Here's why:
* Movement: The shoulder press involves moving the weight vertically, from a position in front of the body to overhead. This motion occurs directly in the sagittal plane.
* Muscle Action: The primary muscles involved in the shoulder press, such as the deltoids and triceps, contract in a manner that primarily affects movement in the sagittal plane.
However, there are some subtle movements in other planes that can occur during the shoulder press:
* Frontal Plane: A slight rotation of the shoulders might occur, particularly in the case of dumbbells, as the arms are brought overhead. This rotation is minimal and primarily focused on maintaining a stable and controlled movement.
* Transverse Plane: The movement of the shoulder blades during the press can involve a slight rotation. This rotation helps to stabilize the shoulder joint and ensure efficient muscle activation.
Therefore, while the overhead shoulder press is primarily a sagittal plane movement, there are minor movements in other planes involved in achieving a proper and controlled lift.
