>!!Balance BoardA balance board is a device used for recreation, athletic training, brain development, therapy, musical training and other kinds of personal development.
A sphere-and-ring board is a lever, similar to a see-saw, that the user usually stands on, usually with the left and right foot at opposite ends of the board. The user's body must stay balanced enough to keep the board's edge from touching the ground.
A different challenge is presented by each of the four types of balance boards and their subtypes. Some of them can be attempted successfully by three-year-olds and elderly people, and some, because of their speed and incline, are difficult and dangerous for professional athletes.
In their design, what differentiates the four types (and their subtypes) is how unstable each of
them is, i.e., in how many and in which of the three dimensions of space each board turns and/or sways and how freely its fulcrum contacts the board and the ground.