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Updated: Jul 14, 2026
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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
Anticipatory control of head posture
Alessander Danna-Dos-Santos1, Adriana M Degani, Mark L Latash
1Department of Kinesiology, The Pennsylvania State University, Rec.Hall-267, University Park, PA 16802, USA.
Summary
Neck muscles use two anticipatory postural adjustment (APA) patterns: reciprocal for direct head perturbations and co-activation when direction is uncertain. Leg and trunk APAs minimally contribute to head stabilization.
Area of Science:
- Neuroscience
- Biomechanics
- Motor Control
Background:
- Anticipatory postural adjustments (APAs) are crucial for maintaining stability during voluntary movements.
- Neck muscles play a vital role in head stabilization, but the specific control strategies are not fully understood.
Purpose of the Study:
- To investigate two distinct APA patterns in neck muscles: reciprocal and co-activation.
- To determine if these patterns are task-specific based on perturbation type.
- To explore the role of leg and trunk APAs in head stabilization.
Main Methods:
- Applied head and/or trunk perturbations (loading/unloading) to standing participants.
- Recorded electromyographic (EMG) signals from 10 muscles.
- Analyzed center of pressure shifts and EMG indices for APA quantification.
Main Results:
- A reciprocal (time-shifted) APA pattern was observed in neck muscles during direct head perturbations.
- A co-activation (simultaneous) pattern dominated when trunk perturbations were applied.
- Leg and trunk muscles showed minimal APAs during head perturbations, with no significant difference when the head was also perturbed.
Conclusions:
- Two distinct APA patterns exist in neck muscles, task-specifically employed based on perturbation direction.
- Reciprocal APAs are used for predictable head perturbations, while co-activation is employed when uncertainty exists.
- Leg/trunk APAs appear to have a limited role in stabilizing head posture, suggesting specialized neck control mechanisms.
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