10.3 Sit to Stand

Question 1

What are the three main requirements for the sit-to-stand task?

Answer 1

Progression, stability, and adaptation.

Question 2

How many sit-to-stand movements does an adult typically perform each day?

Answer 2

About 60 times per day.

Question 3

What does “progression” refer to in the sit-to-stand task?

Answer 3

Generating sufficient joint torque to rise.

Question 4

What does “stability” mean in sit-to-stand analysis?

Answer 4

Moving the center of mass from the chair base of support to the feet.

Question 5

What does “adaptation” refer to in the sit-to-stand movement?

Answer 5

Modifying movement strategies for environmental factors (chair height, armrests, surface).

Question 6

What are the four phases of the sit-to-stand movement?

Answer 6

Flexion momentum, momentum transfer, extension (lift-off), and stabilization.

Question 7

When does the flexion momentum phase begin and end?

Answer 7

Begins with trunk flexion initiation and ends just before buttocks lift off the seat.

Question 8

Which muscle controls trunk flexion during the flexion momentum phase?

Answer 8

The erector spinae, contracting eccentrically.

Question 9

What happens during the momentum transfer phase?

Answer 9

Buttocks lift off; momentum transfers from upper to total body as COM moves to feet.

Question 10

Why is the momentum transfer phase the least stable phase?

Answer 10

The center of mass moves away from the base of support, increasing instability.

Question 11

Which muscles are primarily active during the momentum transfer phase?

Answer 11

Co-activation of hip and knee extensors.

Question 12

What happens during the extension (lift-off) phase?

Answer 12

The hips and knees extend concentrically to raise the body vertically.

Question 13

When does the stabilization phase occur?

Answer 13

After hip extension is complete, when upright balance is achieved.

Question 14

What is the “momentum transfer strategy” in sit-to-stand?

Answer 14

Using forward trunk flexion to generate momentum before lift-off to assist rising.

Question 15

What are the advantages and disadvantages of the momentum transfer strategy?

Answer 15

Advantage: Reduces leg force needed. Disadvantage: Decreases stability during transition.

Question 16

What is the “zero momentum strategy”?

Answer 16

Flexing the trunk to bring the COM over the feet before lift-off, then rising vertically without momentum.

Question 17

What are the pros and cons of the zero momentum strategy?

Answer 17

Advantage: Greater stability. Disadvantage: Requires greater lower extremity force.

Question 18

What effect does using armrests have on sit-to-stand?

Answer 18

Increases stability and reduces hip and knee extension moments by about 50%.

Question 19

Which muscles prepare the feet and tibia during sit-to-stand?

Answer 19

Tibialis anterior positions the feet backward and stabilizes the tibia.

Question 20

Which muscles activate together during lift-off?

Answer 20

Hip and knee extensors.

Question 21

Which muscles assist with postural control during sit-to-stand?

Answer 21

Gastrocnemius and soleus.

Question 22

How do older adults typically adapt their sit-to-stand performance?

Answer 22

Use slower speed, armrests, or reduced momentum strategies for stability.

Question 23

How does muscle activation differ between standing up and sitting down?

Answer 23

Sit-to-stand uses concentric contractions; sit-down uses eccentric contractions.

Question 24

How does lowering the seat height affect sit-to-stand?

Answer 24

Increases hip, knee, and ankle displacement and makes the task more demanding.

Question 25

What is the minimum seat height for elderly individuals to rise successfully?

Answer 25

About 120% of lower leg length.

Question 26

How does seat design affect sit-to-stand performance?

Answer 26

A posteriorly slanted seat shifts COM backward and makes rising more difficult.

Question 27

How does movement speed affect sit-to-stand performance?

Answer 27

Faster movements increase hip, knee, and ankle flexion and shorten total movement time.

Question 28

How does foot placement affect sit-to-stand time?

Answer 28

Posterior foot placement shortens movement time; anterior placement lengthens pre-extension phase.

Question 29

Which strategy ensures greater stability but requires more force?

Answer 29

The zero momentum strategy.

Question 30

What clinical abilities does the sit-to-stand task assess?

Answer 30

Strength, balance, coordination, and neuromuscular control.