Type 2x muscle fibers primarily rely on glycolysis and may lack surrounding mitochondria, unlike type 1 fibers which have abundant mitochondria and readily access glucose and fatty acids oxidatively.

“so the ones that are pure type one have generally more mitochondria and they are less fatigable they don't produces much force um relative to well they do relative to size but uh they're slower and they do that as you move to 2A and to 2x they become faster but they become more fatigable because they're more relying upon on um glycolysis in carbohydrate metabolism”