Having the complex structure, It is impossible to train all the heads of Deltoid muscle with one single exercise. For best results, one has to train on different exercises. Here try 3 best exercises to train all heads of the deltoid optimally.
Dumbbell Shoulder Press
Stand with feet hip-width apart, knees slightly bent and core stabilized. With a dumbbell in each hand, bring your upper arms up until the are even with the sides of the shoulders. Press the dumbbells upward until your arms are extended overhead and lower back to the sides of your shoulders to finish the movement.
Bent Over Row with 45 Degree Inclined Bench
Lying prone on a 45-degree incline bench, let your arms hang straight while holding a dumbbell in each hand. Slowly lift your arms as high as possible by squeezing the shoulder blades together. Throughout the movement, the upper arms should remain perpendicular to the body, with the forearms pointed toward the floor. After reaching the top of the movement, slowly lower the dumbbells back to the starting position.
Rear Lateral Raise
Sit on the edge of a bench with your feet on the floor. While bending over and, if flexibility allows, resting your torso on your thighs, grasp the dumbbells while the arms are extended under your legs. Maintain a flat back position as you slowly raise your arms to your sides until your elbows are at shoulder height. The arms should be perpendicular to your torso, with a fixed elbow position (10° to 30° angle) throughout the exercise. Then slowly lower the dumbbells back to the starting position.