There are, as you already know, two main categories of fibbers in the skeletal
muscles of our bodies. The first type is known as slow twitch fibbers (or slow
oxidative fibbers, or red fibbers, or Type I fibbers) and the second type is
known as fast twitch fibbers (or white fibbers, or Type II fibbers). These two
types distinguish one from another on how fast they can contract. Another important
difference between them is in their capacity for endurance and power work.
Slow twitch fibbers have more endurance because they have a greater
capacity for aerobic metabolism. They have more myoglobin (the substance that
transports oxygen across the muscle cell), more aerobic enzymes that catalyze
the release of energy during aerobic metabolism, and more mitochondria (the
protein structures within muscle cells where aerobic metabolism occurs).
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