Defines how the lower arm's roll/twisting is distributed between the elbow and wrist joints.
When the lower arm needs to twist or "roll" for the IK, the rotation can be applied at the wrist or elbow joints or some twist can be applied at both. The lowerArmTwist is a weighting value in the range 0..1 that determines the fraction of the twist applied at the elbow and wrist. For example, a value of zero means the twist should be handled entirely at the elbow, while a value of one means it should be applied entirely at the wrist. The default value of 0.5 distributes the twisting evenly between elbow and wrist.