Dehydration is not a joke and places athletes at significant risk of fatigue, poor performance and risk of injury. Our bodies are 50-65 percent water, blood is approximately 92 percent water, brain and muscles are 75 percent water.
Dehydration results in a decreased blood volume which leads to low blood pressure and slower heart rate. It’s impossible to physically perform at optimal level if your blood pressure and heart rate are low.
Dehydrated muscles are twice as likely to be injured as properly hydrated ones. Not a risk worth taking.
Read more at http://www.parkathletics.com/article/1936.php.