Hydration 101
Hydration 101
Hydration is something that a lot of new runners and triathletes overlook. The longer you exercise the more important hydration becomes. A large number of beginning runners we see don’t know where to start when it comes to hydration. This article will go over the basics of hydration for endurance athletes.
To get started let look at a couple facts that were a result of recent studies from The American College of Sports Medicine Vol. 7;No. 4; July/August 2008 pgs. 202-208 and the Gatorade Sport Science Institute agree that;
• The average runner loses 2-4 pounds of body weight per hour while running a marathon.
• For every two pounds of body weight lost, your heart rate increases 8 beats per minute.
With that in mind, a 180 lb. man running the San Diego Rock & Roll Marathon in 4 hours would lose 8-16 lbs. and a 130 lb. woman would lose 6-10 lbs. of sweat.
As you lose sweat weight, your heart rate increases (8 beats per/minute for every 2 lbs/sweat). The more sweat weight you lose the higher your heart rate goes. The higher your heart rate, the harder your body is working.
Replacing fluids near the same rate lost due to sweating, a runner will minimize cardiovascular disturbance and reduce perceived exertion by not allowing their heart rate to accelerate. By hydrating a runner will not only feel better, but will experience an increase in performance due to their heart rate NOT accelerating.
Next look at what is in a pound of sweat lost. According to Guyton Textbook of Medical Physiology the following amounts of electrolytes are found in 1 pound of sweat.
• Sodium: 400mg
• Potassium: 100mg
• Magnesium: 5mg
• Calcium: 10mg
Replacing fluids AND electrolytes not only minimizes cardiovascular output and increases performance but will prevent cramping due to depletion of the above named minerals.
The question then becomes, how many electrolytes should you replace. The answer is complex and varies based on your weight and the temperature. You should aim to replace 50%-75% of the electrolytes and fluids lost. Here is an example.
Big Jay is going to be running a half marathon. The race day temperature is expected to be 70 degrees and Big Jay is a pretty heavy sweater. He is attempting to replace 75% of his electrolytes lost. In addition, Big Jay weighs 200lbs. Based on this information Big Jay will lose 6.6 fluid ounces per mile. (6.6 fl oz./mile * 13.1 miles)/16 = 5.36 lbs lost from sweat. Based on the information above, in those 5.36 lbs are:
• 2144mg of sodium
• 536mg of potassium
• 26.8mg of magnesium
• 52.6mg of calcium.
As mentioned earlier, Big Jay is a heavy sweater. He is attempting to replace 75% of the lost electrolytes and fluids. So using various nutrition products, he will replace:
• 1608mg of sodium
• 402mg of potassium
• 20.1mg of magnesium
• 39.45mg of calcium
So to conclude, when you are working out it is important to replace the fluids you lose from sweat. Since your sweat consists of water and electrolytes it is important to replace both. The amount of electrolytes you replace is dependant on your weight, the temperature and the distance you are running. The San Diego Running Institute has created a free program to tell you how much you lose on a given run. Stop by and have you free hydration analysis done today!
