Potassium’s Role in Endurance Sport – Primer on Common Issues

This article is a continuation on our electrolyte discussion of the importance of electrolytes in endurance sports. In part one, we addressed the role of sodium and some common symptoms of either having too little or too much of it in our system. This article focuses on potassium which acts as a counterbalance to sodium. So while there is higher concentration of sodium within our cells rather than outside, the opposite is true for potassium as it prefers to exist outside the cells. Potassium and sodium work together to ensure the proper amount of fluids within and outside our cells. This is done via something called the Sodium Potassium Pumps (a little too advanced for us non Phd in Biology runners).

In this article we will focus on how to ensure you have enough potassium in your system and on some of the symptoms of being out of balance with regards to potassium.

Potassium importance in Endurance Sports

How do we get potassium into our bodies?

Just like most other electrolytes, potassium is obtained mostly via the food and drinks we consume. The most popular method is the legendary endurance fruit – the banana (read our comparison on bananas vs energy gels for a deep dive). There are a lot of other fruits and vegetables that have really high concentrations of potassium, but they are less likely to show up at a marathon or ultramarathon checkpoint. We eat or drink a substance, it goes through our stomach into the gut and gets absorbed into our blood stream. It’s the kidney’s role to filter the blood and thus regulate the amount of electrolytes, in this case potassium, in our system.

What happens if our body is low on potassium?

Every electrolyte in our body has a very specific range of concentration that is ideal for our system to function properly. For potassium, that number is 3.5-5 mEq/L, and if our body goes above or below that level we can get into trouble. Specifically when we fall below our desired range, we go into a condition called HypoKalemia. The causes of our potassium levels going to low range can be diuretics, steroid imbalance, too much insulin in our system, or simply not eating enough food with potassium in it. As far as the symptoms, the nurses who are getting ready for an exam on electrolytes have devised a mnemonic device to remember them – they call it the 7Ls of low potassium, None of them are ideal for peak performance during endurance races:

  • Lethargy (been there)
  • Low or shallow respiration (not a happy place for a runner)
  • Lethal cardiac dysrhythmias (scary stuff)
  • Lots of urine (been there and know some runners who must be really low on Potassium based on this symptom)
  • Leg cramps (been there and I know I’m not alone)
  • Limp muscles (ohh boy)
  • Low blood pressure & heart rate (never been in bad enough condition to have my blood pressure checked during a race)

Watch out for these conditions and make sure to take in plenty of potassium rich food to ensure you don’t fall victim to these unpleasant symptoms.

What happens if our body is high on potassium?

If your body’s potassium concentration is too high on the other hand, this condition is known as HyperKalemia. This condition is typically caused by muscle breakdown which leaks potassium into our blood, or by kidney’s not functioning correctly to help us release excess potassium into our urine. The symptoms are also not very pleasant, and the good nurses have also come up with a suitable acronym to help us remember them: M-U-R-D-E-R:

  • Muscle weakness (been there, but not sure if I can blame it on too much Potassium)
  • Urinary output
  • Respiratory failure (we really don’t mean to scare anyone with this blog piece)
  • Decreased cardiac contractility (sorry guys, I guess its too late about the not scaring runners)
  • Early muscle twitches (I’m pretty sure I’ve seen my muscles freak out after a long hard run)
  • Rhythm change in the heart

Obviously these are symptoms that don’t make for optimal physical performance.

In the next electrolyte article, we will touch on the remaining key electrolytes in our bodies – chloride, magnesium, phosphate, and calcium.