Limitations of Somatosensory Feedback in Control of Posture and Movement

Abstract The sections in this article are: Some Properties of Servomechanisms Loop Gain Frequency Transfer Function Properties of Different Loads Vector Representation of Frequency Transfer Function Vector Representation of a Delay Combination of Different Vectors A Velocity‐Sensitive Transducer A Low‐Pass Filter Stability Nonlinear Systems Response of Limbs to Sinusoidal Movements Effects of Limb Mass Resistance of Muscles to Movement The Two Components of Muscle Force Muscles as Low‐Pass Filters Timing of Reflex Force Timing of Muscle Spindle Afferent Activity Reflex Delay Summary Negative Stiffness and Spontaneous Oscillations Factors Affecting Stability of Stretch Reflexes Nature of the External Load Level of Muscle Activation Resistance to Movements of Different Amplitudes Comparing the Stretch Reflex With a Man‐Made Control System Stability of a Man‐Made System Stability and Gain in the Stretch Reflex Summary Reflex Responses or Precomputed Activity? Response to a Sudden Disturbance Tuning of the Neuromuscular System Triggered Responses to a Disturbance Summary Servo Assistance of Voluntary Movements Precomputed Movements Summary Feedback and Learning Forward‐Looking Control Systems Conclusions