Cold weather hydration: When not to listen to your body

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If you are like most martial artists, you hydrate diligently during warm weather practices and workouts. If anything, the dry feeling in your mouth and your drenched gi or dobok remind you that you need to drink more water.

Winter training can be deceptive in many ways when it comes to proper hydration.  If you train indoors, the dry, heated air can dehydrate you just as rapidly as any day in spring or summer.  The lack of humidity causes your sweat to evaporate more quickly, taking away one of the key reminders that your body needs fluids.

However,  a more insidious deception can occur during the winter months.

When the body sweats during warm weather, blood volume decreases in your body’s core, triggering a chain of events that ultimately leads to thirst.  Thirst is the alarm from the brain that excessive fluids have been lost and need to be replaced.  One of the main tripwires for this alarm is the decrease in blood volume.

Studies at the University of New Hampshire have indicated that cold weather can cause an internal deception that can ultimately lead to a 40% decrease in the thirst sensation.  When exposed to cold weather, the body’s natural reaction is to draw blood from the extremities into the core.  Anyone who exercises outdoors during the winter months will be familiar with the feeling of a warm torso and frozen hands and feet.  This phenomenon is called vasoconstriction and is one of the body’s natural defenses against hypothermia.

Despite the loss of fluid through sweating, the chain of events that culminates in thirst does not even begin, mainly due to the increased blood volume in the body’s core.  During cold weather training, this is how the body inadvertently fools itself into thinking that it is not thirsty, even as fluid is continually being lost. 

What does this mean to you?  This simply means that, despite your body’s need for hydration, you may not feel thirsty enough to take a drink.  Be proactive, and drink at regular intervals based on time and not how you feel.  As always, drink before you go to class or work out – this rule should be followed regardless of the temperature.  This one time, let your brain and the clock make the decisions instead of listening to your body.