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The Power and Importance of Mitochondria

BY Molly Breslin

Mitochondria play a fundamental role in your performance as an endurance athlete. Molly Breslin breaks down what mitochondria is, why it is important, and how you can increase it.

Many of you may wonder what mitochondria are and why you should care about them. As an endurance athlete, the microscopic entities (organelles) located inside your muscle cells known as mitochondria are critical to your training and racing success. It doesn’t matter if you are a beginner or a pro athlete; the proper care and feeding of your mitochondria is crucial. Let’s begin with what a mitochondrion (singular) is.

Mitochondria Explained

Mitochondria are affectionately referred to in almost every academic physiology textbook as the powerhouses of the cell. For our purposes we are going to focus on the muscle cells of the skeletal and cardiac (heart) systems but mitochondria populate many other cells of the human body. A mitochondrion is 0.5 to 1.0 microns in size; that represents 0.0000195 to 0.000039 of an inch. To put this in perspective, the head of pin is 2 millimeters in diameter. A mitochondria is merely a 4,000th to 2,000th the size of the head of a pin. Up to one-third of the volume of your skeletal or cardiac muscle cell is taken up by mitochondria. Incredulous that something so miniscule can put you on the podium? Here is a distilled version of the cellular physiology behind the magic and how to manage it to your advantage.

How Mitochondria Function to Help Produce Energy

As athletes, we all know about oxygen and carbohydrates (sugar). The mitochondria take both of these ingredients, also called substrates, and use them to produce the energy (product) that makes your heartbeat and your muscles perform. Glucose (the form of sugar found in our blood stream) is repackaged inside the complex internal structure of the mitochondria into two key components: pyruvate and Nicotinic Adenine Dinucleotide (NADH). These two chemicals are now transported into the central part of the organelle where, in the presence of oxygen (this is of primary importance), they are used to produce ATP (adenosine triphosphate). ATP is a nifty little chemical that is essentially the energy currency (think money, not electricity) of the cell. This all happens via the Krebs Cycle.

How ATP Functions

Now that I have piqued your interest and you are starting to wonder exactly how that ATP helps you turn the pedals and stride the miles, let’s talk about what ATP actually does. Inside your muscle cell there are tiny little fibrils (essentially filaments of protein) called Actin and Myosin. The complex physical interaction of these fibrils will be the topic of another article, but in the meantime it’s just important to understand that ATP binds to the myosin fibril and causes the muscle to contract (be it skeletal or cardiac). To give you an idea of how important ATP is, Rigor mortis ensues when your body is no longer able to supply ATP to your working muscle cells. If you have ever bonked in a race it was a result of your muscle cells being depleted of glucose, oxygen, and ATP.

Production of energy for your working muscles is an extremely complex biochemical recipe, but it can all be boiled down to the simple ingredients of sugar, oxygen, and calcium. Sugar supplies the basic building blocks (remember pyruvate and NADH) that the mitochondria use to produce ATP in the presence of oxygen (the whole process is called oxidative phosphorylation). Calcium is essential to transformation of glucose into the pyruvate and NADH as well as the interaction of the myofibrils myosin and actin mentioned above.

The Importance of Oxygen

This process is completely dependent on the presence of oxygen as it represents aerobic respiration inside your working muscle cells. Hopefully, this gets started thinking about your heart rate monitor. Your working muscles use glucose to produce ATP at a rate 13 times higher in the presence of oxygen than when oxygen is not readily available. If your heart rate monitor alarm is screaming because you’re exceeding your lactate threshold it won’t be long before you bonk.

Now here is the best part – exercise actually results in mitochondrial proliferation within muscle cells. What this means is that by exercising, you are essentially asking your body to provide you with more energy and it responds by revving up its own cellular machinery.  The Australian Society for Biochemistry and Molecular Biology published a fascinating article that explains this in more detail if you’re looking for an in depth publication on the subject.

How Can You Help Mitochondria Production

Your cellular biochemistry cannot do all the work on it’s own; it needs you to be it’s teammate in the process. How can you help your physiology to perform at it’s best? Here of some simple things you can do to optimize this process and make the best of your training and have a great race performance:

Train Smart 

Overtraining and training without appropriate recovery damages muscles cells and the intracellular machinery. Create training programs and hire a coach if you are able.

Stay Hydrated

Optimal cellular function is dependent on the right balance of water so that transport of substances occurs readily. Dehydration leads to “gunking” up of the system. Be sure to stay hydrated throughout the day and in training.


Feed your mitochondria a steady diet of available sugar. This means consuming carbohydrates in a manner that gives your cells readily available fuel (glucose) for training and racing and well as eating a well-balanced diet and choosing high-quality recovery snacks to boost your glycogen reserves. Additionally, muscles and mitochondria need protein to proliferate. Make sure your protein intake is adequate and high quality.

Constant Oxygen Supply

Mitochondria cannot function in an anaerobic environment. Training in zone 2 is the best way to develop more mitochondria. Know your maximum heart rate and lactate threshold and use your heart monitor to keep that oxygen flowing freely to your cells.


As we discussed, calcium is integral to the biochemical process, but calcium does not exist and function in isolation. Calcium’s availability and function is inextricably tied to the levels of other electrolytes like potassium and magnesium as well as the pH of the blood. Make sure you are ingesting a balanced mix of electrolytes when training and racing.

About Molly Breslin

Molly is the founder, owner and lead coach of 22Tri.  She holds professional certifications in Sports Nutrition and Nutrition for Optimal Health and Wellness from San Diego State University. As an advanced practice nurse and an avid and accomplished multisport athlete, Molly recognizes that nutrition is the often-overlooked piece of an athlete’s training plan. Her mantra is: “Good nutrition and a sound nutritional plan will immeasurably enhance an athlete’s training and racing performance.” Molly works with athletes from the beginner to the elite level in triathlon, running, xc and randonee skiing, road cycling, and mountain biking. She writes for Training Peaks, USA Triathlon, CapoVelo and Active.com and runs seminars on sports nutrition and training clinics for running, swimming, cycling, and triathlon. Molly is also credentialed as a Health and Wellness Coach through Harvard University School of Medicine and American College of Sports Medicine affiliate Wellcoaches, and is a a certified Exercise Is Medicine professional through the American College of Sports Medicine.