It’s getting hot out, and hot inside CFG (Although admittedly not as much as the old place, right?!). We should be concerned with the safety aspects of staying hydrated and most of us are familiar. But there are performance aspects as well that aren’t as well known, but are important to gaining and maintaining fitness.
Your body is 60-70% water. It cools itself by using that fluid to produce sweat. As the sweat evaporates, it carries heat with it, cooling your skin and the blood vessels that are underneath it. That evaporative cooling is why foam coozies work to keep your drink can cool.
We have all experienced the effects of extreme fluid loss in the form of fatigue, headaches, nausea. But even at moderate levels, you experience a drop in capacity that can prevent you from achieving your full potential in a WOD or a competition. The reason is simple: water is a major component of blood plasma. The increased viscosity (thickness of the blood) reduces the output your heart pumps. Less water in your body means lower blood volume for your heart to pump around. Dehydration reduces blood volume, skin blood flow and heat dissipation. This increases your core body temperature and increases glycogen use.
It’s fairly simple to correct though. 
Degradation begins at 1% loss. You’ll experience an increased heart rate for the same exertion due to the reduced stroke volume. Runners refer to that as cardiac drift. While wearing a heart rate monitor, maintaining the same pace, your heart rate will keep climbing at 3-5 BPM for every 1% drop in body mass (On a hot day you wonder why it keeps beeping at you even though you are holding the same pace, or even slowing down).
A 2% drop in body weight results in a 5% drop in VO2 Max heart rate. Your VO2 max is when your body is just holding its own with respect to oxygen use. It’s the maximum you can sustain for about 30 minutes. Five percent is significant- for me it’s about 8-9 beats per minute.
A 2.5% drop in bodyweight due to fluid loss results in a 45% decrease in power output. In CrossFit, we measure intensity via power. Power is where the results are. Operating at a 45% decrement will certainly provide a physical and mental setback to your training.
Some other factors to consider include increased glycogen use, meaning you’ll fatigue faster, lift/run slower, and not be able to lift as much, and also increased lactate production (you’ll get a “burn” quicker).
I had a senior mentor who weighed himself before and after every run. He knew that for every pound he lost he needed to drink a pound of water. To stave off the effects of dehydration, drink 16-20 oz of water 2-3 hours before exercise. This will give your kidneys time to process it and your body time to absorb it. Once you start training, drink 7-10 oz of fluid every 20-30 minutes. Finally, when you are done, replace the fluid pound for pound. It sounds like a lot, but 16 fluid ounces of water equals a pound. Carbs and electrolytes play an important role in maintaining euhydration so don’t be limited to water. When it gets hot, you can use Gatorade or a 50/50 mix.
Too much water is just as much as, or more dangerous, as not enough. If you are a heavy sweat producer, a slow long distance runner, or a heavy beer drinker, then you are at risk for hyponatremia, a very dangerous condition created by diluting your body’s delicate water/electrolyte balance. Pay attention to those post workout weigh-ins. A post-run weight that’s close to or greater than pre-training is an indicator that you are a risk for hyponatremia, especially if all you’ve been rehydrating with is water.
– Coach Jay
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Yes, again, we’ve made it to another Benchmark Friday!!
“Elizabeth”
21-15-9
Power Cleans (135/95)
Ring Dips
