The military press primarily works your shoulders, but also hits your triceps, traps and core muscles. What makes the military press different from a regular overhead press is that it's performed standing up, with your feet close together and without the use of any leg power. Traditionally military presses are performed with a barbell, though performing them with dumbbells also has many benefits.
Fine Tuning Your Techniques
The techniques for both lifts are very similar, the only difference being whether you use dumbbells or a barbell. In both variations, stand with your feet slightly narrower than shoulder-width apart and hands gripping the barbell or dumbbells at shoulder height. Press your arms up forcefully until your elbows and shoulders are locked out, then lower your hands back to your shoulders. Keep your core muscles, glutes, legs and upper-back tight during both exercises.
The Strength Factor
The main benefit of using a barbell is that you can lift more weight, notes strength coach Jimmy Pena on the Muscle & Fitness website. This enables you to progress faster and build more muscle mass. The only downside to this however, is that while the increased strength may be beneficial, your stronger arm can often end up doing more of the work, which can lead to unbalanced muscle development.
Maximum Muscle Activation
In a study published in a 2013 edition of the "Journal of Strength and Conditioning Research," standing dumbbell military presses were shown to elicit the highest amount of shoulder muscle activation when compared with seated dumbbell presses and seated and standing barbell presses. This was despite the fact that out of the four exercises, the participants' single-rep maximum was lowest on the standing dumbbell press.
What You Need To Do
Ultimately, which variation you pick comes down to you. It appears that barbell military presses are best for strength development, while the dumbbell version is superior for isolating the deltoids. The best idea is probably to include both in your workouts, either by alternating from one session to the next, or performing barbell presses for one to two months, then switching to dumbbells for the same duration. Personal factors will come into it too. If you're an Olympic weightlifter, for instance, barbell presses will have more carryover for your goals, whereas if you've suffered shoulder injuries in the past, you may find dumbbell presses allow you to work your shoulders in a more comfortable, pain-free way.