Relationship between muscle activation and vertebral kinematics in head-neck system of rhesus monkey during voluntary head movement

The purpose of this study was to determine the relationship between neck muscle activation patterns and movements of head and cervical vertebrae. Phase relations between the input stimulus, the sinusoidal motion of the vertebral column, and peak activation of neck muscles were calculated. Results demonstrated that head and cervical vertebrae moved synchronously and that the vertebral movements were quite constant and showed primary movements about skull C₁ and C6-C7 joint axes during pitch motion. Variability in muscle responses did not seem to affect the vertebral motion even though the muscles are the primary actuators of the joint movement. This result suggests that the central nervous system can choose multiple strategies to achieve a single movement