Thoughts on Sodium and Fluids

Recently, there has been a lot of discussions challenging the traditional advice on fluid and electrolyte consumption. Tim Noakes, Paul Laursen #1 #2, Loren Cordain, and Inside Triathlon say, "Drink to thirst and do not worry about replacing electrolytes."

They say that fluid, electrolytes, cramps, and dehydration are not well understood and no one knows exactly what causes muscles to cramp. Furthermore, controlled research studies have not found any significant differences in fluid or electrolyte profiles between athletes that cramp and those that do not. Researchers point out that the only muscles that cramp are the ones that are being exercised. If it was just a matter of dehydration or electrolyte imbalance, the entire body would cramp.

Lorain Cordain says that normal body sodium levels are 140 mmol/L. During exercise, if 1 liter of fluid and 60 mmol of sodium is excreted (typical amounts for "salty" sweaters) then the new sodium concentration is 142 mmol/L. Which is actually a rise in sodium concentration. He goes on to say that the best way to fix a cramp is to stretch it, not consume a sports drink. Therefore he reasons that dehydration and electrolytes are not the real cause of cramps. When examining actual race results, the American College of Sports Medicine may suggest limiting body weight loses to 2%, but many athletes continue to perform at very high levels with body-weight losses of 3% or even greater. In fact, it is often the most dehydrated athletes in a race that typically finish first.

Haile Gebrselassie and Alberto Salazar are two perfect examples of athletes who have high sweat rates yet performed extremely well. Some argue that having a high sweat rate is actually a benefit. During races, "heavy sweaters" are better able to cool their body. There is also the issue of the source of fluid losses. Some of the losses occur as a result of water being released during the utilization of glycogen while the rest of the losses come from extracellular fluid. Intracellular fluid, however remains the same.

So What Causes Cramps

• Poor posture or inefficient biomechanics affects the "strain gauges" in muscles. 
• Cramps result from the breakdown of protein for fuel when carbohydrates are not readily available. 
• Engaging in an activity or with an intensity or duration that one is not prepared for.

What To Do

• Cordain suggests to reduce your intensity, stretch, and consume some carbohydrates. 
• Dr Noakes suggests placing salt on the tongue to reduce cramps. It tricks the brain and the cramps go away. The same phenomena has been shown with placing carbohydrates in the mouth and receiving a short term boost of energy. It's not so much the physiological benefits of these substances, but how much the brain dictates performance. 
• See your high sweat/salt rate as a positive. Tell yourself you're better equipped at cooling your body. 
• Don't rely on the thirst mechanism, consume 20-40 oz per hr. I believe we're too distracted and ignore signs of thirst during a race. We do need fluid to digest the calories we consume. Also, if you find yourself belching, drink water to help with digestion.
• Consume 400-800 mg sodium per hour when racing over 4 hours. From what I have read and experienced, it will not harm performance and it may enhance nutrient absorption. I also believe that we need some sodium to balance out the large amount of fluid we consume during long races. For athletes, such as my wife, who drink a ton of water it may also help minimize the risk of hyponatremia.
• As always practice, to train your body as well as find out what works best for you.

Daily Sodium Intake

• If you are following a low carb high fat diet, you may need to increase your daily sodium intake to compensate for a reduction in blood pressure. 
• Research has revealed that increasing fruit and vegetable consumption can completely offset the negative effects of dietary sodium. The positive benefits seem to be from the high potassium levels in fruits and vegetables that leads to a better sodium/potassium ratio.