Let’s talk about electrolyte replenishment during long runs and races. As runners we all sweat to some degree. Amazingly, each person has around 100 sweat glands on a quarter sized area of your skin for a total of 2.6 million total sweat glands. The amount we sweat depends on our gender, fitness level, weather conditions, altitude, and a few other factors.

Our bodies are designed to effectively keep a stable body temperature which can present a challenge during prolonged running, especially in warm conditions.

The Importance of Electrolyte Replenishment

The hypothalamus is the area of our brains that detect changes in body temperature. Our muscles work like furnaces and when the body temperature rises, the hypothalamus detects the increased temperature of the blood and the higher core temperature. Body temperature can rise as much as three degrees during exercise and this causes the body’s natural cooling system to kick in to lower the temperature back to normal.

Blood circulating near our skins surface pushes fluid out of our sweat glands where it cools (called thermoregulation) and the evaporating fluid draws heat away from the blood vessels. The cooler blood then circulates through the body and lowers your overall temperature.

The bottom line is that sweating is a healthy and necessary function. The human body is composed of between 60-75% water and that’s one reason why fluid balance is vital for helping us function at optimum levels.

In addition to regulating body temperature sweating helps clean out our pores and release toxins. With increased sweating the blood becomes thicker which makes the heart work harder to circulate blood throughout your body. If fluids are not adequately replaced dehydration can occur. We also need to replace electrolytes along with fluid during extended periods of exercise.

What are electrolytes?

An electrolyte is a compound which produces ions when dissolved in a solution like water. Electrolytes have either a positive or negative charge and this ionic effect is what allows them to carry electrical energy (which is why they’re referred to as electrolytes). In terms of our discussion about sweating and hydration we’re referring to minerals that are dissolved in the body’s fluids, specifically the most important ones including sodium, potassium, calcium, magnesium, and phosphate. (1)

What do electrolytes do?

Magnesium, calcium, sodium, and potassium are all critical to body functions, particularly for the muscle and nervous tissue. They also help maintain the body’s fluid balance and help control the body’s ph. Having too much or too little in relationship to each other can lead to muscle spasms, decreased performance, and pain. Dehydration with severe electrolyte imbalances can even lead to death. Overhydration (also known as hyponatremia or low sodium) can also be fatal.

How many electrolytes do we need?

Most people get enough electrolytes through food when they consume a healthy balanced diet. However, there have been studies that show that many adults are deficient in magnesium. Magnesium is needed for maintaining a healthy blood pressure, muscle and nerve function, regulating blood sugar, bone development and around 300 other cellular functions. If you’re highly active it may be beneficial to supplement your diet with 400 mg of magnesium.

We lose electrolytes through our sweat and need to be conscious about replacing electrolytes during prolonged exercise, especially in the heat or at higher altitudes. In a liter of sweat the average person loses 13 mg of magnesium, 15 mg of calcium, 200 mg of potassium, and 900 mg of sodium. Some people excrete more electrolytes in their sweat (salty sweaters) and this can be seen by the white crusty streaks on their face and body. Some runners are simply more prone to electrolyte imbalances. Studies also show that you’re going to lose more electrolytes if you’re unfit or not acclimatized to the weather or altitude conditions.

Signs that you’re low in electrolytes

Some of the main signs of an electrolyte imbalance can include decreased performance, muscle cramping or spasms, muscle weakness, decreased or dark urine, dizziness, fatigue, nausea, constipation, dry mouth, and dry skin. However, a large majority of muscle cramping is probably due to lack of muscular fitness and may not be directly linked to your electrolyte balance. Pay special attention to your urine. If you’re going 5-6 hours between urination or the color is darker than light yellow or if the amount is scanty then you’re not adequately hydrated. (2)

How you should replace electrolytes

Most people’s diets contain more than adequate amounts of sodium so when you’re looking to replace electrolytes you don’t want to only replace sodium. Sodium by itself causes water retention (and not necessarily in blood volume). Too much sodium while running can also leach water out of your system and dump it in your digestive tract which can cause a sloshing feeling in the stomach (this feeling can also occur if you consume a too much fluids all at one time). You’ll often notice swelling of the hands, feet and ankles if sodium is out of balance. The focus with electrolytes is replenishment, not replacement.

During your training period you should experiment during your long runs to dial in your hydration and electrolyte needs. I recommend choosing an electrolyte product that has a balance of sodium, potassium, calcium and magnesium. Electrolytes enter your system fairly quickly so taking an electrolyte supplement a few minutes before your race (and even midway through) would be a good idea.

Sources:
(1) www.scientificamerican.com/article/what-are-electrolytes/
(2) www.runnersconnect.net/electrolytes-for-runners/

Quick Tip:
This topic was covered in the quick tip segment of episode #261
www.marathontrainingacademy.com/the-jungfrau-marathon