Everything You Need To Know About Hydration

It’s summertime. It’s sunny. It’s hot. It’s humid. None of this is a news flash, but how your body reacts while exercising in these conditions may surprise you.
I download triathlon and running related podcasts from iTunes all the time. I listen to these while on my indoor trainer or driving in the car. I recently came across one that featured an interview with Brendon McDermott. Brendon has a PhD in Exercise Science with a research focus on thermal physiology, hydration, and exertional heat stroke. So needless to say, this dude knows what he’s talking about when it comes to hydration! The interview was conducted by Jay Martin, who runs a website called “Triathlon Mind Training”, where he also sells a DVD by the same name.
Staying hydrated is very key to any athlete this time of year, but especially those that have endurance events (such as IMLOU) planned that take place in the heat!  The information that I learned listening to this interview seemed important enough to share with my fellow athletes…so here goes.
First of all, let’s define dehydration. It’s the excessive loss of bodily fluids. For most people, they think that this just means sweat. While it’s true that the majority of fluid loss comes from sweat when we are exercising, we can also lose fluids through urine and respiration. That’s right, every time you exhale, you are losing fluids. This fluid loss through breathing can actually become pretty substantial during endurance events.
So the first step that many people take is trying to determine how much bodily fluids they lose during exercise. The simple way to do this is to weigh yourself naked before a long ride or run, keep track of all fluids that you take in, then weigh yourself naked again when you are done, adding a pound for every 16 ounces of fluid you consumed during the workout. It’s important to weigh yourself naked because your clothes will hold sweat. Just don’t use the scale that’s out in the middle of the gym! One pound of weight loss equals 16 ounces of water loss. For example, let’s say you weigh 1 pound less after a one hour run and you drank 16 ounces during the run. You lost a total of 32 ounces (16 x 2). So you should try and drink 8 ounces of water every 15 minutes while running.
Since this fluid loss rate is very individualized, don’t assume that you are the same as someone else your same size and age. It also varies depending on exercise intensity, fitness level, environment, heat acclimatization and how much sodium you have in your body at the time. So do this fluid loss test several times and get an average.
I’m sure that we’ve all exercised in a state of dehydration. It’s nearly impossible not to. Most people cannot physically take in the same about of fluids that they are losing per hour. But trying to stay as hydrated as possible is important. Even just a 2% loss in body weight due to dehydration can have some very negative effects on your performance and your brain. To find what your baseline body weight is, weigh yourself naked (yes, there’s lots of nudity in this post) first thing in the morning. As with the fluid loss calculation, do this weigh-in several days in a row and take the average. Once you get this weight, multiply it by 0.98 to get your weight at 2% dehydration. The goal should be to not weigh any less than this after your workouts. Also note that your body’s thirst mechanism kicks in when you get to 2% dehydrated. So don’t let yourself get thirsty!
I’ll use myself as an example. Although my weight fluctuates depending on what period of my training I’m in, I usually check in around 175.
175 x 0.98 = 171.5
This means that I shouldn’t weigh any less than 171.5 after my runs or rides.
So what exactly happens when you are more than 2% dehydrated? Bad things man, bad things. According to a study done last year by the Journal of Athletic Training, runners who started a 12K race dehydrated on an 80° F day, finished about two and half minutes slower compared to when they ran it hydrated. Why does this happen? Research shows that for every percent of dehydration (body weight) you are down, there is a direct correlation to increase in your core body temperature. During exercise, what is compromised to keep the body temperature down? Performance. Measuring your body temperature after a workout or race doesn’t tell you much. You may finish the race with a lower body temperature, but your performance suffered.
Exercising in a dehydrated state also causes your mind to play tricks on you. As if endurance events weren’t mentally taxing enough, before you even get to the magic 2% number, your cognitive reasoning decreases. As you continue to lose hydration, reasoning decreases even more. So your judgment, perception, awareness and intuition all suffer. Ever tried to figure out what your finish time will be based on your current pace? Ever tried to estimate how much energy you have left? Ever tried to figure out what mile your are on based on landmarks? All of these things become more difficult when you are dehydrated.
So other than drinking water while exercising, what else can be done to slow down dehydration?

