Set-up: Lie down flat on your back, with a single dumbbell. Retract your shoulder blades and brace your core. Lift the dumbbell with a strong, fully closed grip. Start with a light weight to be sure you can handle the instability and positioning.
Lift: Forming a tight brace in your core to stabilize against the weight on one side, lower the dumbbell in a straight line to your chest, keeping the elbow close to the body until it just slightly touches the floor. Reverse the movement quickly while making sure the dumbbell travels in a straight line back up.
Emphasis: Keep the shoulder blades together and do not allow your shoulder to roll forward during the movement. Press to your chest, not your face. Do not bend your wrist, there should be a straight line through your forearm up to your knuckles.
Repetitions: Perform all prescribed reps on one side, then on the other. This counts as one set.