Perturbation-dependent selection of postural feedback gain and its scaling

Area of Science:

• Biomechanics
• Neuroscience
• Human Motor Control

Background:

• Postural control is crucial for maintaining balance during external perturbations.
• Previous research quantified postural feedback gains during support surface translations.
• The effect of different perturbation types on postural feedback gain selection remains unclear.

Purpose of the Study:

• To investigate if postural feedback gain selection and scaling depend on the perturbation type.
• To compare postural responses to forward pushes with responses to support translations.
• To quantify perturbation-dependent feedback gains for forward push perturbations.

Main Methods:

• Seven healthy young adults experienced forward pushes from a pendulum with varying loads (2-10 kg).
• Impulsive force, ground reaction forces, and joint kinematics were measured.
• A full-state feedback control model quantified empirical data to identify feedback gains.

Main Results:

• Gradual gain scaling with increasing push perturbation magnitude was observed, similar to support translation responses.
• A distinct set of feedback gains was identified for forward push perturbations compared to support translations.
• The identified feedback gains minimized the fitting error between empirical data and the control model.

Conclusions:

• The nervous system appears to differentiate between perturbation types when selecting postural feedback gains.
• Perturbation-specific feedback gains likely balance postural stability with joint torque constraints.
• These findings suggest a sophisticated neural adaptation to varying external disturbances for maintaining upright posture.