Why are there no ground reaction forces during swing phase?

Why are there no ground reaction forces during swing phase?

• A. The foot is not in contact with the ground
• B. The ankle is dorsiflexed
• C. The knee is extending
• D. The hip is flexing

Answer: (A)

Ground reaction forces only exist when the foot is in contact with the ground. During swing phase the foot is lifted and traveling through the air, so there is no ground contact to push back against, and the ground reaction force is effectively zero. The joint positions described (ankle dorsiflexion, knee extension, hip flexion) occur while the limb is not bearing weight, but they don’t create ground reaction forces because there’s no ground contact. Once the foot lands and stance begins, ground reaction forces reappear as the body pushes against the ground.

Ground reaction forces only exist when the foot is in contact with the ground. During swing phase the foot is lifted and traveling through the air, so there is no ground contact to push back against, and the ground reaction force is effectively zero. The joint positions described (ankle dorsiflexion, knee extension, hip flexion) occur while the limb is not bearing weight, but they don’t create ground reaction forces because there’s no ground contact. Once the foot lands and stance begins, ground reaction forces reappear as the body pushes against the ground.