Mitochondria are the powerhouse energy producers tucked away inside every cell. When you exercise, these tiny, but powerful, organelles, work hard to produce enough ATP to fuel muscle contractions. Beyond being energy producers, researchers now believe that mitochondria play a role in aging as well.
What we currently know about mitochondria and exercise is that endurance exercise increases the number of mitochondria inside muscle cells. As you know, your body has an amazing ability to adapt and this adaptation gives your cells the ability to make more ATP. What could be better when you’re doing long periods of exercise? More ATP-producing mitochondria help you sustain exercise longer.
That endurance exercise increases the number of mitochondria, a process called mitochondrial biogenesis, is well known. Now, a new study carried out by researchers at the University of Southern Denmark Faculty of Health Sciences suggests that exercise may change the QUALITY of your mitochondria as well.
Mitochondria Are Built for Energy Production
Would you believe mitochondria were probably once free-living bacteria that attached to cells and integrated themselves to form a cozy, symbiotic relationship? These energy producers even have their own source of DNA. If you were to look inside mitochondria, you’d see folds called cristae. These folds form a double membrane across which energy production (ATP) takes places.
This study shows that exercise may actually change the structure of the mitochondria inside your cells so that they’re more efficient. We know that endurance exercise increases the number of mitochondria you have within cells but this study suggests it changes the composition of the mitochondria as well. It all adds up to more and better mitochondria to make more energy to fuel exercise.
Specifically, what the researchers found is endurance athletes have mitochondria that generate 25% more energy compared to what a non-athlete’s mitochondria produce. That’s pretty remarkable if you think about it! To reach this conclusion, researchers looked at the muscle fibers of 15 elite athletes using a special microscope that allowed them to visualize even small changes inside muscle cells.
What’s not clear is whether these elite athletes had better quality mitochondria to begin with, or whether training caused them to change in quality. Based on their observations, they believe the upgraded mitochondria develop from exercise training rather than existing beforehand. It’s also not clear how long or hard you need to train to upgrade your own mitochondria.
What is clear is that endurance training causes a number of adaptations designed to help deliver oxygen to muscle tissue and to enhance ATP production. Some of these include:
· An increase in stroke volume of the heart, allowing it to pump more blood with each beat
· An increase in hemoglobin to pump more oxygen to tissues
· Increase in capillary density around muscle tissue
· Increase in the number of mitochondria inside muscle cells
The Importance of Healthy Mitochondria
It’s true that healthy, efficient mitochondria benefit aerobic exercise performance but scientists now suspect that mitochondrial health plays a role in aging as well. As you age, your aerobic capacity drops, partially because mitochondria become less efficient energy producers. As a result, your stamina and endurance decrease – but the implications go further than that.
Research has linked the age-related decline in mitochondrial productivity with insulin resistance. As mitochondria become “tired” or damaged, cells become less sensitive to the effects of insulin. This places extra pressure on the pancreas to produce more insulin. Depending upon how much reserve your pancreas has, it can pump out extra insulin for a while but will eventually fatigue. That’s when blood sugars rise and you cross over into type 2 diabetes. Not surprisingly, insulin resistance is associated with an increased risk of type 2 diabetes, heart disease, and, possibly, some forms of cancer. So, healthy mitochondria affect your health independent of exercise performance.
Exercise and Mitochondrial Biogenesis
One of the adaptations to endurance exercise is a bump up in the number of mitochondria and, as this new study shows, the mitochondrial structure may change as well. Your body’s pretty smart. It knows that extra mitochondria will increase oxygen delivery and make future exercise sessions more sustainable. More efficient mitochondria will be beneficial as well. Endurance exercise is that which you do for long periods of time at a steady pace – but is it the only type of workout that boosts mitochondrial biogenesis?
If the thought of doing an hour or more of monotonous cardio to nurture your mitochondria brings tears to your eyes, you have an alternative. Studies show that high-intensity interval training upregulates genes that code for new mitochondria. The beauty of HIIT training is it takes less time and is less monotonous. It also boosts aerobic AND anaerobic fitness. In fact, some studies show that high-intensity exercise is MORE beneficial for heart health than moderate-intensity exercise, like brisk walking or jogging.
Whichever type of training you do to boost the health of your mitochondria, be consistent about it. One study showed training can boost the number of mitochondria in muscle cells by as much as 50% over a 6 to 8-week period. The downside is, you lose those extra mitochondria quickly after you stop training. In fact, you lose about half your mitochondrial gains after two weeks of being sedentary. Staying physically active consistently is one of the best ways to maximize the mitochondria within muscle cells.
The Bottom Line
Aerobic exercise, both endurance and high-intensity interval training, boosts the number of mitochondria inside muscle cells but they may also change the structure of these ATP producers as well, making each one more efficient. The extra ATP they produce is what gives you stamina. Plus, healthy mitochondria are linked with successful aging as well. Right now, the best thing you can do is give those mitochondria a reason to proliferate and become more efficient and you do that through exercise.
Eurekalert Science News. “New Research on the Muscles of Elite Athletes: When Quality is Better Than Quantity”
Med Sci Sports Exerc. 2003 Jan;35(1):95-104.
Gerontol A Biol Sci Med Sci. 2006 Jun; 61(6): 534–540.
Karolinska Institutet, Stockholm, Sweden. “The Effect of Different Exercise Regimens on Mitochondrial Biogenesis and Performance”
Juvenon Health Journal volume 7 number 10 July 2014. “Endurance Exercise: Keeping the Mitochondria Furnaces Burning”
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