What is the difference between muscular contraction and extension

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Explanation:

Isotonic contraction vs isometric contraction

Isotonic contractions generate force by changing the length of the muscle and can be concentric contractions or eccentric contractions. A concentric contraction causes muscles to shorten, thereby generating force. ... Isometric contractions generate force without changing the length of the muscle.

the last statement is correct i.e.

when your heart is not pumping enough blood around your body because your heart is severely failing, you may need an artificial heart. an artificial heart is a mechanical device, about the size of an orange, that is connected to your heart or implanted in your chest to or replace a failing heart.