Final answer:
It is false that all people have the same proportion of slow-twitch to fast-twitch muscle fibers; the distribution varies by individual and is influenced by genetics and training.
Step-by-step explanation:
False. All people do not have the same proportion of slow-twitch to fast-twitch muscle fibers. The proportion of these fibers can vary greatly among different individuals. Slow-twitch muscle fibers, also known as type I fibers, are more efficient at using oxygen to generate more fuel for continuous, extended muscle contractions over a long time. They are the ones that endurance athletes, like marathon runners, tend to have in abundance. On the other hand, fast-twitch fibers, or type II fibers, are better at generating short bursts of strength or speed than slow-twitch fibers and fatigue more quickly. They are predominant in sprinters and individuals who engage in high-intensity, explosive activities. Genetics play a significant role in determining the ratio of these muscle fibers in an individual's muscles, but training can also influence their distribution to a certain extent.