Sit down at the end of a flat bench with a dumbbell in both arms using a neutral grip (palms of the hand facing you).
Bend your knees slightly and bring your torso forward, by bending at the waist, while keeping the back straight until it is almost parallel to the floor. Make sure that you keep the head up.
The upper arms with the dumbbells should be close to the torso and aligned with it (lifted up until they are parallel to the floor while the forearms are pointing towards the floor as the hands hold the weights). Tip: There should be a 90-degree angle between the forearms and the upper arm. This is your starting position.
Keeping the upper arms stationary, use the triceps to lift the weight as you exhale until the forearms are parallel to the floor and the whole arm is extended. Like many other arm exercises, only the forearm moves.
After a second contraction at the top, slowly lower the dumbbells back to the starting position as you inhale.
Repeat the movement for the prescribed amount of repetitions.
This exercise can be executed also one arm at a time or alternating (like alternating dumbbell curls)
Alternative Exercises For Seated Bent-Over Two-Arm Dumbbell Triceps Extension