Electrolytes and Nerves

My girlfriend & I have joined forces on an e-book geared towards providing anyone walking into a Bikram yoga class, whether it’s their first time or they’ve been doing it for a while, with basic information about how their body functions when exercising in intense conditions, and what they need to know to take proper care of themselves.

(My girlfriend is a professional yoga teacher, and blogs at: http://yogamattes.com )

You can see the chapters on sweating and hydration in older posts, on my blog or hers. Again, these are chapters from an e-book geared towards hot yoga class, but the information in it is applicable to all kinds of athletes. We’re writing this guide from our experience in hot yoga, but we’re not just hot yogis—we’re hot no matter what we’re doing. (Har, har. See what I did there?) Anyway, here is some basic information about maintaining electrolyte balance, and what those electrolytes are actually doing in your body.

Chapter 3: Electrolytes

Balancing your hydration level is about more than just water. When thinking about sweat-loss and water intake, you also need to think about electrolytes. Your body’s nerve reactions and muscle functions depend on the proper concentration and exchange of these chemicals.

What exactly are electrolytes? Chemically, they are substances that ionize in solution (that is, dissolve in water) and acquire the capacity to conduct electricity. Some of the specific ones that are commonly measured by doctors are: sodium, potassium and chloride. These substances are lost through heavy sweating—and if you rehydrate with only clear water, then your electrolyte levels will be thrown out of balance; the ratio of water to electrolytes in your body will be altered.

Sodium is a majorly important positive ion in the fluid outside of cells (the interstitial fluid, like we talked about above.) The chemical notation of sodium is Na+. You know sodium best after it’s been combined with chloride—that’s the chemical composition of table salt.

Sodium regulates the total amount of water in the body, and the transmission of sodium into and out of individual cells plays a vital role in critical body functions (as we’ll see when we talk about nerve impulse conduction below.) Many, many processes in the body and brain require the conduction of electrical impulses for communication, integration and control, and the movement of sodium (a positive ion) is essential in generating these electrical signals. Therefore, too much or too little sodium leads to cell malfunction.

Potassium is a major positive ion found inside of cells (it’s chemical notation is K+.) Proper potassium level is essential for normal cell function—among many other things, it regulates heartbeat and the function of the muscles. A serious disruption of potassium levels can critically affect the nervous system and increases the risk of irregular heartbeats (arrhythmias.)

Hypokalemia is a decreased level of potassium. It can be brought on by kidney diseases, or excessive loss due to vomiting, diarrhea, or—most relevant to our subject—heavy sweating.

Chloride (Cl-) is a major negative ion found in the fluid outside of cells and in the blood. It is closely regulated by the body, and plays a role in maintaining a normal balance of fluids. Just like all the other electrolytes, it can be thrown out of balance by various diseases, but, relevant to our discussion, excessive loss can occur through heavy sweating.

Symptoms of Electrolyte Imbalance

An electrolyte imbalance can create a number of different symptoms—and the specific symptoms that manifest will depend on which of the electrolyte levels are affected. Altered potassium, sodium, magnesium or calcium levels can lead to: muscle spasm or cramping, weakness, twitching and convulsion.

When the levels are low (the more likely scenario in a Bikram Yoga class, as opposed to high,) it can cause: irregular heartbeat, confusion, blood pressure changes, headache, dizziness and nausea.

In a hot yoga or Bikram Yoga class, by far the most common signs of electrolyte imbalance will be headache, dizziness, nausea, and cramping.

Replenishing Lost Electrolytes

So we know now that these ionizing substances are essential for a host of critical body functions, and that they are lost during heavy sweating, potentially, and very likely, to the point of excess. So the next step, logically, is to replace the lost electrolytes and maintain the balance. The best way to do that is with consistent intake of electrolytes.

A good rule of thumb to follow: drink your water with electrolytes. Don’t just chug clear water before, while, and after sweating heavily—replenish your lost water and your lost electrolytes together by adding sources of electrolytes directly to your water. As one example: try clear water with added raw honey to taste, a pinch of unrefined salt, and freshly squeezed lemon juice. Take this concoction with you into class—steadily replete both your electrolytes and water together, even as you deplete them through sweating.

When, during or after class, you need an extra boost of electrolytes, supplementation is appropriate. If you experience symptoms of electrolyte imbalance as you practice, you should seek out some concentrated source, such as electrolyte-replenishment packets (like “Emergen-C” or “Ultima,”) or simply a small pinch of sea salt dissolved on the tongue.

Meanwhile, take electrolytes in steadily through diet in your daily life. Don’t rely on concentrated supplementation alone. What that means is, if you do something that causes you extreme electrolyte depletion all the time—like sweating heavily in a Bikram yoga class several times per week—take the initiative. Take steps to prevent imbalances in the first place. You should always be attempting to take in replacement electrolytes at a steady pace throughout your daily life—not only in occasional concentrated mouthfuls after you have already realized the balance is drastically off. This is done through a diet rich in electrolytes. For instance, you know you’re going to consistently lose potassium through sweat in class—so take it in just as consistently, from dietary sources like bananas or coffee. Or whatever—just find sources that work for you and make electrolyte replenishment a dietary priority.

