Is bending an elbow voluntary or involuntary?

Bending an elbow is a voluntary movement.

Voluntary movements are those that are consciously controlled by the brain. For example, when you decide to pick up a cup of coffee, your brain sends signals to your arm muscles to contract and relax in a coordinated way, allowing you to move your arm and hand to grasp the cup.

Involuntary movements, on the other hand, are those that occur without conscious control. For example, the beating of your heart and the digestion of food are involuntary movements that are controlled by the autonomic nervous system.