Grab hold of a suitable weight dumbbell and take position in a split stance. The leg on the same side as your lifting arm is back; the leg on the same side as your non-lifting arm is forward and you are placing the body weight on the front thigh. Setting the forearm on that thigh can help with balance. Your torso is at a 45 degree angle to the floor and you are bent only from the waist, not arching your back.
Hold the dumbbell in your lifting arm with a palm facing inward grip. That arm is at a 90 degree angle with the hinge point, the elbow, being pinned to your side. This is the starting position.
Commence the movement by extending at the elbows to kick the dumbbell backward. The upper arm should remain stationary and the movement comes only from the forearms. You should feel a the contraction through the triceps. Exhale through the movement.
When the arm is fully extended behind you, elbow remaining pinned to your side, reverse the movement by returning the arm back to the starting position without lifting your elbow, inhaling as you do.