Finger yoga is hatha yoga for the fingers. Extremities need yoga like every other part of the body. However hands are rarely given much attention in yoga classes - where focus naturally is concentrated on very important areas - such as the spine.
To a certain extent, hands represent a microcosm of the organs of action. They need a slightly different emphasis, perhaps from the other limbs. In particular, they are easier to apply excess force to, and potentially expose more connective tissue to stretching forces.
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