Gymnastic tool, apparatus and method to carry out it

A unitary gymnastic tool consisting essentially of:

• at least two interior chambers, a first chamber defined by a first impermeable external wall, and a second chamber defined by a second impermeable external wall;
• the first and second external walls having facing edges, a planar connecting wall disposed between the facing edges;
• the planar connecting wall fixing the respective edges together so as to make the external walls inseparable, the fixed first impermeable external wall and second external wall forming the unitary gymnastic tool, and,
• wherein at least the first impermeable exterior wall is in the form of a truncated sphere having a circumferential angle greater than 180° and less than 360°;
• and wherein the planar connecting wall is a planar impermeable separator which separates the first chamber from the second chamber;
• and further comprising at least two valves, each valve mounted to a respective external wall for admitting a fluid to each of the two separated chambers.