Abstract: An upper torso augmentation device in which a moment of an arm assembly is tunable by the movement of one or more movable masses. The upper torso augmentation device including an upper arm assembly pivotably coupled to a shoulder assembly, the upper arm assembly including an assisted force mechanism configured to aid in counteracting an effect of gravity upon the upper arm assembly and any payload carried thereby, the assisted force mechanism comprises one or more movable masses configured to move relative to a distal end of the upper arm assembly, thereby affecting a change in a moment of the upper arm assembly.