Place a dumbbell on each side of a flat bench. Place your right leg on top of the end of the flat bench and bend your torso forward from the waist until your chest is parallel to the ground (use your right hand as a support on the other end of the flat bench). Use your left hand to pick up a dumbbell from the floor and hold the weight as you keep your entire back straight (the palm of your hand at this point should be facing your torso). Pull the weight upwards until it reaches the side of your chest. Focus on keeping your upper arm tight by your side and ensuring that your torso remains stationary throughout the course of the motion. Once you have reached the top position and the dumbbell is right by the side of your chest, squeeze the back muscles briefly before slowly lowering the weight back down to the starting position. Repeat for the prescribed number of repetitions and then switch sides to perform the exercise with your other arm.