What are the positions of actin and myosin molecules in the sarcomere before and during the muscle contraction?
Schematically actin filaments attached perpendicularly to both sarcomere extremities (longitudinal sides) make contact with myosin filaments positioned in the middle of the sarcomere and in parallel to the actin filaments.
Before the contraction the sarcomeres are extended (relaxed) since the contact among actin and myosin filaments is only made by their extremities. During contraction actin filaments slide along the myosin filaments and the sarcomeres shorten.