The Importance of Hydration

by Justin Norton, International Sailing Academy
Hydration seems like such an obvious concept in our sport. We are outdoors and in constant exposure to the wind and sun. Everyone knows they need to be well hydrated yet few understand when they are optimally hydrated or are starting to become dehydrated. In this article, we will discuss the performance factors of dehydration, how you can stay away from it, and strategies to ensure you are getting what you need.

How does dehydration affect our performance? When we become dehydrated our blood plasma decreases causing thickening of the blood. This leads to the heart and body taking on a larger workload to move the more viscous blood (an increase of heart rate). Losing about 2% of your body weight in fluids (a very small amount) will result in a 4% decrease in performance in both muscular strength and endurance.

In a given day if we are sedentary a 160lb person will lose about 2 liters of water, most of this is through urine and the remainder is sweat in breath. If we are racing in a hot and windy conditions this amount significantly increases. For example if a 180lb person were to forgo fluids on a 4 hour race day they would lose close to 4 lbs of fluid body weight resulting in a 4% performance decrease of their physical output.

With this much water being lost being lost is seems intuitive that our body would constantly be craving fluids. Unfortunately, this is not the case and by the time our body sends a signal to drink, dehydration is well underway. Because we don’t fully retain what we drink in order to replenish fluids it can take between 24- 48 hours to rehydrate if thirst alone is the controlling factor.

So how much should you be drinking on the water? In moderate conditions with heat 750ml/hour is a good number to be hitting. There are many factors that can change this but this is a great place to start. If this isn’t cutting it and you find your weight dropping use that every pound of fluid lost an additional 500ml/pound lost should be consumed.

Of course when we sweat not only water is lost but also waste and nutrients are excreted as well. Most popularly among this list are electrolytes. Adding and electrolyte mix or tablet (such a GU or NUUN) to what you consume on the water is greatly beneficial. If you are on land and in between meals regular water is fine. Pre-made sports drinks? Due to the high glycemic index of most of these beverages, they are not ideal to consume in large quantities and should be left to post-exercise in moderate amounts.

With all of this in mind, how do we gauge our level of hydration?

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