Dehydration: The Hidden Culprit

If you're a runner, you probably know all too well about training-related injuries. If you've not experience one personally, then you probably know someone who has. Often such injuries are caused by doing too much too soon, over-training, pushing too hard, or coming back from a previous injury too soon. And then there is the occasional injury that just happens for no apparent reason. But, one cause of running related injuries that's often overlooked is simply dehydration...not drinking enough H2O.

When we see a plant wilting, the first thing that comes to mind (even if you have a brown thumb) is, "Gee that plant needs water." But when it comes to a running-related injury we often look for the most complex reasons for why an injury has occurred. Often it's as simple as not drinking enough fluids pre-, during-, and post-run. 

Okay, I'm pretty sure they're are some naysayers out there, but maybe this will change their minds. Research shows that when you dehydrate a muscle by only 3%, a runner can lose about 10% of contractile strength which can cause an 8% loss of speed. A study conducted at Ball State University showed a 7% drop in speed over 10 kilometers by runners who were dehydrated by just 2%-3%. That's only 3-5 lbs for a 165 lb runner.

So what exactly is Dehydration? Dehydration can be defined at a loss of 1% or greater of body weight as a result of fluid loss. The signs of dehydration are varied, but here are a few:

• Fatigue
• Headache
• Heat Intolerance
• Dry Mouth or cough
• Flushed Skin
• Loss of Appetite
• Light-headedness
• Dark opaque urine 

So how does dehydration cause running injuries? Well, the human body strives for balance (homeostasis). Proper fluid levels helps maintain this balance. Proper heart function, blood pressure, blood flow, muscle function, temperature regulation, proper digestion, joint cushioning, energy production all depend on sufficient fluid levels in the body.

Dehydration is often the hidden culprit. You may think your pulled calf muscle is due to that intense hill workout....and that may very well be the main cause, but doing the intense hill workout not properly hydrated is setting yourself up for injury. You're muscles aren't going to perform at 100% when not well hydrated. Also, not properly rehydrating after a hard workout or long run puts you in a hydration deficit going into your next workout.

Your brain doesn't work as well when you're dehydrated either causing changes in mood, irritability, lack of concentration which can all affect your judgement on a run. 

There are going to be some individuals who read this and think, "Well then, I'm going to drink gallons of water each day during training to offset dehydration." Like most things, however, too much of a good thing can be bad. Over hydration can deplete your electrolyte stores (sodium, potassium, calcium, chloride magnesium) which are needed as well for homeostasis. Sodium is needed for proper hydration and potassium is needed to help a muscle relax after contraction. Potassium also is important in regulating blood pressure. So, don't overindulge. There is a formula you can use ( Men: drink daily in ounces your body weight x .35; Women: drink daily in ounces your body weight x .31), but I recommend to just drink water throughout the day. You can have your caffeinated beverages (i.e. your morning coffee), but don't count it as one of your water sources.  

The Sweat Rate Test is a great way to make sure you properly rehydrate after a run. Do this test on a mild day and on a really hot/humid day. This way you'll know about how much water to replace after both types of runs.

Sweat Rate Test:

1. Weigh before running (running clothes on, but shoes off); record the amount
2. Run for 60 minutes
3. Weigh after running (running clothes on, but shoes off); record the amount
4. For each pound lost, drink 16oz of water. (i.e. 3lbs lost = 48oz)

No need to gulp down the replacement water, but make sure you replace that lost water in the hours after your run.

Drinking water is great for most workouts lasting 45-60 minutes. But, if you're running over an hour, be sure to drink a sports drink or use an electrolyte replacement tab in your water to offset the electrolyte loss from perspiration. For runs longer than an hour, sports drinks will also provide fuel (carbohydrate) replacement for your muscles. On long runs, its a great idea to wear a hydration belt, carry a handheld water bottle, or stash some bottles of water and sports drink along your route. FYI: Drink water when taking an energy gel or GU. Drinking sports drink when taking a GU can give you a double-whammy of carbs causing stomach distress.