Stand sideways to a cable machine and hold the handle with the arm farthest from the pulley. Start with your arm slightly across your body and a soft bend in the elbow. Pull the handle outward and back in a wide arc while keeping your torso stable, focusing on squeezing your rear shoulder and upper back. Slowly return to the starting position with control and repeat before switching sides.
Log your cable one arm reverse fly sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.