Prehension/grasp

Grasping Grasping is a part of the prehension, a process of orienting the hand, opening it so that the object fits comfortably, contacting the object, and forming a Arm grip. 

Peckham and colleagues [24] at Case Western Reserve University used chronic percutaneous stimulation of forearm muscles to provide hand grasp, including both palmar and lateral prehension and release, in C5 quadriplegic patients. 

Has no impairment of a hand or finger which interferes with prehension or power grasping ... 

Carrying a brief case is a good illustration of this kind of prehension. Keller et al. found that palmar prehension or tridigital pinch was the most frequently used prehensile pattern for static grasping whereas lateral prehension is used most often for dynamic grasping. 

The finding by Keller et al. (1947) that palmar prehension was the most frequently used pattern and reduction of most prosthetic terminal devices to a single DOF has meant that most prosthetic hands incorporate palmar prehension as the dominant grasp pattern. The persistence of this pattern, combined with a wide width of opening in prosthetic hand designs and its general acceptance over the years tends to support this compromise (Heckathome, 1992). 

A study done at Ae University of California at Los Angeles (UCLA) (Taylor, 1954) on human prehension force indicated that adult males could produce maximum mean forces of 95.6 N (21.5 Ibf) of palmar prehension, 103 N (23.2 Ibf) of lateral prehension, and 4(X) N (90 IbO of cylindrical grasp. In light of another (unpublished) UCLA study that showed that forces up to 68 N (15 Ibf) were needed for carrying out activities of daily living, Peizer et al. (1969) proposed that 68 N (15 IbO be a minimum standard for the maximum prehension force for electric prehensors (Heckathome, 1992). 

Palmar prehension is used to grasp heavy, relatively large objects. The entire hand is wrapped around the object. The thumb opposes the force of the other four fingers. 

Prehension by digitopalmar opposition entails grasp of a small-diameter object by the fingers pressing against the palm. The thumb is not involved. 

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