Which of the following best describes the term 'flexion and extension'?

The term 'flexion and extension' specifically refers to the movements that involve bending and straightening of a limb. Flexion occurs when the angle between two body segments decreases, such as bending the elbow or knee, while extension is the opposite action where the angle increases, resulting in a straightened limb. In the context of physical movement such as in sports or exercise, understanding these fundamental actions is essential, especially as they relate to performance and body mechanics in activities like a golf swing.

The other options pertain to different aspects of movement that, while relevant to athletic performance, do not accurately define flexion and extension. For instance, rotating the hips during a swing involves movements in a different plane and is more associated with rotation rather than straightening or bending limbs. Shifting weight back and forth relates to balance and weight transfer, which are key to generating power and stability, but again, this does not capture flexion and extension. Changing grip pressure on the club describes a manipulation of the hold rather than a physical movement of the limbs. Therefore, the option describing bending and straightening of a limb directly aligns with the definition of flexion and extension.