Sweat and Sodium - by Andy Baldwin

My buddy Martin completed a 20 mile training run last weekend in preparation for the Comrades Ultramarathon race we are doing in South Africa in May (www.comrades4thekids.org). On Monday he called me in frustration because despite taking in lots of Gatorade, water and Energy Gels along the way, he suffered from debilitating muscle cramps in his legs for the last five miles of the run. “What the heck is going on Doc? How am I going to make it through 56 miles if I can hardly make it through 20 miles?” Martin explained to me that he was coated in salt at the end of his run and had gone to the bathroom after the run and that has urine was clear in color so he assumed he was adequately hydrated. I told Martin I would think about it and get back to him and not to fret.

That evening I went to my usual Monday night yoga class. About halfway through, I succumbed to the cramp monster as well. Dripping sweat and struggling to hold a contorted pose, my right hamstring seized up and then my left foot cramped up. I swore and fell out of the pose. As I massaged the cramp I made a decision that I would write my blog this week about muscle cramps, what causes them, how to prevent them and how to deal with them. We have all had a muscle cramp before (or at some point will). Muscle cramps are extremely frustrating but relatively easy to prevent.

So what causes muscle cramps? The three most common factors that lead to muscle cramping are: fluid loss, muscle fatigue and loss of sodium. Based on the fact that Martin’s urine was clear after his long run tells me that he did maintain good hydration throughout. So dehydration most likely was not the cause of his cramps. What stood out most to me in Martin’s run recap was his observation that his body was coated with salt afterwards. Sweat sodium concentration and sweat rate can vary greatly from person to person. Athletes who look like they’ve been rolling around in the salt flats of Utah every time they finish a workout suffer huge sodium losses. Studies have shown that “salt-cakers” are much more prone to muscle cramps during exercise. On the issue of muscle fatigue, a muscular endurance or power demand greater than usual for that person will predispose to cramps. When a person’s calves are firing stride after stride for hours on end paired with sodium loss, or the body becomes dehydrated and is attempting a tough muscular feat, muscle cramping will often occur.

Sodium is an important element in initiating signals from nerves and actions that lead to movement in the muscles. A sodium deficit makes muscles “irritable” and with just the slightest stress may cause the muscle to contract and twitch uncontrollably. For many years, athletes have attributed cramping to depletion of potassium or other minerals like calcium and magnesium from the body. However, recent studies have shown that the level of these elements lost in sweat is minimal. Sodium is the true culprit. Those people who work in hot environments and sweat abundantly lose sodium and must replace it if they are to avoid a cramping result. The average person sweats about 1-2.5 liters per hour, while someone with a high sweat rate will sweat approximately 3.5 liters per hour.
To figure out how much you sweat you need to weigh yourself before and after your average workout. Remember that sweat soaks into your workout clothes, so you will need to weigh yourself without clothes to get an accurate measurement. Every pound of weight lost is equivalent to a ½ liter of sweat. Be sure to take into account the amount of fluid you took in during the workout. Now you have your sweat rate. This is the amount of fluid you need to drink to stay hydrated. But this is only half of the solution. A person needs a sufficient amount of sodium in their system along with this fluid replacement to prevent cramping. The average person takes in only 4 grams of sodium in their diet each day. Over the course of a 2-4 hour exercise session (long run, triathlon, long yoga), this means one could lose over 9 GRAMS of sodium! This is the reason why some people look like they’ve been playing in a sandbox when they get done with an endurance workout.

For most athletes, simply adding salt to the diet and drinking an electrolyte sports drink will be sufficient. But for those athletes that are salty sweaters and prone to cramping, the concentration of sodium in sports drinks simply is not enough. More sodium supplementation is necessary for them to keep up with the amount they are unloading. Here are some suggestions:

• Add more salt to your sports drink. 1/2 a teaspoon per liter is a convenient and efficient way to get at least an extra gram of sodium into your diet

• Salt pills work too, but it is imperative to drink adequate fluids at the same time. They are much more effective and better tolerated if they are ground up and mixed with an appropriate amount of fluid (2-3 tablets per liter of fluid)

• Using prepackaged electrolyte mixes, such as Endurolytes, GatorLYTES, or ELOAD to ensure that you are consuming the right amount of sodium

• Consider eating the following high sodium food items before or during extended exercise (amount of sodium per serving)

o Chicken Noodle Soup 1100 mg
o Dill Pickle 1000 mg
o Tomato Sauce 1500 mg
o Cheese Pizza 700 mg
o Pretzels 500 mg
o Tomato Juice 900 mg
o Gatorade 110 mg
o Powerade 55 mg

Be sure to experiment with altering salt intake before a race so you are sure you can tolerate your food and beverage choices. For those people with normal blood pressure, an increased or even excessive sodium intake should not pose any health risk. For those people with elevated blood pressure sodium intake and BP should be more closely monitored.

Quick Fixes for Cramps
When cramps strike during a workout or competition, take immediate action with the following steps:

1. Stop and Stretch. Cramps are often related to changes in weight bearing on a muscle, therefore passive stretching and non weight-bearing exercises may help.
2. Massage the area. Rubbing the cramped muscle may help alleviate the pain as well as help stimulate more blood flow to the area.
3. Stimulate recovery. Rest and adequate rehydration with fluids containing electrolytes, particularly sodium, will help reestablish the muscle to normal working status.

In summary, large sweat loss means extensive sodium loss. Sodium loss can result in incomplete rehydration and sodium deficiencies, and may predispose you to muscle cramps.

Martin, eat more pretzels and dill pickles man!