Pike Push-ups
The pike push-up is the pushing drill that most closely mimics a handstand push-up without going fully inverted. The body forms an inverted V (downward dog), directing force into the shoulders far more than a standard push-up. It is the essential bridge between push-ups and the handstand press.
Execution
From a plank, lift the hips until the body forms a sharp inverted V. Legs straight or slightly bent. Head hanging between the arms. Bend the elbows so the head descends toward the floor between the hands; elbows open to the sides naturally (correct here). Forehead or crown approaches the floor. Press back to the V with shoulders and triceps.
Hip angle
The more vertical the torso (hips high), the more it resembles an HSPU and the more the shoulders work. Seek the sharpest V you can.
Progression
Elevate the feet on a chair (elevated pike), then practice wall HSPUs. The muscles and movement patterns are the same.