I am assuming so as to you already know the worth of water to life. Your body is composed of 60% water. Go lacking it for a a small amount of days and you will notice a difference in your health. Go without it for a few more days and you will be bedridden; do it for a few more days and you won’t need a drop of water ever again.
For a substance that has zero nutritional value, it is the most critical aspect to health and well being. Here we are going to discuss hydration; but more specifically, over-hydration and de-hydration and how you can use water to drink like a world class endurance athlete.
How your body’s water system works
Whether you exercise or not, but even more when you do exercise, you burn glycogen, protein, and fat just by waking up in the morning. The more you exercise, the more you are outside in the heat, or the more you stay in a sauna, the more active your body’s water system becomes and the greater demand it requires to stay within a few degrees of your body’s optimal body temperature parameter of 98.6F (37 C). The most important part of your body’s cooling system is sweat. Think of sweat as a sprinkler system pro your body; it accounts for 75% of all your cooling.
Sweating by itself really does not do your body any good; sweating alone does not cool you down. When you sweat, your body takes the heat that it has generated to keep it within that magical 98.6F and puts it into a liquid form (what we call sweat) and excretes it through your skin. Then it relies on the environment (sun, wind, etc.) to turn that liquid into a gas, which contains your body heat. Therefore, the remaining liquid on your skin is cooler because the heat molecules are gone, making you feel cooler. Super slick stuff right there.
Outside temperatures greatly affect the cooling effectiveness and production of sweat on your body. In hot weather, where there is little difference between your body heat and outside temperature, you are going to need to sweat more to keep your temperature at that magical 98.6F. In cooler weather, you won’t generate as much sweat because the outside temperature generally cools you down. Another factor such as humidity plays a big role in how your body’s cooling system works because the air is already saturated with water and your sweat can’t evaporate; there is really nowhere for it to go. In general, however, I think you get the idea of how sweat, weather and the environment play a role in your body’s water (cooling) system. If not, just know that your body uses sweat and the environment to cool you off. Pretty simple stuff.
On my Audi I have a gauge that tells me when I need more coolant; it also has a gauge for telling me when my brake pads are low and when I need oil. Unfortunately, we don’t have a gauge built into our wrist to tell us that we are dehydrated or a sensor in our nervous system to tell us to drink 4 glasses of water. Usually, I can tell when I’m dehydrated because I get a headache when I’m exercising. Another sign for me is that when I start to feel thirsty, I’m probably already arid and in a zone where I’m not at optimal strength or mental capacity.
Here is a list of symptoms of weight water loss by percentage
1% Thirsty, heat regulation during exercise, performance declines
2% More of 1%
3% More of 2%
4% Exercise Performance cut by 20~30%
5% Headache, irritability, fatigue, spaced out feeling
6% Weakness, severe loss of thermoregulation
7% Collapse likely unless exercise stops
Nutrition for Cyclist, Grandjean & Rudd, Clinics in Sports Med. Vol 12(1);235-236. Jan 1994
So based on this, you know you need to drink water. Now the question is how much do you drink?
What is the standard?
For the sake of argument, we are going to say that one water bottle = one pint, by single water bottle I mean 16oz/473ml. I have water bottles that hold more but were going to use the smaller water bottles as benchmark. So this means that when you see some sports drink that advertises itself as 1 liter, you will know that it means about 2 water bottles full. You will also know that losing 1 pound (~.5kg) means about 1 water bottle in loss. One liter is about 2 pounds (~1kg).
The hole is larger than the spout.
When you are exercising, your body simply cannot replenish the electrolytes and calories at the rate you are burning them. Evaporation from your sweat is much faster than you can drink. Later in this article we will discuss what happened in a study of ultra-marathoners who have tried to over-hydrate only to have hindered performance through a dilution of electrolytes and sodium, but we will discuss this later.
What you are using.
Using averages, you lose about 1 liter (2 water bottles) of fluid per one hour of exercise. When I go on a bike ride on our local and world famous American River Bike Trail, I generally ride between 2~3 hours, so from the time I leave my house to the time I get back, I lose about 3 liters of water; more if it emotional and clammy, less if its cold and dry. I’m in good aerobic shape so I have about 90 minutes of glycogen (sugar) stored in my muscles; if you are in fairly decent shape, you have about the same. If not, you could take about 30 minutes off that. If you are an ultra endurance athlete, you could add about 30 minutes to that time. If you are a Lance Armstrong quality athlete, you could add another 15 minutes to that time.
The endurance exercise outcome is to postpone Tiredness, not replace all the fuel, fluids and electrolytes lost during the event. Dr. Bill Misner- Replacement vs. Replenishment
Under extreme conditions, you can absorb roughly 1 liter (2 water bottles) of water per hour. What I’m talking about here is the extreme maximum. During normal exercise, however, about half of that can be expected.
How much is too much?
Just above I said you cannot drink enough to replace what you are losing when exercising; however, you can drink too much. The reason is that since sweat contains Sodium Salt, you cannot drink Sodium water and have it absorbed into the body at the same rate you are losing it. In a study done with ultra marathoners who tried to drink as much water as possible during a race, it was found that eventually a symptom called hyponatremia (low blood sodium) took effect. This symptom will collapse even an ultra endurance athlete. An even worse situation is a symptom called hypotonic (low blood electrolyte content) when there is not enough sodium or electrolytes, this is the big double whammy. A situation like this will put down even an ultra marathoner.
How to get it right.
Since you don’t have a water gauge for too much or not enough on your body like I do on my Audi, a bit of trial and error is necessary. A general rule of thumb is between 20~25 oz/hr (590~740ml) is sufficient for generally people in good physical condition. So basically, about a water bottle and half per hour of exercise and you should be good to go. If you are a light weight athlete and the weather is colder, then about 1 water bottle should be good. If you are heavier and the weather is hotter, then up the ante. Use your best judgment and listen to your body. don’t write me saying that you took my word as gospel. I’m not there to monitor you; what I’m giving you here is a general guideline.
So get out there, exercise and drink!