Electrolytes should be taken in in the same consistent, gradual, measured way that you supply your body with water. You know you lose a great deal of water in class, so you consistently take in reasonable amounts of water during the day, every day. In other words, you keep hydration in mind even when you’re not dehydrated. In the same way, keep electrolyte balance in mind, even before you experience symptoms of imbalance.

Extra Notes on Sodium

Sodium warrants special attention for a couple of reasons. One, it is among the main electrolytes lost in sweat (hence sweat’s salty taste.) Two, you generally don’t get much of it from commercially available electrolyte drinks and powders. As a result, you may be taking in a healthy amount of other electrolytes, but, because you are losing so much through sweat and taking in so little through electrolyte drinks or powders, you may still fall short of replenishing lost sodium.

General medical guidelines for low sodium levels recommend restricting fluid intake in order to prevent hyponatremia (too little sodium in the body, relative to water,) but in the context of Bikram Yoga practice, limiting fluid intake is not appropriate. That guideline is general, and does not apply to anyone who regularly loses huge amounts of water through sweat. In the case of low sodium-concentration brought on by massive loss through sweating and dilution by clear water intake, the solution is, logically, increased intake of sodium. A pinch of salt on the tongue, a pinch of salt added to your water, a sprinkling of salt on your food after class. However you take it in, you will need a little boost of sodium to properly replenish what you lose while practicing, before you’re ready to go into the room and sweat again.

Special Concerns 

Certain medications may cause electrolyte imbalances, such as: chemotherapy drugs, diuretics, antibiotics and corticosteroids. If you are on any of these medications, it is important to keep track of your electrolyte levels. Make sure your doctor knows you are practicing hot yoga and understands how much heavy sweating is involved.

Chapter 4: Nerves

Electrolytes are essential for generating the electrical impulses that facilitate the nervous system’s communication and control. How exactly does that work? We’ll take a short, simplified look at it, to a) illustrate how the electrolytes we’ve discussed actually function by conducting electrical impulses and b) to set the stage for the next chapter, wherein we’ll look at the nervous system. There are two main types of cells in the nervous system—neuroglia and neurons. Neurons are the one we’ll be considering here. They can be afferent (conducting impulses towards the brain) or efferent (conducting impulses away from the brain.)

A neuron consists of a cell body (also called the soma or perikaryon,) the axon, and one or more dendrites. The dendrites of a neuron are processes that stick off and branch like tiny trees (in fact, the name comes from the Greek word for tree.) The dendrites receive impulses to conduct from other neurons. Once received, the impulse travels down the axon—a long process, like a thin tail—and reaches the next neuron by way of terminal branched filaments called telodendria. Axons can vary in length from a meter long to a few millimeters. They also vary in width—from about 20 nanometers down to a single nanometer.

In order to understand how impulse conduction works, and how electrolytes are involved, it pays to get familiar with a few relevant terms.

Potential difference—an electrical difference, or an electrical gradient. A potential difference is the difference between the electrical charge present at two points. A potential difference is a form of potential energy. It is a force that has the potential to move positively charged ions down an electrical gradient, that is, from a point of higher positive charge to a point of lower positive charge.

Polarized membrane—a membrane whose outer and inner surface have different amounts of electrical charges. Basically, a potential difference exists across a polarized membrane.

Depolarized membrane—a membrane whose outer and inner surface have equal amounts of electrical charge. A potential difference does not exist across a depolarized membrane; it is zero.

When a neuron is not conducting, the inner surface of its membrane is slightly negative to its outer surface. There is a potential difference across its membrane—in a nonconducting neuron, this is called “resting potential.” The mechanism that creates this resting potential is primarily a sodium-potassium pump, built into the neuron’s plasma membrane (the outer membrane of the neuron.) This pump actively transports positive sodium and potassium ions through the plasma membrane in opposite directions and at different rates. For every 3 sodium ions it moves out, it moves 2 potassium ions in. If, for instance, it pumped 100 potassium ions into a nerve cell from the extracellular fluid, it concurrently pumps 150 sodium ions out of the cell. This makes the inner surface of the neuron’s membrane slightly less positive—or, slightly negative—to its outer surface.

Blamo—there you have the potential difference in a nonconducting neuron known as resting potential. Now, an impulse comes along for the “resting” neuron to conduct.

1) When a sufficient stimulus is applied to the neuron, it vastly increases the permeability of its membrane to sodium ions at the point of stimulation (it lets more sodium in.)

2) The positive sodium ions rush in towards the point of stimulation. The excess of sodium outside the membrane, therefore, diminishes. It quickly reaches zero. In other words, the stimulated point of the membrane is no longer polarized. But only for an instant. Quickly—within milliseconds—the positive sodium ions streaming in create an excess of sodium inside the cell and trigger an action potential. An action potential is a potential difference across a neuron’s membrane with the inside positive to the outside. So, since resting potential has the inside negative to outside, action potential is a reverse polarization. The inside becomes positive to the outside. Development of action potential at the stimulated point of the neuron marks the beginning of impulse conduction.

3) A chain reaction occurs. The action potential of the stimulated part of the membrane becomes the stimulus for the adjacent part of the membrane, and that next stimulated point goes into the same process. The action potential moves along the length of the neuron, point by point, conducting the electrical impulse on to its destination.

[Next up, the nervous system and the fight-or-flight response.]

---