  • Take in electrolytes. I use a product called Athlytes by Millennium Sports. They are little capsules that contain a full spectrum of electrolytes without the sugar and artificial junk found in sports drinks (which my stomach doesn’t do well with). If you don’t like taking pills, try dissolving some electrolyte tablets in your water. Both Hammer Nutrition and NUUN make good products.
  • Carb load before an endurance event. I’ve followed a carb-loading protocol in the week leading up to my last two half-Ironman races and I’ve never once felt thristy or extremely dehydrated during the race. Carb-loading alone will not keep you hydrated, but it can help you retain water. You may feel bloated standing on the start line, but your body will use this fluid retention during the race.
  • Monitor hydration in the 2-3 days prior to your event. Try and consume between 70 and 90 ounces of water daily prior to your event. Your urine should be almost clear. However, if you find yourself heading to the bathroom more than once every two hours or so, you should cut the water consumption back – you are well hydrated.
One last thing that was mentioned was what to do after a long workout or race. Multiple studies have shown that ingesting oral fluids after a race rather than an IV is better for you. While this method obviously takes longer, you will recover more quickly. So don’t go straight to the IV after your marahon or Ironman race. Try and slowly drink some fluids first. If you can’t keep them down, then try and find a vein!
Dehydration is a big concern for me heading into Ironman Louisville next month. There’s a reason why this race has the highest dropout rate of any Ironman on the planet…it’s hot and humid here…people do not keep up with their hydration and they reach a point where their body can no longer move. They go into survival mode. When your body is starting to shut down from extreme dehydration, running walking is not an option! I learned a lot from listening to this podcast that I plan on using on race day, I hope that some of this information is beneficial to you, whether you are doing IMLOU or not.

7/6/11: Swim – Train Smart workout – solo (3400yd on 1:05:03)  
7/8/11: Brick – Bike (9.46 miles in 28:53), Run (1.92 miles in 13:45) 
7/9/11: Race – Cardinal Triathlon (70.3 miles in 5:50:22) 
7/11/11: Bike – Recovery Spin (18.0 miles in 1:00:00) 
7/11/11: Weights – Extreme Core II – 4 sets
7/12/11 Run – Speed Work at track (10.42 miles in 1:42:46)
7/13/11 Run – Recovery Run (3.82 miles in 33:00)  
7/13/11: Swim – Train Smart Group Swim (2450m in 55:23) 
7/14/11 Run – Long Run* (Planned for 16 miles, only ran 6.52 miles in 56:44 due to IT Band issue) 
7/15/11: Bike – Intervals (14.50 miles in 45:01) 
7/15/11: Swim – 100-75-25 intervals (1400yd in 29:09)
7/16/11: Bike – Long Ride (80.53 miles in 4:05:56)
7/18/11: Bike – Long Intervals (19.00 miles in 1:00:00)  
7/18/11: Swim – Endurance mile (1776yd in 29:48)
7/19/11: Bike – Hill repeats (23.00 miles in 1:15:01)  
7/19/11: Weights – Extreme Core I – 3 sets 
7/20/11: Swim – Train Smart Group Swim (3300m in 1:14:56)

* – I suffered an IT band injury about 6 miles into this run. I’ve been doing everything I can  since then to try and get to the point where I can run on it. I’ve been using lots of ice, my foam roller, had a deep tissue massage and I’m going to see my Physical Therapist today. I’m really bummed about not being able to run right now, especially when I only have about 4 more weeks of good training before Ironman!!

One Response to “Everything You Need To Know About Hydration”

  1. Mike July 21, 2011 at 2:52 AM #

    Thanks for the info and good luck next month!

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