This is an isolation exercise movement for the forearms. Primary muscles used in this exercise are the forearms.
To perform reverse wrist curls grip the bar with your hands thumb width apart. While sitting on a bench rest your forearms flat on your legs with your wrists facing down hanging over the edge of your legs. Curl the bar upwards making sure you are using your wrists to move the weight and squeeze your forearms at the top of the movement. Lower the weight down in a controlled slower manner back to the starting position and repeat process.