An average human skull can withstand 520 pounds of force before crushing. This human bone is stronger than steel and concrete of the same mass and is almost impossible to crush unless using a heavy object. A cubic inch of bone can bear a load of 19,000 pounds before crushing.
Force is calculated by multiplying the mass by the acceleration of an object. A quite heavy object must be traveling at a significant speed to achieve the force necessary to crush a human skull, and it is not possible for human beings to produce the force required for this experiment.