Sports Nutrition: Beyond the Basics, by Linda Samuels, MS, RD, LDN

One Last Stop Before the Chicago Marathon… McDonald’s for salt packets

Bet you never thought a Sports Dietitian would ask you to stop at a fast food restaurant!  But for those of you who are “salty sweaters”, I am asking you to do just that.  Why?  Well, after you’ve ordered your Premium Grilled Chicken Sandwich – without mayo for those who need to watch their fat intake – please make a stop by the complimentary condiment stand and grab a handful of salt packets.   You have probably ignored these little salt packets your entire life, but they can very well play an important role in allowing you to complete your next endurance event.  But we’ll get to those salt packets in just a minute…

Marathons, and other endurance events like cycling and triathlons, have become wildly popular.  In Chicago, for example, we host the World’s Largest Triathlon, with almost 8,500 participants.  The Bank of America Chicago Marathon closed registration this year with 45,000 marathoners!  All these athletes have spent countless hours training, and learning everything they can about pacing, tapering and gear.  How many of these athletes know their sweat rate, though, and more importantly, how to use it?

Sweat rates measure an athlete’s sweat losses during exercise.  To measure your sweat rate, you would follow this procedure:    1- Take your pre-workout weight and subtract your post-workout weight for your weight loss factor (175 – 173.5 = 1.5 lbs); 2- Convert your weight loss factor to net fluid loss factor by multiplying the weight loss by 16 (1.5 lbs x 16 (fl oz/lb) = 24 oz;  3- Add ounces of fluid intake during workout to give gross fluid loss (24 oz + 20 oz = 44 oz);  4- Divide your gross fluid loss by your workout time in hours, to give you your sweat rate per hour (44 oz / 1.5 hrs = 29 fl oz / hr).

Typically, sweat rates are used to develop highly individualized hydration plans.  As you can see, the individual in the example above is a profuse sweater.  He can quickly become dehydrated without taking in appropriate amounts of fluid.  But is hydration the only issue that this athlete needs to consider – No!  I’d like to take you Beyond the Basics:  let’s look at sweat rates, and the implications for those endurance athletes who produce profuse, salty sweat.

Now, please note here that I highly recommend that any athlete who is a “salty sweater” (those that have the crusty white film on their face/body/clothes after a long training session) should seek evaluation from a Sports Dietitian or a sports medicine physician.  These “salty” athletes are at higher risk for Hyponatremia, which is a very dangerous and potentially fatal condition, occurring, most often, during endurance and ultra-endurance events.

Hyponatremia is a very complicated physiologic condition, but simply put, it is when blood levels of sodium have become dangerously low.  Some of the symptoms of Hyponatremia can be nausea/vomiting as well as lightheadedness/dizziness, and swollen extremities.  I’ve had numerous clients who have described their experience as generally feeling “horrible and very weak”, “cloudy, unable to focus”, and with swollen hands, twice normal size.  If you’ve ever experienced these symptoms during endurance training or an event, combined with noticing the salty film on your face/body/clothes, you may have experienced  Hyponatremia.

So we know that one of the causes of Hyponatremia in endurance athletes, is profuse, salty sweating.  And we know that an athlete’s sweat rate is highly individual, and will change with the intensity of the exercise, and with different weather conditions.  But even those who know their sweat rates, and consume sports drink to their individualized hydration schedule, can be at risk if they don’t consume additional sodium to compensate for their sodium losses from sweat.

Sweat contains around 2.25-3.4 grams of salt per liter.  A liter is approx 4.2 cups, or about 33 oz.  Translation:  For every 2 pounds of sweat loss, your body is also losing a significant amount of salt.  Knowing your sweat rate in various weather conditions will allow you to then prepare for your hydration and sodium needs.  A Sports Dietitian can thoroughly assess your hydration and electrolyte needs, and develop a plan to help you meet these specific needs.  This plan should be adapted to your changing training schedule – what you need to train for a half marathon or Olympic triathlon can be quite different than your needs when you are training for a full marathon or Ironman event.  So, how do you begin to address this issue?

My first suggestion would be to add Sweat Rate tabs to your training log.  Post-It brand has tabs you can write on and stick to the page sides of your training log.  On a tab, you can write the Heat Index (temperature and humidity calculation you can get off NOAA.gov website, search bar: heat index calculator) and your sweat rate.  Then in the log you can document the specific info.  For example, a tab would say “106/29oz”, which would denote a sweat rate of 29 oz when the heat index is 106 (90 degrees F + 70% humidity).  You would continue to complete sweat rates under different weather conditions, so then you would have data points. Eventually, you will have enough data points so that you can create your own Sweat Rate Chart, for easy referral.   Acclimatization will also affect sweat rates, but this will give you a general rule of thumb.

My second suggestion for “salty sweaters” is when you know you are going to be sweating profusely, consume a salt packet under your tongue prior to starting the exercise, and at least each hour of exercise.  This is in line with recommendations given by Dr. Lewis Maharam, the Running Doctor from Runner’s World Magazine.  Each salt packet is approx. 1/8 teaspoon salt, which is about 287 mg sodium.  This salt intake should be in addition to the sodium contained in your sport drink, and you should shoot for a total of at least 1000 mg sodium per hour, as tolerated.  Some athletes will need much more than this, but a Sports Dietitian or Sports Medicine physician should be consulted if you are experiencing symptoms even with additional sodium consumption.  If you are racing in an event, go to the med tent immediately, and relay your symptoms and what you’ve consumed so that they can treat appropriately.

One more important thing to note when taking Sweat Rates – if you gain weight during exercise and experience swollen extremities, this also may be a sign of Hyponatremia.  The cause of this type of Hyponatremia is a bit different, but more evidence is pointing to elevated levels of ADH or anti-diuretic hormone (sometimes called vasopressin) in some people.  If you gain weight and have swelling during exercise, it is important to go see a Sports Medicine physician, and explain to him/her your symptoms.

So, for those profuse “salty sweaters” out there – the next time you visit your favorite fast food restaurant for the healthy options that they offer, don’t forget to grab some salt packets!  They will take your endurance performance Beyond the Basics.

Written by PPL Sports Nutritionist Linda Samuels, MS, RD, LDN