This might sound weird but due to the cold weather people seem to put less stress on drinking water than they do in the summer months. This is a big mistake, being cooler doesn’t mean you need to hydrate any less then you would normally.
Commonly it is said, that as soon as you are thirsty, you are dehydrated and to operate at your peak levels, you need to be hydrated.
Here are some shocking numbers from Human Kinetics “Exercise performance is impaired when an individual is dehydrated by as little as 2% of body weight. Losses in excess of 5% of body weight can decrease the capacity for work by about 30%”
The article also stated though High Intensity athletes such as sprinters should be just as concerned about hydration as endurance athletes such as marathon runners, as their performances can be just as affected.
Drinking water is a good start but we can all remember famous tennis players eating a banana when they are on their short breaks and it is the potassium that they are after. This article from Web MD talks just about the importance of more than just water.
Staying hydrated helps the blood flow and thus keeps your muscles looser and in better shape. So hydration, just as stretching can make your workout safer and more effective.