Sit at a cable machine with a straight or V-bar attached overhead. Grasp the bar with an underhand (palms facing you) grip and engage your core. Pull the bar down toward your chest by driving your elbows down and back, squeezing your shoulder blades together at the bottom of the movement. Slowly allow the bar to rise back up with control, maintaining tension throughout the motion.
Log your cable reverse grip pulldown sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.