory collapse.

Some people prefer to drink a sports drink to hydrate themselves because they prefer the taste. This is perfectly fine, and some drinks even have salt added to them, which stimulates thirst, making them drink more fluid and thereby staying more hydrated. The addition of salt also helps replace the sodium lost in perspiration. However, a sports drink is not required for most physical activity, although it is recommended for exercise lasting longer than 45 minutes, or of a high intensity. The ideal carbohydrate concentration of the fluid should be 6-8% and certainly less than 7% if the exercise performed requires a high amount of fluid to stay hydrated. Fruit juices, carbohydrate gels, and sports drinks with a carbohydrate content over 8% are not recommended as the sole beverage during exercise. Furthermore, beverages containing caffeine, alcohol, and carbonation should not be used during exercise as they can stimulate urine production, cause gastrointestinal discomfort, or decrease voluntary fluid intake.

Most of us could probably do better at staying hydrated during exercise and even during our daily living. Don't drink only when you're thirsty, as this will not insure adequate hydration. If you struggle with drinking enough water throughout the day, try to drink even when you do not feel thirsty. When you feel hungry, first drink some water, as thirst is often disguised as hunger. Another strategy is to always have water available to drink. Many individuals find that it is easy to drink enough when the water is in front of them. Remember, as you improve your hydration, you will be able to perform better as an athlete and your body will be able to stay healthy and strong. Staying hydrated is about much more than simply satisfying your thirst, it's about enabling your body to be as healthy and fit as possible