Sometimes when writing EndurElite articles, my hands cramp up. This could be due to my advancing age, the fury with which I mash my fingers into the keyboard, or some run-of-the-mill overuse, but it is definitely NOT because of an electrolyte imbalance. Not because typing awesome articles isn’t making me break out into a hot sweat – it is, but because electrolyte balance does not (usually) cause muscle cramps. That’s right. It’s one big misconception.
What Causes Muscle Cramps
Note that I said (usually). This is to be scientifically accurate. On seldom occasions, one can suffer from muscle cramps due to electrolyte depletion. However, this is a seldom occasion, and it is NOT what we often suffer from following a long run. If caused by electrolyte depletion, muscle cramps usually affect the entire body, not just one muscle. There is also more to consider than just sodium and potassium. Calcium, phosphorus, magnesium, chloride, and other electrolyte minerals would be depleted alongside sodium and potassium if cramps were due to systemic electrolyte depletion. The primary point being that your typical sports drink or salt supplement would not affect muscle cramps, as they usually only contain 2-3 electrolytes.
Athletes that get muscle cramps are not suffering from poor hydration, sodium, chloride, or calcium status at the time the cramp begins, and athletes with a history of exercise-associated cramping are not salty sweaters. It could be that sodium, chloride, and/or calcium are not the primary electrolytes involved. Anecdotally, I find magnesium to help me personally, but the existing literature on the topic only mildly supports magnesium for the prevention of muscle cramps. Interestingly, however, magnesium is not just involved in fluid and electrolyte balance. It is an important mineral for nerve transmission, muscle contraction, and muscle relaxation.
The types of cramps typical of exercise are most likely due to nervous system “malfunctions.” Essentially, the neuromuscular theory of exercise-associated muscle cramps states that with prolonged, repetitive exercise (running, cycling, swimming, pretty much any endurance sport!), localized muscle fatigue causes cramping by increased muscle excitability. Muscle excitability can be thought of as a muscles responsiveness to input from the nervous system. This has much to do with the golgi tendon organ.
The golgi tendon organ senses muscle tension and essentially stops us from hulking out and tearing a muscle by squeezing so hard. It sounds like some idea from a comic book, but it’s true, and we can override the limits of a golgi tendon organ via training and high amounts of adrenaline. One example of overriding the golgi tendon organ is called “hysterical strength.” These are true stories of the fight-or-flight response (hysterical strength) overriding this governing mechanism. Tom Boyle witnessed a boy get struck and pinned by a sedan. Boyle ran over, tipped the car, and the boy escaped. The feats can be even more extreme when a trained strength athlete panics. An offensive lineman once lifted a 3,500 pound car off of a tow truck driver trapped underneath the wheel. He had to actually lift the car from the ground, not just relieve some compression on the suspension!
The football player and the man that was trapped both escaped okay, but overriding the golgi tendon organ in extreme situations can result in muscle tears or other injuries for the hero unaccustomed to such extreme mechanical stress. Tom Boyle, clenched his jaw so hard, he broke eight teeth. When cramping occurs in runners or cyclists, the golgi tendon organ is desensitized from the, usually low-load (bodyweight), exercise, thereby allowing the muscle to contract more and more. At the same time, the nervous system continues sending electrical signals to the muscle because the brain is telling the muscles to move the body closer to the finish line. Those with a history of cramping have increased electrical impulses, even at rest. This is why stretching helps. It places some tension in the muscle, reactivating the golgi tendon organ. So anyway, what is the purpose of electrolyte for athletes?!
Electrolytes Maintain Hydration
You might be thinking, “Duh! I already know that!” The effects of electrolytes are a little more important than just accompanying water and carbohydrates into the body. Keeping water in the body is just as important as sweating it out. Maintaining fluid increases the ability to cool by sweating as well as reducing rates of temperature change, as water is very good at maintaining a constant temperature. If we were not made of 60% water, going outside on a sub-freezing day could quickly result in our frozen demise. Electrolytes also maintain blood volume. When we lose blood volume due to sweating, heart rate must increase to continue delivering oxygen to working muscles. However, increased heart rate means that the heart is working harder, which will decrease our performance. Let’s go over each of the major electrolyte minerals and their function in an exercising person.
