The second vertical GRF peak reflects what major action?

The second vertical GRF peak reflects what major action?

• A. Foot slap
• B. Knee buckling
• C. Push from the plantar flexors to reverse downward movement
• D. Hip flexor deceleration only

Answer: (C)

In gait, the second vertical ground reaction force peak marks the push-off phase powered by the plantar flexors. As you rise onto the toes and push against the ground, the Achilles–soleus–gastrocnemius muscles generate a strong plantar flexion force that reverses the body's downward motion and propels the body upward (and forward). This vertical impulse creates the second peak in the force curve. Foot slap describes the impact at initial contact and shows up as the first peak, not the second. Knee buckling relates to instability at the knee rather than the push-off force, and hip flexor deceleration alone doesn’t account for the vertical propulsion peak produced by plantar flexion.

In gait, the second vertical ground reaction force peak marks the push-off phase powered by the plantar flexors. As you rise onto the toes and push against the ground, the Achilles–soleus–gastrocnemius muscles generate a strong plantar flexion force that reverses the body's downward motion and propels the body upward (and forward). This vertical impulse creates the second peak in the force curve. Foot slap describes the impact at initial contact and shows up as the first peak, not the second. Knee buckling relates to instability at the knee rather than the push-off force, and hip flexor deceleration alone doesn’t account for the vertical propulsion peak produced by plantar flexion.