The surface of the RumbleRoller contains specially designed bumps that are firm, but flexible, much like the thumbs of a massage therapist. As you roll over the top of the RumbleRoller, the bumps continuously knead the contours of your body, gently stretching soft tissue (muscle and fascia) in multiple directions. This action erodes trigger points, helps restore flexibility, and brings quick relief to common types of muscular pain. By design, the RumbleRoller's bumps are firmer than muscle tissue, but much softer than bone, so they deflect out of the way if they contact your spine or other bony protrusions. Through simple techniques, you can control the amount of pressure the bumps apply to your body. The bumps are closely spaced to one another (< 2" apart), so several of them simultaneously contact your body during most exercises. However, with a slight shift of your body, you can reduce your area of contact with the RumbleRoller, which increases pressure and provides deeper, more penetrating relief.