He throws a phenomenal ball and has a nice loose arm swing.

She saw his arm swing, and caught the glitter of steel.

In other words a subject needs less reaction moment applied by the ground surface when there is arm swing.

Less dependence on the friction force, hence environment, is a possible outcome of arm swing.

Racewalkers are also utilizing the arm swing for its energy efficiency.

Paula saw his arm swing hard, down, up, then with a cross slash.

When used in this way, an exaggerated arm swing is often used.

Somebody had swung for the fire escape and reached it, whether by an arm swing or with the aid of a rope.

Contact the ball with the cupped fingers and a long arm swing.

In short, the athlete would have a hard time controlling the rotation of their trunk without arm swing.