Postural Control (Ankle, Hip, Stepping Strategies)

Balance is the sensory side; postural control is the motor side — the set of muscular responses that keep the center of mass over the base of support. When the body is disturbed (by sway or an external push; see Perturbation Training), the nervous system selects among classic strategies, scaled to the size and speed of the disturbance:

• Ankle strategy — for small, slow disturbances on a firm surface. The body sways about the ankle joint like an inverted pendulum, correcting with the plantarflexors and dorsiflexors (see Foot / Ankle Range of Motion). Most economical; preserves the base of support.
• Hip strategy — for larger or faster disturbances, or on a narrow/compliant surface where ankle torque is limited (e.g., standing on a beam). Rapid hip flexion/extension shifts the center of mass over the feet (see The Hip Complex).
• Stepping (and reaching) strategy — when the center of mass is driven beyond the limits of the base of support, the person takes a corrective step (or grabs support) to establish a new base. The speed and accuracy of this protective step is a strong predictor of whether a perturbation becomes a fall.

Anticipatory postural adjustments (preparatory activation before a voluntary movement, like before raising an arm) and reactive responses (after an unexpected push) are both part of postural control. Training that improves the timing and amplitude of these strategies — especially reactive stepping via perturbation work — translates most directly to fall avoidance (see Fall Prevention for Older Adults (Overview)).

• Strategies scale with disturbance size: ankle → hip → stepping.
• Ankle strategy: small/slow, firm surface; inverted-pendulum sway about the ankle.
• Hip strategy: large/fast disturbances or narrow/compliant surface.
• Stepping/reaching strategy: when COM exceeds the base of support; protective step quality predicts fall vs recovery.
• Includes both anticipatory (feed-forward) and reactive responses.