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bioRxiv · 10.1101/2024.04.29.591089

The effect of head orientation on vestibular signal-based modulation of paraspinal muscle activity during walking

Li, Y. C.·Lemaire, K. K.·Bruijn, S. M.·Brumagne, S.·van Dieen, J. H.
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Abstract

Vestibulospinal reflexes play a role in maintaining the upright posture of the trunk. Head orientation has been shown to modify the vestibulospinal reflexes during standing. This study investigated how vestibular signals affect paraspinal muscle activity during walking, and whether head orientation changes these effects. Sixteen participants were instructed to walk on a treadmill for 8 min at 78 steps/min and 2.8 km/h in four conditions defined by the presence of electrical vestibular stimulation (EVS) and by head orientation (facing forward and facing leftward), while bipolar electromyography (EMG) was recorded bilaterally from the paraspinal muscles from cervical to lumbar levels. In both head orientations, significant phasic EVS-EMG coherence (p < 0.01) in the paraspinal muscles was observed at ipsilateral and/or contralateral heel strikes. Compared to walking with the head forward, a significant decrease (p < 0.05) was found in EVS evoked responses (i.e., EVS-EMG coherence and gain) when participants walked with the leftward head orientation, with which EVS induced disturbance in the sagittal plane. This overall decrease may be explained by less need of feedback control for walking stabilization in the sagittal plane compared to in the frontal plane. The decrease in coherence was only significant at the left lower vertebral levels and at the right upper vertebral levels around left heel strikes (p < 0.05). Together, these findings confirm the contribution of the vestibular afferent signals to the control of paraspinal muscle activity during walking and indicate that this control is changed in response to different head orientations. Key Point SummaryO_LIVestibulospinal reflexes simultaneously contribute to stabilizing the centre of mass trajectory and to maintaining an upright posture of the trunk. C_LIO_LIHead orientation, which challenges stability via altered visual, vestibular and proprioceptive signals, modifies vestibulospinal reflexes during standing. C_LIO_LITo explore the impact of head orientation during walking, we recorded bilateral surface EMG of cervical to lumbar paraspinal muscles, and characterized coherence, gain and delay between EMG and electrical vestibular stimulation, during walking with head facing forward and leftward. C_LIO_LIWhen walking with head facing leftward, vestibular stimulation caused disturbance in sagittal plane. Phasic response in paraspinal muscles with a significant smaller magnitude was found compared to facing forward. C_LIO_LIOur results agree with the idea that less feedback control is required for walking stabilization in the sagittal plane and confirm that vestibular afference modulates paraspinal muscle activity for trunk control during walking, and this modulation is changed in response to head orientation. C_LI

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Li, Y. C., Lemaire, K. K., Bruijn, S. M., Brumagne, S., van Dieen, J. H.. 2024-05-01. The effect of head orientation on vestibular signal-based modulation of paraspinal muscle activity during walking. https://doi.org/10.1101/2024.04.29.591089

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