Q.Bending the elbow during a biceps curl, which decreases the angle between the two bones, is an example of:

Flexion: Bending at a Joint

Imagine your arm hanging straight down. Now lift your forearm toward your shoulder, making a "muscle" pose. That motion — the one that makes your biceps bulge — is flexion. It's the simplest, most intuitive movement you perform dozens of times a day: bending.

The Intuition

Flexion is bending. When you bend your elbow, your knee, your neck forward, or curl your fingers into a fist, you are performing flexion. The key visual is that the angle between two body parts decreases. Your forearm and upper arm start nearly straight (180°), and as you curl your hand toward your shoulder, that angle shrinks — to 90°, then smaller.

The Precise Anatomical Definition

Flexion is a movement that decreases the angle between two body parts at a joint. It occurs in the sagittal plane (the vertical plane that splits the body into left and right halves) around a transverse axis (an imaginary line running left-to-right through the joint).

Here is the critical detail: the movement is anterior (forward) for most joints, but posterior (backward) for the knee and toes.

The Opposite: Extension …