Solved by a verified expert:Like humans, birds have fast twitch and slow twitch fibers. Flying requires bursts of energy and rapid movement. What type of muscle fibers are most likely used when chickens fly? Fast twitch, because they produce small amounts of energy quickly Slow twitch, because they produce small amounts of energy quickly Slow twitch, because they can contract for long periods of time without fatiguing Fast twitch, because they produce excess ATP