11. When you sweat, you lose water from both inside and outside your cells.
The water outside the cells is rich in sodium, an electrolyte that works in balance with potassium. Potassium is an electrolyte inside the cells. Sweat contains about seven times more sodium than potassium, hence sodium is the most important electrolyte to replace during extended exercise.More: Measure Your Sweat Loss for Optimal Hydration
12. Dehydration can hinder athletic performance.
Athletes who lose more than 2 percent of their body weight (3 pounds for a 150-pound athlete) lose both their mental edge and their ability to perform optimally in hot weather. Yet, during cold weather, you are less likely to experience reduced performance, even at 3 percent dehydration.
Three to 5 percent dehydration does not seem to affect muscle strength or performance during short intense bouts of anaerobic exercise, such as weight lifting. But distance runners slow their pace by 2 percent for each percent of body weight lost through dehydration. Sweat loss of more than 10 percent body weight is life threatening.More: How to Avoid Dehydration on Race Day
13. Water can reduce constipation and help with urinary tract infections.
There is also no scientific validation of theories that excessive water intake will improve weight loss, remove toxins, or improve skin tone.
14. You don't need eight glasses of water per day.
No scientific evidence supports the "eight glasses per day" rule, so you can simply drink in response to thirst. You can also monitor the volume of your urine. If your urine is scanty, dark, and smelly, you should drink more. If you have not urinated during your work or school day (8 a.m. to 3 p.m.), you are severely under-hydrated.
15. Bottled water is not always better than tap water.
According to the Center for Science in the Public Interest, nearly half of bottled waters come from municipal water supplies—not from the mountain streams pictured on the labels. This suggests standard municipal tap water is high quality.
Rather than spend money on bottled water, turn on your tap. This will help stop the flood of 95 million plastic water bottles that get discarded each day, of which only 20 percent get recycled. Drink plenty of water—but think "green."More: 6 Reasons Why Water Is So Important
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