I’m pretty sure every athlete can tell you how many glasses of water you should have in a day! If you don’t know then look it up…QUICK! The age-old adage of 6-8 glasses of water a day comes from the estimate of how much “fluid” one needs to replace how much is lost from daily activities. I put fluid in quotes because we can also get water from a variety of sources including food, other liquids and the rest from our own metabolism. Vegetables and fruits are the most hydrating (e.g., lettuce is 95 percent water) but we also get a lot from meat, as well as soup, juice, milk and even coffee. (Go Paleo!)
What is Dehydration?
Up to 60% of the human body is water,thebrain is composed of 70% water (brain is like a sponge.. get it!), and the lungs are nearly 90% water. Most of the water is found within the cells of the body (intracellular space) and the rest is found in the extracellular space which consists of blood vessels and spaces between the cells.
Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. There are different forms of dehydration but I won’t get into them all here. What you do need to know is that we lose water on a daily basis when we breathe and humidified air leaves the body (not so much in So Cal but in colder regions), sweat, urinate and have bowel movements. (especially with cases of vomiting and diarrhea.. yes I went there..)
As athletes the sweat factor is one that we are all aware of but what you may not know is that you also need to pay attention to fluid loss through diet, ie Paleo. Any diet low in carbohydrates and high in protein will lead to fluid loss through increased urination. Now this isn’t always a bad thing considering most of the water retention is excess due to glycogen stores from “bad” carbohydrates. (this is what leads to that swole feeling that us women love so much) However this can lead to fatigue, headaches and muscle weakness if you don’t replenish the fluid that is being lost during this time until you body gets used to the diet change.
During high-intensity exercise, a person can lose up to 2.0 liters of water per hour! However, 1.0 liter of water per hour is more common.
Infants, children, elderly adults, endurance athletes and those with chronic illnesses are those who are at a greater risk for dehydration. Besides heat and humidity, which are obvious risk factors for dehydration, living, working and exercising at high altitudes also put you at risk. This is due to increase urination and rapid breathing which is the body’s way of trying to adjust to the higher elevation.
Signs of Dehydration
- Dry, sticky mouth, fatigue, thirst, decreased urination, unable to produce tears, dry skin, sunken eyes, headache, constipation, dizziness or lightheadedness, rapid heart rate, etc. etc.
In medicine a good indicator of dehydration is the color of the urine: Clear or light-colored urine means you’re well hydrated, whereas a dark yellow or amber color means that your kidneys are working too hard to concentrate the urine meaning which is also one of the tell-tale sign of Rhabodomyolysis.(dun dun dun) Another trick I share with my patients is to pinch the skin on their arm and let it go… hydrated skin will spring back to normal right away, any tenting means you need to bee line to the drinking fountain asap! Our bodies have a good way of letting us know what is up… so listen to them!!
Before you roll your eyes just remember that a person can only live around 5-7 days without water before death ensues and that number decreases as the outdoor temperature increases!
The obvious answer is to make sure to drink plenty of water/liquids throughout the day as well as eat fruits and veggies that have high water content.
Rule of thumb:
- Two hours before exercise, 16 ounces (2 cups) of fluid should be ingested to promote hydration and allow time for excretion of excess water.
- Drink 8-10 fl oz every 10-15 min during exercise.
- If you know you are going to do a hard workout or if you just finished getting your ass kicked then make sure you go home and drink at least 20-24 oz.
- If exercising longer than 90 minutes, drink 8-10 fl oz of a sports drink (with no more than 8 percent carbohydrate) every 15 – 30 minutes.
So what is the deal with those sports drinks, gels and bars…
All of the above usually contain electrolytes as well as carbohydrates. The need for carbohydrate and electrolytes replacement during exercise depends on exercise intensity, duration, weather and individual differences in sweat rates. Sodium and potassium are the two of the important electrolytes that need to be replaced after exercise and carbohydrates are what provide energy during exercise over 60-90 minutes. The gels may make you gag but I seriously don’t think I would have been able to do my half marathons without them… I am a believer.
For all of you crazies who do two workouts a day, you are at an even greater risk of dehydration. If you are fluid deficient from the first workout this will carry over into the second workout and your performance go down the drain. This holds true for all of the sweaters out there. (Heavy sweaters put your hands up!!) At this stage most experts would recommend weighing yourself before and after a workout to monitor your fluid loss. (Fun fun fun!!) Anything greater than 2% of your body weight indicates dehydration. (i.e. 3 lbs. for a 150 lb. athlete) At this stage it is recommended to drink 20-24 oz of water for every 1lb lost.
And in conclusion…