The heart is made of a unique muscle type known as cardiac. The body also has voluntary muscles that are attached to the skeleton and some involuntary muscles that work the internal organs.
Muscles contract when they work. If a muscle contracts to create movement, it is called an isotonic contraction.
An isotonic contraction can be concentric, which is where the muscle shortens as the fibres contract or eccentric, where the fibres contract as the muscle lengthens.
When a muscle contracts with no resulting movement, it is an isometric contraction.