Human Factors: Handles

The Carpal Tunnel is the path in the wrist that all the nerves travel through to get to the hand and fingers. Carpal Tunnel syndrome is caused by that pathway being constricted. When the wrists are straight, the pathway is open. When wrists are twisted for tasks over long periods of time, it causes problems. When you compress the palm, it causes a loss of blood flow.

Cumulative Trauma Disorder is caused by frequent and extreme joint movement and force.

Vibrations can cause a decrease of blood flow, known as white finger. This is seen with jackhammering, etc.

‘Fiskers’ has the best handles at Bunnings. ‘Osko Good Grips’ are also worth checking out.

Types of Grips:

  • Power Grip (like a fist) = maximum skin contact, good for strength, not precision
    • Mid Flexion = maximum strength. You don’t want a fully closed or fully open grip. Your muscles have the best use of power at medium.
  • Pinch Grip = thumb to index knuckle
  • External Precision Grip = pen grip
  • Internal Precision Grip = Knife + fork grip
  • Ulnar Storage Grip = smart phone grip / thumb dexterity
  • Hook Grip = carrying a bag, hanging on trees – incredibly long term capabilities
  • Natural Position = strength over precision. Okay for power / the elderly, not for precision tasks.

Tao/Chinese cleaver is an example of adaptable grip dependent on the user requiring power or precision.

 

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