"To move the arm" means to change the position or direction of your arm.
Sentences with «to move the arm»
Along with the basic fighting mechanics, an optional feature with holding both joy cons in your hands, allows you to perform certain super moves by moving your arms in a certain way. (dailyjoystickpodcast.com)
Lower the dumbbells by bending your elbows, but don't move your arms. (fitwirr.com)
As well as moving your arms up and down you also need to push forward at the same time to keep your feet in place. (unique-bodyweight-exercises.com)