In anatomical terms, what does flexion refer to?

Flexion refers to the action of decreasing the angle between adjacent bones, typically occurring at a joint. This movement brings the two bones closer together, such as bending the elbow or knee. For example, when you flex your arm at the elbow, the angle formed between the forearm and the upper arm decreases. This concept is fundamental in understanding joint movements and is applicable in various exercises and functional movements in both everyday activities and athletic performance.

The other options describe different types of movements: increasing the angle corresponds to extension; rotational movement pertains to actions like twisting; and extension specifically involves straightening a limb. Each of these terms highlights a unique aspect of joint movement, but flexion is specifically characterized by the reduction of the angle between two bones.