Which part of a muscle twitch occurs when the sarcomere distance is decreasing?

Question

Quizplus · Accepted Answer

The contraction period is when the sarcomere distance is decreasing as the actin and myosin filaments slide past each other, causing the muscle fiber to shorten and generate force. The latent period is the brief delay between the stimulus and the start of the contraction, during which the action potential spreads along the sarcolemma and calcium ions are released from the sarcoplasmic reticulum. The relaxation period occurs when the sarcomere distance is increasing again as the muscle fiber returns to its resting length and tension decreases. The refractory period is the time during which the muscle fiber cannot be stimulated again, due to the closure of voltage-gated ion channels. There is no such thing as an expansion period in muscle twitch.

Which Part of a Muscle Twitch Occurs When the Sarcomere