Smit G , Bongers RM, Van der Sluis CK, Plettenburg DH. Efficiency of voluntary opening hand and hook prosthetic devices: 24 years of development? J Rehabil Res Dev. 2012;49(4):523–34.http://dx.doi.org/10.1682/JRRD.2011.07.0125

Figure 4. Maximum cable activation force to open devices 50 mm during test 2. *Becker Imperial hand (Becker Mechanical Hand Co; St. Paul, Minnesota) was only tested without cosmetic glove. SVO = soft voluntary opening, VO = voluntary opening.