I am not a chemist, nor have I taken a chemistry class since college, which wasn’t even in the past decade, nor the one before…nor, well, you get the point, so when I was recently asked to speak at the University of Regensburg to a group of high school (gymnasium) students interested in studying chemistry, my first reaction was, "What does ultra running have to do with chemistry?" Then I realised the answer is quite simple: Just about everything.

Looking back on my preparations for multi-day stage races, I’d spend hours determining just what my body needed to function under extreme circumstances because I knew that if my training had been adequate and my mental strength was in good form, then nutrition would be the key to optimising my performance and reaching the finish line. That said, not only do endurance sports and biological chemistry go hand-in-hand, but without a basic understanding of our own body’s chemistry, we runners wouldn’t get very far on our feet!

So for the chemistry students, I did some research and applied some of their jargon to the runner's lexicon and introduced myself to the endurance athlete's two best friends: Electrolytes and Amino Acids

Let’s start with electrolytes.

Electrolytes are chemical elements which, when mixed with water, conduct electricity and support specific bodily functions. The heart, muscle, and nerve cells use electrolytes to carry electrical impulses to other cells. They function to regulate nerve and muscle action, hydrate the body, balance blood pressure, and even help rebuild damaged tissue.

Periodic Table of the Elements: The chemistry student's bible

Electrolytes that are found in the human body include, but are not limited to:

Electrolytes are lost when we sweat and need to be replaced. A general electrolyte deficit can lead to cramps, dizziness, confusion, an increased heart rate, and nausea, which are (coincidentally?) some common complaints of runners during long-distance races.

There are many scientific studies about what the body needs during sport. Depending on many factors including length of exertion, air temperature, humidity, and individual factors, if and how much of an electrolyte supplementation is required varies widely. A general consensus is that an electrolyte supplement is not vital under exertion of less than 90 minutes. Thus, during a foot race of 10 km or shorter, we should not require more than water to maintain good hydration. But what if the race is longer? And it is sunny and HOT?

That’s when isotonic drinks come into play.

We are all familiar with the term ‘isotonic sports drinks’, but what does the term isotonic really mean?

An isotonic drink is a drink in which the ratio of nutrients to liquids corresponds to that of human blood, which means that the osmotic value has the same tonicity as human blood and can therefore be digested relatively quickly. Some isotonic drinks have been recommended for restocking levels of electrolytes during and after exercise to help restore lost sodium and potassium as well as to retain water.

As a comparison:

Hypertonic drinks typically contain high electrolyte content and consuming too much can lead to an excess, which results in similar side effects as a deficit. Excesses are typically filtered out of the body via the kidneys, but during a race we certainly don’t want any of our organs working on overload. They have enough to do already!

Most sports gels contain electrolytes but many also have a considerable amount of sugar (carbohydrates), which may or may not be desired. Another means of replacing sodium is by taking salt supplements which are readily available in tablet form specifically produced for athletes. Prior to running the 257-km Marathon des Sables across the Sahara Desert, all competitors are provided with a bag containing 200 salt tablets. We were required to take two tablets with each 1.5-liters of water that we drank and were reminded of this at each check-point by the doctors and staff because in that extreme environment a sodium deficit could quickly lead to dehydration and even death.

holly zimmermann marathon des sables endurance asics frontrunner
Marathon des Sables - Sahara Desert, Morocco

The message here is that during exertion of several hours or longer when we are sweating, our bodies will require an electrolyte replacement for optimal function and health, the amount of which varies upon the individual and the conditions.

Moving on to Amino Acids…

As opposed to electrolytes, amino acids are not chemical elements but chemical compounds. They are the building blocks of proteins in the human body and serve primarily to build up body tissue. Thus, for the athlete, they are important for recovery and regeneration. In a very long distance or multi-day stage race, an accelerated regeneration is essential to maintain (or minimise the reduction of) performance levels.

Of the 20 standard amino acids, nine are called essential amino acids because the human body cannot synthesize them from other compounds at the level needed for normal growth, so they must be obtained from food. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The following chart lists the nine essential types, their functions in the human body, and some food sources in which they are found.

holly zimmermann asics frontrunner running ultramarathon

Glutamine is another important amino acid but one that the human body naturally produces; although, intense physical exercise drains glutamine stores faster than the body can replenish them. When this occurs, the body breaks down muscles and becomes catabolic, and performance and recovery can be compromised. Glutamine supplementation has been shown to aid in recovery and recuperation in addition to boosting immune function. The best time to take a glutamine supplementation is right after a hard exercise session since glutamine stores in muscle can be depleted up to 40% after exhaustive exercise.

Thus, unless you are competing in a non-stop multi-day race, amino acids typically do not need to be supplemented during a race, but can be taken following the exertion to help with regeneration. Amino acid supplementations are widely available for athletes in the forms of tablets, gels, powders and drinks. During the Marathon des Sables I used them in tablet form after each stage, to which I credit my best performance of the week in terms of ranking occurring on the very last day of the race. In addition to being used in the evenings during multi-day stage races, they can also be helpful after difficult training sessions, a tough race, or during periods of intense training.

Again, I am not a chemist, a doctor nor a nutritionist. I am a passionate runner who is fanatical about being prepared for extreme events. Please do your own homework* on this topic when planning for your needs and use your training sessions as your own chemistry experiments.

*Dietary exposure to the non-standard amino acid BMAA has been linked to human neurodegenerative diseases, including ALS.

holly zimmermann asics frontrunner endurance running


Overtraining syndrome: a practical guide. Sports Health 2012; 4(2):128–138.

Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation. Nutrients. 2018; 10(11): 1564.

A critical review of the postulated role of the non-essential amino acid, β-N-methylamino-L-alanine, in neurodegenerative disease in humans. J Toxicol Environ Health B Crit Rev. 2017; 20(4): 1–47.

Wikipedia; MedicalNewsToday (online)

Image Credits:

Essential Amino Acids: Chromatos / Shutterstock

Aid station: Freepik

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Holly Zimmermann

Autorin von Alteglofsheim

Altersklasse: Seniorin

Meine Disziplinen
Yoga / Pilates Traillaufen Ultramarathon Ultratrail Marathon

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