Both HIIT and Zone 2 training can increase mitochondrial biogenesis in skeletal muscle, with HIIT inducing it more rapidly.

“again both high-intensity interval training Zone 2 training also moderate intensity training can increase mitochondrial biogenesis in skeletal muscle hit does it more rapidly”

“and to get that metabolic flexibility it sounds like you know you don't necessarily have to be just a zone two trainer like you can do high intensity training again you're increasing your mitochondrial density there's a lot different ways to get there uh in terms of aerobic exercise it doesn't have to necessarily just be zone two”

“high-intensity interval training be being really time efficient and having many of the same benefits as even like a zone two type of training with respect to mitochondrial benefits cardiorespiratory benefits um if not even better if the same volume of exercis is performed in other words if you're doing 30 minutes of zone two and then a 30 minute high-intensity AAL training workout that you're going to have even more improvements in cardiorespiratory Fitness than you would Zone to you can have better improvements in mitochondrial density for example than you would”