First up is the standard strict overhead press. This method relies solely on the muscular strength of the deltoids, upper chest, and triceps to get the bar from your shoulders to a position fully locked out overhead. If you go to a commercial gym this is the method you're most likely to encounter if you happen to see anyone putting a bar over their head.

Key characteristics of a strict overhead press:

• The knees stay locked and rigid.

• The hips stay locked and may be extended forward slightly with an accompanying slight lay back in the torso.

• The elbows should be pointed down and perpendicular to the floor and situated in a position slightly in front of the barbell to allow for maximum leverage against the resistance.

• The bar should be situated as close to the center of mass (the hips) as possible.

• Prior to the initiation of the press the bar may either be grazing the collarbones or left in a floating position underneath of the chin.

• In either case the entirety of the load is supported by the arms and the upper body alone powers the barbell overhead.

Next up is the jerk. This movement comes from the sport of Olympic weightlifting, and is basically the a polar opposite of the strict overhead press. It uses almost entirely lower body power to get the bar locked out overhead.

Key characteristics of a jerk:

• The bar is locked into the front delts by creating a stable shelf position. 

• The elbows should pointed about 45 degrees or so relative to the floor when in the set position.

• The bar is supported by the torso and the role of the arms is merely to keep it stable.

• The bar should be situated as close to the center of mass (the hips) as possible.
  
  

Together, these characteristics ensure that during the dip and drive phase the legs will be able to impart the greatest amount of power into the barbell, and therefore give it the greatest potential for upward trajectory while still leaving the arms in a position to be able to quickly and efficiently receive the weight overhead.

At this point, as the bar floats upward due to momentum imparted by the lower body musculature, rather than engage the upper body musculature at all, the lifter instead uses this brief moment where the barbell hangs weightlessly in the air as an opportunity to push themselves underneath of it.

They are then able to subsequently receive the bar overhead on fully locked arms with the legs in either a split position or symmetrical squat position, and therefore once again engage the stronger muscles of the legs and hips to bring their body back to a fully erect position, rather than ever relying on the comparably weaker muscles of the upper body to assist in getting the bar overhead.

Employing this method of emphasizing the lower body in a powerful and explosive role, while using the upper body muscles merely to stabilize and guide the bar, allows you to get the most weight overhead in an absolute sense and is therefore the most logical method to employ during competitive circumstances (it is also required by the rules of Olympic weightlifting during weightlifting competition).

Last but not least is the push press. The push press is, in many ways, essentially a combination of these two preceding methods of getting the bar overhead. It is part jerk, part press. It is part lower body, part upper body. This hybrid nature of this exercise makes it unique in that it is a bit easier to easier to learn (compared to a jerk), and it retains many of the benefits of both the strict press and the jerk.

Key characteristics of a proper push press:

• The bar is racked on the front delts similar to the front rack used during a jerk.

• Similarly, an aggressive dip and drive uses the powerful leg muscles to heave the bar up off of the shoulders.

• The bar is then pressed overhead to a fully locked out position using the strength of the deltoids and triceps.
  
  

The primary difference between the push press and the jerk is that after the aggressive dip and drive, rather than shifting your body underneath of the barbell in order to catch it at arms length as you would during a jerk, instead you finish the press overhead by using the strength of the upper body.

The lower body gets the bar going but the upper body finishes things off. This dual nature situates the push press firmly in between the strict press and the jerk in terms of absolute loading capabilities.