Everyone who’s ever been at the gym for all of 10 seconds has heard about the importance of being hydrated while doing sports. You’d be hard-pressed to participate in any sort of group activity and not have someone tell you that you should “drink more water.” This article isn’t here to restate the obvious: You already need that you need to keep your fluid intake up whether you’re pummeling the bag, pumping the iron, or pushing those pedals. Instead, this article is here to demystify the hows of hydration for exercise – specifically:
- How much water you should be drinking by physical activity
- How much water you should be drinking by body-type and gender
- How much water is too much water (Yes, there is such a thing)
How Much Water by Physical Activity
Everyone’s vaguely aware of the need to drink plenty of water each day. Recommendations vary between 13 and 8 cups a day, depending on who you’re asking. Instead of providing a one-size-fits all answer, we’re going to tackle this question from a number of angles. First up, what you’re doing- There’s a world of difference in your hydration requirements by type of physical activity.
Consider this, the primary means of moisture loss during physical activity is sweating. Our bodies sweat to evacuate excess heat produced in our muscles, effectively acting as a refrigerant.
So, common sense – who do you expect needs more water an hour?
A – An Olympic swimmer
B – A Cross country runner in the Nevada desert
The answer is obvious. According to a study conducted by the American College of Sports Medicine, the amount of water needed per hour of physical activity stands as follows:
- Swimming: 0.4 L
- Soccer: 1.5 L
- Tennis: 1.6 L (during a competition)
- Cross-country running: 1.8 L
Keep in mind that these numbers are for a healthy, athletic male. Variation by physiology is up next.
How Much Water by Physiology
A study conducted by the Institute of Medicine published in an extensive 500-page report found that sedentary individuals require much smaller amounts of water than athletes. These results make sense, considering that conditioning the body with intense physical activity packs more heat-generating muscle on your frame, which requires more water to cool down.
The daily adequate intake (AI) levels for sedentary adults were listed as 3.7 liters (130 oz.) for males and 2.7 liters (95 oz.) for females. These numbers amount to 16 cups of water a day for guys and 12 cups of water a day for girls.
The numbers reported for athletes in a counter-study performed by Penn-State Physiology and Kinesiology Professor Larry Kenney are between 3 and 4 liters a day, and in some cases are reported as high as 10 liters a day (for prolonged endurance sports.) A general rule of thumb recommended by Kenney is for athletes to note bodyweight and color of urine. If your urine is dark or your weight is markedly lower, it’s time to drink up.
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How Much Water Is Too Much Water
Dehydration is dangerous, especially when combined with prolonged and strenuous physical activity- Remember that refrigeration example? Not drinking and pushing yourself is like overheating your body’s radiator-literally. Failure to replace fluids adequately can result in impaired heat-dissipation, spiking your core body temperature, the result of which can be permanent damage to your cardiovascular system.
The thing is though, drinking too much water can be just as dangerous as drinking too little- resulting in a condition known as hyponatremia. Hyponatremia results when athletes drink so much water, they dilute sodium and other electrolytes in the blood stream. Electrolyte levels are important- they’re what keep your heart pumping and your brain running. Endurance sports athletes are most at risk.
Symptoms of hyponatremia include nausea, fatigue, vomiting, headaches, confusion, and irritability. If you’re frequently feeling heat-stroke like symptoms while working out and drinking plenty of water, it might actually be that you’re drinking too much. A quick check is to switch to a sports drink (which contains sodium) and see if that fixes the problem.