Abstract
A simple water plethysmograph with a large water surface is described. The plethysmograph includes mainly the bulk of muscles of the forearm. The commercially available standard sleeves fit most limbs well. The plethysmograph with sleeves can be put on a limb within 2–5 minutes. The improvements made the transmission loss negligible, reduced the hydrostatic pressure applied to the arm, and made the water plethysmograph easy to handle.