Dehydration. It's a devil that's attacked me during training and racing. But it didn't have to. It's almost completely preventable.
Now that summer is with us, we're cycling in the heat much more often. That means you'll be sweating out there on your bike. Here's a quick explanation of what's going on.
Sweat - Your Body's Natural Coolant
Sweat plays a key role in your temperature regulation. Hard working muscles generate heat that your blood carries away to the surface of your skin. The sweat evaporating on the surface of your skin cools the blood flowing just beneath it. Your heart then circulates this cooled blood back to your muscles and core, where it helps regulate your internal temperature.
Sweat, though, is a loss of the stored water within your blood volume. About 70% of your blood volume is water. A loss of this water compromises the overall functioning of your blood supply for athletic endeavors. Your blood gets a little thicker. It begins to lose its abilities to deliver oxygen, glucose and fatty acids to those very same muscles it's trying to cool. Your blood's ability to remove carbon dioxide and lactic acid from those hard working muscles is also diminished. If you don't rehydrate properly, you'll be fighting a losing battle, and your power output will start drooping faster than a popsicle left out in the sun.
So What Is Proper Rehydration?
It's rather easy to determine your own water needs for training and racing. Start with drinking a standard 500ml water bottle - that's the typical smaller sized water bottle that cyclists use - per hour of training. Weigh yourself naked before your next training ride on a warm day. After riding, weigh yourself naked again. The difference in kilos (to convert pounds to kilos simply divide by 2.2) is how much more water in litres you need to be drinking. Take those total litres, divide by the time you were exercising, and you have a good idea how much more than a 500ml bottle per hour will be good enough for your own sweat rates. One of my teammates, Dan W., drinks up to 3 such water bottles per hour.
If the day is hotter than when you did the above test, plan on drinking more. When you're racing, also plan on drinking more because you'll be working harder than a typical training ride. If it's cooler, you can get away with a little less, but in my opinion more is usually better, especially if you're drinking an electrolyte beverage instead of simple water. Overhydration with plain water can disrupt your sodium levels (i.e., dilute them), which can lead to heart issues and death in extreme cases. I've yet to hear of overhydration cases, though, where the athletes were drinking an electrolyte beverage.
Here's a Couple of Strategies to Ensure You Actually Drink Enough
Never take your water bottles for a ride. Those bottles have a purpose, and at the end of a training ride or race they should be nearly empty. If they're still quite full, then you're not only going to suffer a power brownout from your dehydration, but you've also just carried around some dead weight that surely dragged down your overall power-to-weight ratio.
When you're in the chaos of racing, you may forget to drink as frequently as you should. I've got a couple of strategies that usually keep me on track.
First, and this may be easiest for those just starting to race or if the racing takes a lot of concentration, use a countdown-repeat timer on your watch. Set it for a 10 to 15 minute interval. Every time it goes off, drink a good mouthful or two - whatever amount will help you hit your total water bottles per hour estimate.
Second, use a "Monkey-see Monkey-do" approach. Whenever you see someone else in the group take a drink, you take one too. Don't worry if you just had a drink a couple of minutes ago - do it anyway. Look at your bottle levels every 30 minutes and make adjustments to hit your all important water bottles per hour estimate.
Keep on top of your hydration levels and you'll stay on top of the results board.
Photo "Water Bottles" by: LeeBrimelow
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