Sodium
Sodium (Na+) is the primary extracellular electrolyte mineral. Therefore, it is more susceptible to being lost in sweat. This has resulted in sodium receiving most of the attention for electrolyte minerals. The major fear is hyponatremia (low blood sodium), which can have very severe effects, including death. Hyponatremia can occur from extensive dehydration or over-hydration if drinking only water or another drink containing no sodium. In ultramarathons, about 30% of runners finish the race in the hyponatremic state. Those with hyponatremia also appear to have ~50% more muscle damage and 30 minute slower completion times than normonatremic runners in a 161 km race. Sodium also helps limit post-race fluid losses to accelerate rehydration by reducing urine output. As the most studied electrolyte, sodium also helps maintain blood plasma volume, which increases blood flow to the skin surface, where it can be cooled and better regulate body temperature, heart rate, and performance.
Potassium
Unlike sodium, potassium (K+) does not have regulatory mechanisms in place to limit losses in sweat, and high sodium intake without potassium accelerates potassium loss. Potassium complements sodium as the primary intracellular electrolyte mineral, and being inside the cell helps limit how much is lost in sweat, which is not much. We (Matt and Jordan) have actually studied rehydration beverages capacities for rehydration following a dehydration protocol. A beverage containing no carbohydrate but more potassium (and magnesium) sped rehydration compared to a very popular carbohydrate-electrolyte solution, which was actually not different from flavored water. While the water had small amounts of electrolyte, the study suggests one and/or two things: 1) more diverse electrolyte profiles (i.e. including magnesium/calcium) are required for adequate rehydration, and/or 2) only a small amount of electrolyte is required for rehydration. Potassium may be even more important than sodium. We require nearly double the amount of potassium than we do sodium, and potassium actually regulates sodium excretion, which is the true mechanism of blood pressure control (there’s a little #FastFact for you!).
Chloride
Most drinks have chloride (Cl-) because they add sodium in the form of salt, sodium chloride (NaCl). Like sodium, chloride is subjected to depletion with fluid loss. Chloride is the body’s most abundant negatively charged electrolyte (sodium and potassium are both positive). Chloride doesn’t receive as much attention as potassium or sodium, but chloride is literally what keeps those two in check by maintaining electrical balance (or imbalance if needing to send an electrical signal). Hypochloremia (low blood chloride) has the same dangers as hyponatremia, and for every 10 sodium ions lost in sweat, 8 chloride ions go with it. Therefore, chloride is an electrolyte that must be considered during exercise.
Calcium
Like potassium, only small amounts of calcium (Ca+2) are lost in sweat. Calcium is the most abundant electrolyte mineral in the entire body, mostly stored in bone (99%). Bone health relies on calcium as well as vitamin D, not just one or the other. However, calcium is second only to iron for inadequate intake in athletes. This can be a concern for endurance athletes, particularly for females who are predisposed to poor bone health, because exercise increases all nutrient demands, including calcium, which is also excreted at higher rates in athletes. Muscles require calcium for contraction and movement, so when they don’t have enough, they siphon it from bone. Calcium may not directly affect hydration status. However, it is critical for glucose and fat metabolism, exercise performance, and body composition. Those with higher dairy and calcium intake consistently demonstrate a leaner body composition. Non-competitive athletes supplementing the recommended daily intake (1 g) of calcium per day for four weeks increased fatty acid oxidation during submaximal exercise, improved both 10 and 25 mile cycling time trial performance, and decreased body fat.
Magnesium
Magnesium (Mg+2) is the most ubiquitous mineral in the human body and the fourth greatest in terms of quantity. Magnesium is very similar to calcium in function, as both carry a +2 charge. Unlike other minerals, magnesium actually has some evidence to say it can alleviate cramping. Although, some other studies have not found it efficacious for that purpose. Supplemental magnesium may help athletes or pregnant women with cramping, while not helping those with idiopathic muscle cramps. This is likely because athletes and pregnant woman have increased magnesium needs that they are not meeting via their diet. While magnesium can cause intestinal discomfort, yet chelated magnesium does not because it is the form found in foods and quickly absorbed. Magnesium is currently known to participate in over 325 enzymatic reactions, many of which are related to exercise and performance: generating ATP, muscle contraction and relaxation, lipolysis, cardiac activity, bone metabolism, and more. Magnesium deficiencies can impair carbohydrate metabolism, reduce insulin sensitivity, and increase blood pressure.
