Tonic muscles have a high proportion of what type of fibers?

Tonic muscles are characterized by their role in maintaining posture and stability, which requires endurance and sustained contractions over extended periods. As such, they typically possess a high proportion of slow twitch fibers, also known as Type I fibers. These fibers are more efficient at using oxygen for sustained activity, making them ideal for activities that require endurance, such as standing or holding positions for prolonged periods. They are also more resistant to fatigue than fast twitch fibers. This characteristic contributes to the muscle's primary function of stabilizing the body and maintaining posture over time, rather than producing rapid, powerful movements associated with fast twitch fibers.