Explain ankle, hip, and stepping strategies and when each is typically used during perturbations.

• A. Ankle strategy uses ankle torques to sway about the ankles for small perturbations on firm surfaces; hip strategy uses hip and trunk motions for larger perturbations or when ankle stability is limited; stepping strategy involves taking a step to widen the base of support when perturbation is large.
• B. Ankle strategy uses hip/trunk; Hip uses knee; Stepping uses head movement.
• C. Ankle strategy occurs only in supine; hip when standing; stepping when not moving.
• D. Ankle strategy is a cognitive strategy; hip is a reflex; stepping is a brainstem response.

Answer: (C)

When balance is disturbed, the body uses a sequence of correction strategies tailored to how big the disturbance is and how the body can respond while staying upright. The ankle strategy relies on small, in-place ankle torques to shift the center of mass over the base of support. It’s a distal-to-proximal response best for small perturbations on a firm surface, allowing the feet to stay planted while the body leans slightly, with the hips and trunk making only minor adjustments as needed.

The hip strategy kicks in for larger perturbations or when ankle stability is limited. Here the corrections come from more proximal joints—primarily the hips and trunk—moving the upper body to realign over the base of support. This helps generate bigger corrective moments when ankle responses aren’t sufficient or when the surface or ankle conditions constrain ankle torque.

If the perturbation is too large to be managed in place, a stepping strategy is used. Taking a step extends the base of support by placing the foot in a new position to catch the fall and re-center the center of mass within the new stance. Often, stepping is preceded or accompanied by ankle and hip adjustments, especially with rapid or multidirectional perturbations.

In short: small disturbances on solid ground are handled with ankle movements, moderate disturbances recruit the hips, and large disturbances prompt a step to widen the stance. The other descriptions don’t fit how these strategies operate in upright balance.