Dumb-bell bar for e.g. concentration training, has outer hull made from metal with view slot or from transparent material, and balls of different density used in different number and in air or hard liquid in hollow space of bar

摘要

The bar has a hollow cylindrical inside and is filled at both open and closeable ends with balls/grains/sand granules that are freely movable. An outer hull made from a metal with view slot or from transparent material is provided. The balls of different density are used in different number and in air or hard liquid in the hollow space to vary asymmetry force, range and rate of change, where the remaining space is filled by foam plug.