Cornell University Ergonomics Web


Manual Materials Handling

Grasps (Grip) - For many activities the interface between a person's hand and an object to be moved is a critical factor. The design of this interface frequently influences the type of grasp that can be used.

Classifications - are made on the basis of the muscles used:

1.    Pinch (Precision) Grip - Characterized by opposition of the thumb and distal (away from the body) joints of the fingers. Allows us a great deal of dexterity and precision adjustment, but, since the proximal finger surfaces (nearest to palm) and the palm are not used, the pinch grip is only about 25% of the maximum grip strength possible (the power grip). Pinch grip strength decreases rapidly at spans less than 1" or greater than 3". Examples include: holding pen or pencil, cartridges in and out of holder, and carrying a tray.

Functional Hand Grasp (Pinch Grip) 
  5th  %ile 50th %ile 95 %ile
True 2.1cm. (.8")  4.3cm. (1.7") 7.9cm. (3.1")
Max.  10.8cm. (4.2")  12.5cm. (4.9") 15.0cm. (5.9")

2.    Power Grip (Cylindrical) - the maximum force that can be developed by the hand. Influenced by wrist orientation and grip span. The thumb may or may not be used. Examples include: carrying pipe, forcing a screwdriver in a disassembly unit, and using hand tools.

3.    Oblique grasp - a variant of the power grasp characterized by gripping across the surface of an object, e.g. carrying a tray with handles -lift up and power grip ends. Oblique grasp is around 65% grip strength of power grasp. Grasp strength is strongly affected by hand span. A grip of around 2 to 2 1/2 " is the strongest. The thumb is very important in this grasp.

Functional Hand Grasp (Oblique Grip) 
  5th  %ile 50th %ile 95 %ile
True 3.6cm. (1.4")  4.6cm. (1.8") 5.8cm. (2.3")

4.    Hook grasp - characterized by a flat hand, curled fingers, and thumb used passively to stabilize the load, e.g. auto steering wheels. Load is supported by fingers. This grip is most effective when the arms are down at the side of the body. For objects with a diameter of 2" the hook grip strength can achieve the strength of a power grip. Very narrow handles decreases hook grip strength by pressing deeply into hand and fingers. Rigid handles should generally be avoided.

5.    Palm-up/ Palm down grasp -

Grasping -

Pushing and Pulling -

  1. Horizontal pushing and pulling - Factors which influence this include: body weight, height of force application, distance of force application from body (amount of trunk flexion/extension), frictional coefficient of floor, frictional coefficient of shoes, duration of force applied or distance moved, availability of structure against which feet or back can push or prevent slippage (e.g. starting blocks).
  2. Vertical pushing and pulling - Factors which influence this include: grip strength and height of force application. The height determines which muscles will be used. Pulls from above head level allow for the greatest force because body weight can be used. Pulls from more than 10 inches above the floor also allow the greatest force because strong leg and trunk muscles can be used. Only 85% of maximum standing vertical forces can be generated for downward pulls when seated.
  3. Transverse (lateral) forces applied horizontally - Pushing across the front of the body involves weaker shoulder muscles so full arm extension leads to a marked decrease in maximum force. For example, maximum transverse forces are only 50-70% of maximum horizontal pushes and pulls for lever operation straight ahead of body at same elbow angle.

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