TASC Sport Science 3 Practice Test

The key idea is how muscle fibers balance speed of contraction with how they generate energy. Type I fibers are slow to contract (their myosin ATPase activity is low) and rely predominantly on oxidative metabolism. They have many mitochondria, dense capillary networks, and high myoglobin, so they use oxygen to burn fats and glucose efficiently for ATP over long periods. That combination produces steady, enduring force with little fatigue, which is why these fibers are described as slow-twitch and fatigue resistant.

So describing them as slow-twitch, highly oxidative, and fatigue resistant accurately reflects both their slower contraction speed and their oxidative energy system. The other statements conflict with the fundamental traits of Type I fibers: they are not fast-twitch and not primarily glycolytic, and while some Type II fibers can be oxidative, they are characteristically fast-twitch and more prone to fatigue.