Which axis represents the anterior-posterior GRF component?

Which axis represents the anterior-posterior GRF component?

• A. X-axis
• B. Y-axis
• C. Z-axis
• D. None

Answer: (B)

In biomechanics, axes are defined by the directions of movement they represent: side-to-side, front-to-back, and up-down. In the common gait-analysis convention, X is mediolateral (side-to-side), Y is anteroposterior (front-to-back), and Z is vertical (up-down). The ground reaction force component that points front-to-back—the anterior-posterior part—acts along the Y axis. The other axes correspond to sideways (X) and vertical (Z) components, so they don’t represent front-to-back movement.

In biomechanics, axes are defined by the directions of movement they represent: side-to-side, front-to-back, and up-down. In the common gait-analysis convention, X is mediolateral (side-to-side), Y is anteroposterior (front-to-back), and Z is vertical (up-down). The ground reaction force component that points front-to-back—the anterior-posterior part—acts along the Y axis. The other axes correspond to sideways (X) and vertical (Z) components, so they don’t represent front-to-back movement.