Final answer:
The term 'intermediate fiber' refers to fast-twitch, oxidative muscle fibers, often termed fast oxidative (FO) fibers, which are used for activities that are more intense than posture but less intense than sprinting.
Step-by-step explanation:
Intermediate fibers refer to skeletal muscle fibers that display properties between those of fast-twitch and slow-twitch fibers. These fibers are also known as fast oxidative (FO) fibers. FO fibers, which are primarily used for activities like walking that require more energy than maintaining posture but less than explosive movements like sprinting, can produce ATP rapidly through aerobic pathways. They are packed with mitochondria, enabling them to be more resistant to fatigue. Unlike the red-colored slow-twitch fibers that have high myoglobin content, FO fibers have less myoglobin, giving them a lighter color. Among the options given: A. fast-twitch, glycolytic fiber; B. fast-twitch, oxidative fiber; C. slow-twitch, glycolytic fiber; and D. slow-twitch, oxidative fiber, the correct answer is B. a fast-twitch, oxidative fiber.
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