Does that lead to reduced athletic ability? Despite its abundance, the USDA reports that 60% of Americans do not consume enough Magnesium, and this is even more pronounced in runners (particularly women). In a study featuring female cyclists, they consumed a diet containing 100mg magnesium with 200mg supplemental magnesium, then stopped taking the supplement for one month. In the third month, they resumed use of the supplement. Between each month, they participated in a monitored exercise tolerance trial. After the month without the supplement, the cyclists had compromised metabolic efficiency and exercise capacity. Conversely, other investigations on supplementing magnesium indicate that magnesium may increase peak oxygen consumption and total work output while decreasing heart rate during exercise. Magnesium is a magnificent mineral for athletes. That’s why it’s the only one that gets 2 paragraphs!
Electrolytes in Sports Drinks
Clearly, electrolytes should be contained in sports drinks. The tricky part is determining how much the athlete needs. For minerals lost in sweat (sodium and chloride), this is largely dependent on the individual athletes. For calcium, magnesium, and potassium, it depends on the quality and quantity of the athletes’ diets. However, it’s likely that the diet can be improved. Sodium needs during exercise range from 100 to 2,500 mg per hour! This indicates that someone is either really going to need an electrolyte (salt - NaCl) supplement, or they are barely going to need to think about it at all, as any quantity of sodium will keep them from dangerously low levels. Therefore, a sports drink really isn't the best suitor for electrolyte replacement. Yes, it should contain some, but no sports drink can meet the needs of everyone. What is too much for one athlete is too little for another.
For every 100mg of sodium lost in "normal" sweat, we also lose approximately 78mg of chloride, 22mg of potassium, 2mg of calcium, and 2mg of magnesium. Ipso facto, electrolytes must be replaced in that order assuming the athlete begins with adequate levels of each electrolyte, and the athlete follows a typical pattern of sweat composition (which they very well may not). Therein lies the crux of the problem. Our diets, even if we’re health-conscious, are more susceptible to high sodium, high chloride, low potassium, low calcium, and low magnesium. All the while, most sports drinks are hyperfocused on just a few present in sweat.
Therefore, while we do not lose much potassium, calcium, or magnesium in sweat relative to sodium or chloride, we are likely already missing out on the benefits of consuming these minerals in adequate amounts from out diet! This is one of the reasons SustainElite contains all 5 minerals. An athlete can’t perform at their best if only consuming the minimum variety (NaCl) of essential nutrients, and yes! Minerals are essential nutrients! The funny part is we’re likely already eating enough salt to accommodate needs during exercise, and do not need a salt supplement for most activities (less than 2-3 hours), yet these are the only ones found in sports drinks. In reality, the drinks would be better suited with any of the other minerals unless needed for a lengthy event, in which case the athlete would need a salt supplement anyway.
Electrolytes for Endurance Athletes
Sodium, chloride, and to a lesser, but notable, extent, potassium are lost in sweat and should be a consideration for athletes to replace during exercise. The length of the exercise bout and sweat “saltiness” of the athlete will be the primary determinants regarding the necessity for electrolyte replacement. As these situations are specific, it is unlikely that a high-salt sports drink is necessary for most athletic endeavors. High-salt sports drinks may even exacerbate common pitfalls of modern, higher-salt diets. Ironically, the electrolytes that are often missing from sports drinks are the ones athletes may need the most. They are just omitted because they are not concentrated in sweat. All in all, a sports drinks primary purpose is to replace carbohydrate. The bottom line on electrolytes: athletes need all of them (!), not just salt, which you only need if you are a salty sweater and/or participating in a long event, and endurance performance can be enhanced when paying attention to other macrominerals (calcium, potassium, and magnesium).
References
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