There are three types of muscles (skeletal, cardiac, and smooth) but four types of muscle contractions. Here they are along with examples of muscles used:
1. Concentric contractions are contractions that cause the muscle to shorten. The muscle's maximum is always greater than the force generated by the muscle. An example of a concentric contraction is performing a bicep curl using weights.
2. Eccentric contractions are actually muscle lengthening contractions. As the external load on the muscle rises, the muscle can't create any more force so it instead lengthens. These contractions are common in everyday activities like walking. An example of eccentric contractions are the quadriceps extending as the knees flex while walking.
3. Isometric contractions cause the muscle to be held constant instead of shortening or lengthening. An example of an isometric contraction is holding a box of books in front of your body. The biceps are isometrically contracting.
4. Passive stretch is also a muscle contraction where the muscle is being lengthened in a passive state. An example of passive stretch contraction is the hamstring pull that occurs while doing toe touches.