Write 1-2 paragraphs to explain how the muscle or muscle group would contract to create flexion and extension

Explanation:

A volunteer muscle works generally across a joint. It is attached by strong cords called as tendons to both bones. Usually just one bone moves when muscles contract. Flexion and extension are usually body forward and backward movements, such as head nodding. Flexion: decreasing angle (bending) between two bones. Extension: to increase the angle between two bones (to straighten a curve).

"Reverse motions" require antagonistic pairs located on opposite sides of a joint or bone that include pairs of flexor-extensors. Both consist of an extensor muscle, which will "open" the joint (increasing the angle between the two bones) and a flexor muscle, which will do the reverse by reducing the angle between two.