Mechanics of Reaching and Manipulation

Question 1

Important components: reaching

Answer 1

• Protraction and elevation of shoulder girdle
• Shoulder flexion (fwd), abduction (side), extension (bwd)
• Shoulder external rotation
• Elbow flexion/extension
• Wrist extension with radial deviation
• Opening of hand aperture btw thumb & fingers
• Pronation/supination appropriate to object orientation

Question 2

Important components: grasping

Answer 2

• Extension of wrist and fingers
• Conjunct rotation (flex + abd) of CMC jnt thumb
• Conjunct rotation (flex + abd) of MCP jnt pinky
• Closure of thumb and fingers around object (MCP jnt flexion with IP jnts in some extension)

Question 3

Important components: holding

Answer 3

• Flexion/extension of wrist holding object
• Lifting, placing and rotating objects of different sizes and weights

Question 4

Important components: manipulation

Answer 4

• Flexion/extension of fingers
• Cupping of the hand
• Independent finger flexion/extension (tapping)

Question 5

Adaptive strategies: reaching and manipulation

Answer 5

• Uses intact arm only for all reaching & manipulation tasks
• In fwd reaching, excessive hip flexion, elevation of shoulder girdle, abduction and internal rotation at GH jnt, trunk side flexion to intact side
• Excessive elbow flexion and forearm pronation
• Grasps and releases objects with wrist in excessive flexion
• Excessive aperture btw thumb & fingers for grasp & release
• Extension of CMC jnt of thumb and pronation of forearm for grasp and release
• Flat hand or lack of cupping (i.e. grasping without 4/5th digits)
• Inability to move objects within hand

Question 6

How do we assess impairments in reaching and manipulation?

Answer 6

• Item 6,7 & 8 MAS
• Time taken to complete task
• 9 hole peg test
• Spiral test

Question 7

What joints are responsible for transport in reaching?

Answer 7

Movement at the shoulder and elbow transports the hand in space

Question 8

What joints are responsible for orientation in reaching?

Answer 8

Movement at the forearm and wrist orients the hand in space

Question 9

What joints are responsible for manipulation in reaching?

Answer 9

Movement within the hand grasps, holds and manipulates objects

Question 10

What are bimanual movements?

Answer 10

Bimanual movements involve use of both arms, either symmetrically or asymmetrically (i.e. picking up a tray or opening a jar)

Question 11

What effects grip forces during grasping?

Answer 11

Pen and peg experiment, effect of friction btw grip surface and skin (using things like sandpaper, suede and silk). A decrease in friction btw skin and the object increases grip force, as well as changes in heaviness of the object changing grip force

Question 12

When do preparatory hand grip movements occur?

Answer 12

Preparatory hand grip movements occur when movements are self-initiated, the grip force is less when actions are self-initiated, and preparatory hand grip movements are absent when movements are in response to an imposed change in load