Standing up and sitting down

The sequence of frames of a late middle aged woman standing up from a 40cm high stool illustrates the typical pattern of movement for the sit-to-stand sequence.
The movement sequence can be divided into 3 phases (Severn)

1   Flexion momentum phase:   Flexion at the hips tilts the trunk forwards. The trunk is held in extension with pelvis in neutral tilt.  

     Tilting the trunk forwards moves the COM of the head, arms and trunk (HAT ) in the direction of the feet. (A-B)

STS-2.jpeg

2   Momentum transfer phase:  A rapid transfer of weight from the buttocks to the feet and initiation of action in the lower limb extensor muscles.  (C-D)

At this lift-off  point the  COM continues to move forward and then starts to move upwards as the hips and knees are extended.
The momentum of the trunk movement is transferred to the lower limb extension moments.

This phase ends at the point of maximum dorsiflexion – which identifies the point at which the CoM stops moving forwards.

sit-stand-c_1.jpeg  sit-stand-d_1_0.jpeg

3  Extension phase:  Extension of the hips and knees to bring the body erect.  (E-F)

sit-stand-e.jpeg   sit-stand-f.jpeg

 At the end of the extension phase the momentum of the CoM must be controlled to maintain balance.  (G-H)

sit-stand-g.jpeg   sit-stand-h.jpeg

Maximum ROM 

Maximum ROM (estimated) – in the sequence illustrated below – late middle aged woman – no arthritis 

  • Hip flexion              1350  at the point of lift off
  • Knee flexion            500  just after lift-off as the weight is shifted forwards
  • Ankle dorsiflexion    700  at the end of the forward shift of the CoM

Limiting factors (constraints) that impact on sit-to-stand

Constraints related to the individual

Decreased range of movement 

  • Hip(s) ROM- often associated with osteoarthritis of one or both hips, or following hip joint replacement 
  • Knee ROM - associated with knee injury, arthritis, following joint replacement surgery. 

Muscle weakness, fatigue and joint instability

  • Knee extensor muscle weakness - associated with aging, arthritis, following surgery. 

Poor balance and coordination

  • Associated with aging, general weakness, neurological disorders

Task goals and environmental constraints 

Characteristics of the chair and floor

  • Height of the seat
    Presence of arm rests - for pushing up on 
  • Compliance of the seat 
  • Supporting surface - evenness, slipperiness, compliance

Task goal 

  • Speed of the movement - fast or slow
  • Following action - stand up and walk forwards 
  • Stand up carrying an object 

Foot wear - stability, slipperiness 

Social environment - people or animals that require attention