Zone 2 exercise is the intensity at which mitochondria produce the maximum amount of ATP under purely aerobic conditions, primarily by recruiting type 1 muscle fibers.

“and slow twitch type one fibers you think about endurance activity you think about high mitochondrial density all of which is important we've seen that over time if you are inactive one of the Hallmarks of Aging is a decrease in mitochondrial function therefore doing some kind of stimulation of Zone 2 training can potentially be beneficial”

“zone two is the place at which your mitochondria are producing the maximum amount unsaturated under purely aerobic conditions of ATP. Is that fair? Yeah, I would say that too. And that's where you're still recruiting those type 1 muscle fibers.”

“Now, of course you talk about the need for a treatment here, but you already know, you've already discovered arguably the single best treatment imaginable for this, which is more zone two. How do you increase mitochondrial function? You train at the maximum level of mitochondrial output, correct? That's my hypothesis. And that's what I have been seeing for 25 years working with elite athletes, that this is the exercise intensity of what I see the biggest improvement in fat burning and the biggest improvement in lactate clearance capacity. Therefore, that means that mitochondria is where you see the biggest improvement.”

“there's certainly some evidence that this uh increases our mitochondria's ability to combat reactive oxygen species and all sorts of other damaging processes involved in inflammation”

“zone two is basically the highest level of exertion that is effectively pure mitochondrial oxidative phosphorylation before you start to net accumulate lactate”

“it is the exercise intensity at the one you are stressing mitochondria and oxidative capacity to the most uh this is where you're recruiting mainly type one muscle fibers this is where you are mobilizing the highest amount of fat”

“looking at just sort of mitochondrial function mitochondrial health density and then looking at sort of the the sort of neurotrophic factors that bdnf secretion that can come from this type of activity”

“so um zone two or Z2 right um I started using it like about 25 years ago um and I just have a very simple um name so to um it is from my um point of view it is the exercise intensity at the one you are stressing mitochondria and oxidative capacity to the most uh this is where you're recruiting mainly type one muscle fibers this is where you are mobilizing the highest amount of fat um both from lipolysis from MIT tissue as well from fat oxidation inside the MIT the mitochondria and this is also where um uh you stimulate all those uh energy that that b energetics which is um City phosphorilation this is where you burn both the F the fat inside M as well as the glucose inside the mandria there's not a very high glycolytic flux that um it's going to be transformed into pyate and reduce to lactate but that flux still is oxidized inside mitochondria and uh uh this is looking at from B energetic standpoint this is what I would consider the zone two”

“a way that people can think about this I would say is muscle fiber recruitment so low intensity is primarily slow twitch muscle Fiers is doing the majority of the work and specifically Zone 2 we're talking about where they're mostly oxidizing fat as much as possible kind of this moderate intensity we're starting to recruit some of those moderate threshold fibers we can talk about what that means but we're starting to recruit some of those those those faster twitch higher threshold muscle fibers and then higher intensity we're starting to really recruit all the muscle fibers and the highest intensity of muscle fibers”

“What you're really kind of looking for is the harnessing of mitochondrial efficiency. And to do that, you just you have to be able to push oxidative phosphorilation right to its limit before you trip into glycolysis. And you're just you're at the limit of that glycolysis being the dominant energy source. Whereas if you're on that ride, you're going into and out of glycolysis constantly. So it's not that you're so much in zone 2 for 45 minutes as that you passed through zone 2 for a sum total of 45 minutes which again that there still there's still value in that but not for what we're talking about.”

“but the key I think and one of the main benefits reported for Zone 2 is that you're improving your fat burning capacity not only during exercise but also your mitochondria's ability to oxidize fat as its energy source because that's the intensity at which the fat oxidation in the mandra is is maximal”

“If we're talking about mitochondrial biogenesis, you know, great zone 2 does in increase mitochondrial biogenesis, but you know, if you start to go a little more vigorous, you actually can get a stronger stimulus. And I know that's um what we're talking about here, vigorous includes zone 2, but I'm just saying generally speaking, um it the more it just gets back to this whole idea, right? The more intense the stimulus, the greater the adaptation to a degree.”