In Zone 2 exercise, fat and glucose are oxidized within mitochondria with a low glycolytic flux that is also oxidized, rather than being converted to lactate.

“And in the moment you tap into the fast-twitch muscle fibers is because the ATP demand that you need cannot be covered by fat. And you need to switch to a different fuel. And that's where we see a big drop in fat oxidation. And we see an increase also in glucose oxidation. And that's when we start seeing also an increase in lactate as well.”

“zone two being defined as this area where you have the maximum efficiency of the mitochondria so you're able to keep lactate systemically below 2 millimole and just barely keep it there right so your sort of maximum utilization of glucose and fatty acid that is mitochondrial without undergoing non-ox”

“so you know we talk about it in zones right so there we think zone two is how we describe it and this is we we Define it by lactate metabolism so zone two is that all day Pace lactate has to be below two Millar you have to be a this is a pace you should be able to hold all day from a metabolic standpoint you probably can't hold it all day from a muscular and structural standpoint but metabolically you should be able to hold this pace all day”

“that happens at that uh in those muscle fiber types those muscle fiber types and the mandra of those F fiber types also develop um these Transporters which are MCT ones which are the ones is that transport lactate inside the cell and inside mitochondria”

“this is where you burn uh both the FX The Fat inside am country as well as the glucose inide the mandri there's not a very high glycolytic flux that um it's going to be transformed into pyate and reduced to lactate but that flux still is oxidized inside mitochondria”

“zone two is how we describe it and this is we we Define it by lactate metabolism so zone two is that all day Pace lactate has to be below 2 Millar you have to be a this is a pace you should be able to hold all day from a metabolic standpoint you probably can't hold it all day from a muscular and structural standpoint but metabolically you should be able to hold this pace all day”

“what we're really kind of looking for is the harnessing of mitochondrial efficiency and to do that you 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's there still there's still value in that but not for what we're talking about”

“those F fiber types also develop U these Transporters which mctt ones which are the ones is the that transport lactate inside the cell and in mitochondria so when you stimulate that training Zone you stimulate all these Energy Systems and the components that come with them”

“so Zone 2 is my highest work my highest power output where my lactate stays below 2 m so this is very sustainable from an RP perspective you know it's it's it's RP 6 to7 I can talk but I'm not comfortable talking but I can talk it's definitely below my 1hour functional threshold power um but it's more challenging than that 200 Watts riding around in circles having fun trying to just purely Focus on position um and I do use my lactate I do check my lactate constantly to make sure that I'm really hitting that spot”

“So, if you are training in zone 2, while you're not getting as much adaptation as you're getting at zone 5, uh you're still applying a strong enough training stimulus to activate muscle uh sorry, both fuel systems, right? So, you're you know, you're not maximal, but you're near maximal for fat oxidation. You have some glycolysis. You have lactate shuttle but you don't have the wear and tear of the acidity and the fatigue that comes when lactate production completely overwhelms clearance uh systemically.”

“and then there are others who would argue or say you know I think there's decent evidence support that something like zone two training also improves your lactate clearance capacity”