The correct answer is "fast oxidative and slow oxidative fibers"
Myoglobin is the counterpart of hemoglobin in muscles. It is a single subunit protein that has a high oxygen affinity that "stores" oxygen until the muscles are in oxygen deficit wherein the myoglobin "let's go" of the stored oxygen. Both fast oxidative and slow oxidative fibers benefit from myoglobin as these fibers use more oxygen than other fibers.
