I call theses rubber balls (pictured above) with points “nubby balls”. Nubby balls are pliable air filled balls with rubber tips all around the surface. I recommend these to my patients all the time to relieve tightness and pain in many parts of the body.
There are many sizes of balls to choose from. All are great and the smaller they are the more they focus pressure on one particular spot. I may open the sole of my foot with a larger one, then go after a particular trigger point with a tiny one.
Be sure when you are choosing a ball, that they don't squeak if they are a dog toy, and that the nubs are a soft rubber, and not a hard plastic. These are difficult to find and I hope to carry them soon on my website.
By applying your body weight through these nubby balls and maintaining pressure on your muscles, ligaments, tendons, or fascia, you can relieve pain and release tight structures. The applied pressure alone can help to release the tight muscles, relieve trigger point pain, and bring blood flow and nutrients into tight and restricted tissues. However, on a more advanced level, the nubs help to catch the skin, and if pressed deep enough, they catch the fascia. Holding the ball in place over a spot, with an angular pull and pressure away from tightness, for a prolonged pull, can even effect some self myofascial release techniques by tugging on the tight fascia. Instruction by a physical therapist on this technique is recommended first. Though it is a wonderful tool in your toolbox for future issues once you get the technique down.
This, is a whole new ball game!