Login | November 10, 2025
A brief primer on mitochondria
PETE GLADDEN
Pete’s World
Published: November 10, 2025
Over the years we’ve heard more and more about mitochondria's vital role in athletic endeavors.
But I think to appreciate how truly important mitochondria are, we really need to take a closer look at these mysterious little biological machines.
Thus, let’s explore two simple questions: What exactly is mitochondria and why in the heck are they so darned important to us when it comes to fitness?
So we’ll start the discussion by taking a seat in the Pete’s World wayback machine and venture back to the days of Biology 101.
In that freshman level class we remember that mitochondria are incredibly small peanut shaped organelles that inhabit human cells, and they’re roughly two microns (one micron is one-millionth of a meter) in length with a diameter of roughly one micron.
Heck, these little buggers are so small that within each human cell there can be as many as 1,000 to 10,000 of them.
We also remember that mitochondria are involved in a host of biological processes, not the least of which is energy production.
But mitochondria also play a big role in metabolism, cell death and in inflammatory processes.
So these organelles shouldn’t be thought of as strictly sports specific operators - they’re crucial to a myriad of bodily functions that reside outside the realm of sport and fitness.
Now returning back to the present, where we get back to the topic of mitochondria and sports performance, well, the important thing to know about these little guys is that they’re responsible for the production of energy substrates such as ATP.
And mitochondria produce this ATP via the metabolism of more complex molecules such as carbohydrates, fats and amino acids, all in conjunction with the use of oxygen as a fuel source to carry out said processes.
So mitochondria are absolutely crucial for our ability to take in food stuffs and convert those foods to usable energy within our cells - energy that can power us through any host of exercises and physical activities.
Now what most people don’t know about mitochondria is the fact that not all mitochondria are created equal.
Nope.
Fact is that they can come in different sizes, differing quantities and different functional qualities, all of which is determined by both our genetics and the their reactions to metabolic stresses - their reaction to repetitive physical exertions for example.
What’s more, mitochondria are sensitive to other factors such as various aging processes.
So the cool thing about mitochondria and its relation to fitness is the fact that these organelles absolutely will change both in quantity and in functional quality based on the training stresses we impose upon our bodies.
So what does that mean?
Well, say that you’re doing a regular regime of cardiorespiratory endurance training.
Said training will increase the number of mitochondrial organelles within the muscle cells thus allowing for more energy production.
Then there’s the qualitative changes, where in this example the mitochondrial organelles morph into more aerobic energy producing mitochondria.
Now if we were talking predominantly about anaerobic training, well, then there would be more anaerobic energy producing mitochondria created.
Not only that, but training stresses can also cause some functional alterations of the mitochondria.
Here we’re talking about improvements in oxidative capacity, enhancements in their ability to utilize oxygen efficiently and improvements in their expression of antioxidant enzymes (being able to protect against oxidative stress).
But not only does training have a big impact on mitochondria, it turns out that diet does to.
Indeed, because there’s a fat called triacylglycerol which is stored in muscle cells and close to mitochondria, and this fat can be metabolized by the mitochondria thus providing a pretty convenient energy source - a process is called Intramuscular triacylglycerolysis (IMTG).
Now the interesting thing here is that a lower-calorie dietary intake combined with exercise has been shown to play a role in elevating the levels of IMTG in a person.
In layman’s terms, this means that exercising folks whose diets are, let’s say adequate, are able to burn more of this intramuscular fat as an energy source.
Whereas folks whose diets are too calorie dense and/or sedentary, well, these people tend to build up higher levels of this intramuscular fat in their muscle tissue.
As you can see, optimizing the quantity and quality our mitochondria pays off in the way of improved endurance, better recovery, greater sporting performances and better fat burning abilities.
And these are just a few of the reasons why mitochondria are getting all those kudos.