Mitochondria are the best friends you never knew you had. These little fellas, who evolved as symbiotic bacteria, live inside your muscles and produce ATP (the fuel our body run’s on) from fats and carbohydrates to keep us working. Mitochondria use oxidation for this process; hence they need a steady supply of oxygen and work aerobically.
The best thing about these little critters is that you can grow your number by aerobic training. Both high intensity and low intensity aerobic work has been shown to increase levels of Mitochondria.
Two metabolic effects of a high number of mitochondrial enzymes are:
1) Oxidize fat at a higher rate (thus sparing muscle glycogen and blood glucose)
2) A decreased lactate production during exercise.
Both these effects will improve aerobic performance.
Mitochondrial biogenesis takes weeks, as can be seen in the graph in Fig 1. Notice that once you have built up your own army of mitochondria they will decline if you stop training back to base levels, however thankfully this also takes weeks. So building those levels up will take a good solid block of 8 to 10 weeks of consistent aerobic work.
Dudley et al. (1982).
Another interesting bit of research by was that shorter high intensity runs drove mitochondrial levels up faster than long steady runs. So there is a strong argument here for performing intense shorter training to boost mitochondria biogenesis.
The take home from here is that mitochondria are an important part of your own physiology and increasing their numbers will make you a better athlete. What’s more the more you train the better those mitochondria will become at producing energy.
Studies have shown interval type training to boost mitochondria numbers higher and faster than long steady state training. However both types of training will eventually hit a genetic ceiling. So don’t take this as a green light to just do interval training. You still need to be performing most of your training in those easy aerobic zones for a multitude of reasons.
Another interesting point involves the results from a study by Western et al. (1999). The researchers of this study looked at a group of similar elite African runners and European runners. The African runners all showed markers in samples that pointed to higher mitochondrial levels, and the African runners performed better on time to exhaustion test. Now this might be non significant, and other factors could be at play, but it is an interesting study and food for thought.
Keep training smart,