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<p>Muscle conditioning is a protocol that systematically alters the level of resting discharge of muscle spindle afferents, resulting in a relatively high or low muscle spindle afferent discharge. Previous studies have shown that this protocol alters the acuity of limb proprioception in a systematic way. We hypothesized that this protocol will also alter neck proprioceptive acuity, depending on the involvement of vestibular activation. In this pilot study, we investigated whether muscle conditioning alters the accuracy of head-to-trunk joint position sense with and without head position change. Young, healthy blind-folded participants lay on a bench with movement of the head-neck or neck-trunk restricted to the sagittal plane. When supine, the head-neck was rotated about the cervico-thoracic junction. When side-lying, the head was fixed while the trunk was rotated. Participants first memorised a target angle and indicated when they perceived that their head-neck or neck-trunk had reached the target angle. Experiments were performed after conditioning dorsal neck muscles (DNMs) to leave muscle spindles mechanically sensitive or not. Constant (directional) error of the perceived location of the target angle was significantly larger when DNMs were conditioned to leave their muscle spindles mechanically insensitive in the side lying posture only (mean difference between mechanically insensitive and mechanically sensitive DNM spindles of supine 1.5°, <i>p</i> = 0.333; side-lying 7.843°, <i>p</i> &lt; 0.001). For absolute (magnitude of error without reference to direction) error, a significant mean difference between mechanically sensitive and insensitive DNM spindles was only found in the side lying posture (mean difference 4.87°, <i>p</i> = 0.002). The present results suggest that muscle conditioning applied to the DNMs affects head-to-trunk joint position sense. Particularly, reducing the mechanical sensitivity of DNM spindles reduced the accuracy in estimating head-neck to trunk position in both supine and side lying postures, but less so when head movement occurred. This result points to sensory reweighting of vestibular and neck muscle proprioceptive inputs in maintaining the acuity of head-to-trunk position sense.</p>

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A pilot investigation of muscle conditioning as a tool to study neck proprioception and vestibular reweighting during head to trunk movement

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  • 发表日期：

    2025年7月25日

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  • Barbara Polus,
  • Stella Stylianou,
  • Samantha Harman,
  • Dinesh K. Kumar,
  • Nobuhiro Watanabe

摘要

Muscle conditioning is a protocol that systematically alters the level of resting discharge of muscle spindle afferents, resulting in a relatively high or low muscle spindle afferent discharge. Previous studies have shown that this protocol alters the acuity of limb proprioception in a systematic way. We hypothesized that this protocol will also alter neck proprioceptive acuity, depending on the involvement of vestibular activation. In this pilot study, we investigated whether muscle conditioning alters the accuracy of head-to-trunk joint position sense with and without head position change. Young, healthy blind-folded participants lay on a bench with movement of the head-neck or neck-trunk restricted to the sagittal plane. When supine, the head-neck was rotated about the cervico-thoracic junction. When side-lying, the head was fixed while the trunk was rotated. Participants first memorised a target angle and indicated when they perceived that their head-neck or neck-trunk had reached the target angle. Experiments were performed after conditioning dorsal neck muscles (DNMs) to leave muscle spindles mechanically sensitive or not. Constant (directional) error of the perceived location of the target angle was significantly larger when DNMs were conditioned to leave their muscle spindles mechanically insensitive in the side lying posture only (mean difference between mechanically insensitive and mechanically sensitive DNM spindles of supine 1.5°, p = 0.333; side-lying 7.843°, p < 0.001). For absolute (magnitude of error without reference to direction) error, a significant mean difference between mechanically sensitive and insensitive DNM spindles was only found in the side lying posture (mean difference 4.87°, p = 0.002). The present results suggest that muscle conditioning applied to the DNMs affects head-to-trunk joint position sense. Particularly, reducing the mechanical sensitivity of DNM spindles reduced the accuracy in estimating head-neck to trunk position in both supine and side lying postures, but less so when head movement occurred. This result points to sensory reweighting of vestibular and neck muscle proprioceptive inputs in maintaining the acuity of head-to-trunk position sense.