Type IIa muscle fibers have lower mitochondrial function and density compared to Type I fibers because they can oxidize glucose in the cytosol, allowing for faster ATP production and lactate generation.

“Type two muscle fibers, especially the first type of muscle fibers, type two, the type two A's, they have lower mitochondrial function because... Lower mitochondrial function or density? Sorry, density. I'm sorry. Because they don't necessarily need to oxidize glucose in the mitochondria. They can do it in the cytosol of the cell and therefore produce lactate, but they can produce ATP fast. So those muscle fibers didn't contain as much mitochondria.”