Hydration

On of the blogs I follow decided to do some hot yoga and started into a heat induced episode that involved tingling hands and significant weakness in the hands.  I would classify it as cramping and he was probably getting close to heat exhaustion.  Let him be an example for you, drink your water.  Also, there is a reason for some people to drink sports drinks.  The addition of electrolytes and simple carbohydrates is of benefit for endurance based sports.  The sports drinks are no replacement for water on an ongoing basis, but if you are dehydrated and working in an endurance testing way you cannot ingest water as fast as you can evaporate it out (from sweat and breathing).

Here is a link to an article from Hammer Nutrition on hydration.  Be careful if you are going to push yourself, in a dry environment you can dehydrate in as little as an hour.