Footwear; Ground Reaction Forces

Question 1

What are the directional GRF components?

Answer 1

• Fz - vertical component
• Fx - anterior/posterior component (fwds/bkwds)
• Fy - mediolateral component (side to side)

Question 2

What are the stages of the vertical GRF gait?

Answer 2

• Passive peak (Fz1) - weight acceptance, a passive resulting peak from the collision of the body with the floor, coincides with braking phase
• Active peak (Fz2) - resulting from active force applied into the ground during push off phase, coincides with propulsion phase
• Loading Rate - rate at which the ground reaction force develops over time

Question 3

Describe the two phases in anterior/posterior GRF gait

Answer 3

• Braking force - force acting posteriorly at initial foot contact causing momentary deceleration
• Propulsive force - force acting anteriorly from midfoot contact onwards causing the body to accelerate, may also be referred to as push off

Question 4

Describe the medial-lateral GRF gait forces

Answer 4

• Low in magnitude
• Profile shape represents subtle transition from supination to pronation to supination during foot contact