How Much of an Effect Does Hydration Have on Practice & Performance?

Everyone seems to be pretty good about staying hydrated nowadays with the popularity of reusable water bottles and a growing number of public water refilling stations in schools, airports, etc.But how much of a difference does hydration make when it comes to practicing and performing more effectively? How exactly might we benefit from being better hydrated? How dehydrated would we need to be to start seeing negative effects? And what would those negative effects even be?There are a number of ...