HYPONATREMIA - TOO MUCH FLUID; TOO MUCH SWEAT
Slower Runners, Please Take Note
By Mindy Solkin
Owner and Head Coach
The Running Center
The sport of running and particularly marathoning has come a long way since Frank Shorter made America proud by winning the Olympic Gold medal for the marathon in the 1972 Olympics. With it came the first running boom, and participation from mostly college and post-collegiate men who posted fast times on the road and the track. The word "aerobics" was a newly coined word, having gained its roots from Kenneth Cooper's 1968 breakthrough book entitled Aerobics. But these fast runners were not into the sport for the fitness of it all; rather they were competitors and their chosen competition was the road race, and more specifically, the marathon.
Fast forward to the mid 1990's. The word "fitness" had replaced the word "aerobics" to encompass an entire industry and a new generation of both men and women who were bent on improving their health, weight, body image and social life. But with this also came many people who were not fit, or at least not "running-fit", but nonetheless were committed to training for, and running in a marathon. These new converts created the second running boom and flooded the roads and trails to reap the benefits of what the first running boomers had created. However, this new runner was mostly a participant, not a competitor, and thus their finishing times were not as important to them. The mere fact that they finished was their victory.
Obviously, slower finish times mean that this participant will be running for a longer time, in some cases twice as long as their faster mentors. Being on the course longer requires the intake of important nutrients to replace what has been expended. Those told to drink water at every water stop may find themselves with a condition known as hyponatremia, a condition that occurs when plasma sodium levels fall dangerously below normal, hence water intoxication. A more scientific definition is when there is less than 135 millimoles of sodium per liter of plasma. Normal values range from 142 to 138. Symptoms usually begin at values below 130. If below 120, there will be massive brain swelling and the condition can be fatal.
CAUSES AND FACTORS
There are two causes of hyponatremia: consumption of too much fluid over too short a time span and inordinate sodium loss through bodily sweat. If both factors are present, the risk is exacerbated. It is true that those who sweat at a higher rate are at a higher risk; however excessive fluid intake for a normal sweat rate can also lead to inadequate fluid loss and therefore hyponatremia as well. If a person is overdrinking-that is, not using the amount of water they are consuming for their level of exertion-they will dilute their plasma sodium concentration and be more prone to the condition. Smaller runners are more at risk, therefore many women should take extra care. In addition, women lose more sodium than men and they start out with about 10 percent less body water. Slower runners, say over four and a half hours, are at increased risk since their exertion levels do not justify all the drinking they are doing before, during and after the marathon. This is not to say that they shouldn't be well-hydrated when they get to the starting line, but that they need to be aware of their body weight, projected finish time and individual needs.
Early signs that you may be hyponatremic include feeling bloated, followed by nausea and vomiting. Look for the inability to rotate a ring on your finger or a lack of "play" in your wristwatch. High blood pressure and headache often come next. In more severe cases feelings of restlessness, lethargy and confusion can appear. At this level, respiratory distress and seizures may occur and the most advanced stages include coma and possible fatality.
PRECAUTIONS & TREATMENTS
The body expels excess water through urine, usually at a maximal rate of about one liter per hour. During a race, urine production decreases 20 to 60 percent due to a decrease in blood flow to the kidneys, as it is redirected to the working muscles. If you're especially nervous or running in hot weather, the decrease will be on the higher end of this estimate. So a good starting point is to expect to lose perhaps two percent of your pre-marathon body weight. Any more and you are dehydrated; any less and you may be hyponatremic. Gaining weight is a sign that you are overdrinking. Ideally you should keep tabs of your weight throughout your training, and then especially weigh yourself on marathon morning. You can then record your pre-race weight on your bib number. Of course this means that marathon management will need to install scales along the course, either at the medical stations or at the toilets.
Drinking and eating salty foods during the race such as sports drinks and salty snacks (crackers, pretzels) will replace lost calories, electrolytes and carbohydrates. The hotter and more humid the weather, the more salt you should consume. Keep in mind that up to two pounds of water weight will be retained from your carbo-loading dinner the night before the marathon. This should factor into your pre-race weight, so extra sodium will be needed to compensate for the water retention. Finally, your urine should be free-flowing and a pale yellow color, not completely clear. If it is dark and concentrated, with little output, you are dehydrated. Perform a test-trial during your long training runs. Set up your own system so that come marathon day you will be able to perform at your best, knowing that you have covered your bases to eliminate hyponatremia.
© 2004 The Running CenterTM All Rights Reserved
Mindy Solkin is the Owner and Head Coach of The Running CenterTM. She is
certified by USA Track & Field (USATF) as a Level III Running Coach (the
highest level) and by the American Council on Exercise (ACE) as a personal
Known as "Coach Mindy" to her runners, she has coached thousands of people
over the past ten years, helping them to achieve their goals on the open
roads and the winding trail, whether it is running their first mile or
pursuing their personal best in the marathon.
Mindy was the creator of the Leukemia-Lymphoma Society's Team In Training
marathon program in New York City and served as its Head Coach from 1994
through 2001. From 1995 through 2002 training over 3,000 runners to run marathons in cities around the world, Mindy was the Head Coach at Reebok
Sports Club/NY. She is also the creator of the Polar Heart Bra® and has been
a PowerBar® Team Elite athlete since 1994. She can be reached at www.TheRunningCenter.com.