One Arm Lying Dumbbell Reverse Fly Video Exercise Guide

1. Set up for the exercise by setting a pair of dumbbells near a flat bench. Depending on the length of your arms, you may need to elevate the bench using blocks or steps.
2. Grab the dumbbells and position yourself with your chest flat on the bench. Your feet can be straight out behind you or used for stability on the floor.
3. Your arms should be hanging below the bench - holding the dumbbells with a neutral grip (palms facing one another).  
4. Keep your head up and your eyes facing forward. This is the starting position.
5. Moving only at the shoulder, raise your left arm in a semi-circular motion out to your side until your arm is parallel to the floor. Keep a slight bend in your elbow throughout the movement.
6. Squeeze your shoulder blades together at the height of the movement and then begin slowly lowering the dumbbell back to the starting position.
7. Repeat for desired reps, and then repeat with your right arm.

Exercise Tips:

1. Practice good form with a light weight.
2. Squeeze your shoulder blades and pause for a moment at the top of the movement.
3. Do not let the dumbbells "hang" at the bottom of the movement, but keep the tension in your arms.
4. Focus on moving only at the shoulders. The rest of your body should be kept as still as possible and your arms should hold the same form throughout the movement.