Magnesium: A Critical but Often Forgotten Electrolyte

Thursday, April 2, 2015 | By Todd Parker
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Magnesium: A Critical but Often Forgotten Electrolyte

The subject of electrolytes is a common one amongst endurance athletes. A majority of the focus has been sodium, calcium, and potassium, which which are certainly important. Unfortunately, magnesium is often overlooked. This critical electrolyte plays a key role in many functions of your body and is crucial to your performance.

The Importance of Magnesium

Electrolytes are ionized minerals that conduct electrical impulses and action potentials (e.g. contraction of a muscle), and are present throughout the human body. Simply put, the balance of the electrolytes is critical for normal function of cells and organs. Magnesium plays a critical role for extended bouts of muscular contractions and cramp prevention– just as much as the other three. Most people do not realize that magnesium plays an important role in calcium and oxygen transport throughout the cells of the human body. In fact, more than 300 nerve impulses and enzymatic reactions require magnesium as a co-factor. Besides calcium and oxygen transport, magnesium can directly affect sodium and potassium inter-cellular transport throughout cells as well. Longer and more intense exercise can deplete magnesium levels. Magnesium is excreted primarily through sweat and urine, therefore, cold fluids (empty out of the gut faster) are the preferred choice for replenishment during exercise.

Regardless of the type of sport or exercise, muscular contractions could not consistently occur without magnesium’s presence. Through aerobic and anaerobic metabolism- glycolysis occurs, in short, oxygen is delivered and utilized via magnesium. Therefore, O2 delivery to working musculature and energy production in the form of adenosine triphosphate (ATP) (the source for all energy production) would not happen without magnesium presence.

Causes of Imbalances

Magnesium imbalances may often be caused by things such as diuretics (e.g. caffeine), alcohol consumption, sweat loss, and both high intensity and high volume endurance exercise. Therefore, if you’re one who monitors your nutrition and electrolytes, and you’ve ruled out sodium, potassium, and calcium, look to magnesium intake as your possible cramping or contractile issue culprit.

For athletes, especially those training and racing in endurance sports, magnesium deficiency indicators may be one or more of the following:

  • Abnormal muscular weakness
  • Muscular cramping and locking
  • Muscular spasms
  • Impaired glucose breakdown (for ATP/energy production)
  • Inability to sustain exercise intensity for extended periods
  • Irregular heartbeat (e.g. elevated performance heart rate)
  • Disorientation and confusion

Conversely, excess magnesium is filtered by the kidneys; however, if overly excessive, kidney function is adversely affected. When this occurs, just as with deficiency, side effects may surface in the form of muscular spasms, and as I call it, muscular “locking”. Through proper monitoring, athletes can often supplement with 300-900 milligrams (mg) per day without contraindications. Larger dosages as in 700-900mg, should be broken up into 2 to 3 doses throughout the day with food. Female athletes should supplement at the lower end of this range, and don’t normally require any dosage above 300-400 mg. If oxygen uptake increases are a result, no matter how minor, this could, for example, improve a cyclists sustained power output. At approximately 5,500 revolutions per hour, such impacts may facilitate improved performances over normal homeostatic processes.

Good Sources

Magnesium is found in unrefined whole grain breads and cereals, as well as green leafy vegetables, lentils, peas, beans, nuts, and seeds. Meat, fish, fruit, dairy products, and processed foods are poor sources for magnesium.

In summary, endurance athletes should look for beverages that not only have calcium, potassium, and sodium, but ones with magnesium as well. If you’re cramping during longer training sessions or races, and have ensured that the other three are being replenished, then there’s a good chance what you’re experiencing is attributable to low magnesium levels.  

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