Sarcomere Structure in Muscle Relaxation: Thin & Thick Filaments

When a muscle is relaxed, the thick filaments are present in the center of the sarcomere, along with the thin filaments. The thin filaments are not restricted to the center of the sarcomere during muscle relaxation.

During muscle contraction, the thick and thin filaments slide past each other, causing the sarcomeres to shorten and the muscle to contract. When the muscle is relaxed, the thick and thin filaments are not actively sliding past each other, but they remain interdigitated within the sarcomere.