A cushion member having improved variable stiffness for a target is provided. The cushion member comprises a cushion housing having an interior with a variable internal pressure and an exterior surface for receiving the target. The cushion housing is arranged to be deformable and comprises granular particles disposed in the interior of the cushion housing. The cushion housing further comprises hollow particles disposed therein with the granular particles. Each hollow particle is compressible and hollow to define a void therein. The hollow particles have a size, a wall thickness, a material, and a bulk modulus defining infill properties thereof. The hollow particles and the granular particles are arranged to allow the cushion housing to be deformed upon contact with the target. The hollow particles and granular particles define a cushion infill having a variable stiffness based on the infill properties and the variable internal pressure of the interior.