Choose an appropriate weight dumbbell. Stand with your side to the bench and place the closer leg on the bench in a kneeling position and fix the same side hand onto the edge of the bench. The standing leg is slightly bent. Grab the dumbbell and bend your arm at the elbow at about an 80-degree angle. Hold your elbow at your trunk. Keep your torso firm and your pelvis in a neutral position.
From the starting position stretch your arm backwards and up by contracting your triceps muscles. Your elbow is fixed at one angle throughout the entire movement. Keep your wrist firm throughout the exercise. Return to the starting position in the same way while inhaling. Exhale along with the backwards extension. Keep your torso in a fixed position throughout the entire movement. Do the required number of repetitions and then switch your stance and hands to the other side.
Make sure your torso is fixed without overbending your back at the waist. Keep your elbows in a fixed position throughout the movement and do not swing them to the side. Return to the starting position using a slow, controlled motion and avoid sudden relaxation of your muscle tension.
Choose a lighter weight in the beginning to master the technique well. If possible, exercise in front of a mirror to get into the correct starting position and watch for correct exercise technique.