Contribution of neck proprioception to subjective vertical perception among experts in physical activities and untrained women.

The purpose of this study was to investigate the influence of physical training on subjective vertical perception with the different head positions in order to explore the involving of the neck proprioception. Visual field dependence was assessed using a rod and frame test on women practising judo or dance (international level) or no specific physical activity. Tests were performed with head upright or tilted head to disturb the Z-axis egocentric reference frame. A cluster analysis determined the distribution of visual field independent (VFI) and visual field dependent (VFD) participants. The first result showed no head position effect for the group of judoists (6 degrees +/-5 degrees ; 7 degrees +/-5 degrees ) and dancers (4 degrees +/-2 degrees ; 5 degrees +/-3 degrees ) but a significant effect for untrained participants (5 degrees +/-2 degrees ; 7 degrees +/-3 degrees ): their visual vertical perception was more disturbed with tilted head than with head upright. A variability exists among experts and would necessitate further analysis. The second result showed no influence of the head position for all VFD participants, whereas for VFI participants significant difference between upright and tilted head appeared both for experts (3 degrees +/-1 degrees ; 4 degrees +/-2 degrees ) and untrained participants (3 degrees +/-1 degrees ; 5 degrees +/-2 degrees ). In this research, whatever physical activity level, the VFI participants would mainly use the Z-axis reference frame and rely on proprioceptive information. VFD among experts and VFI among untrained participants suggest that proprioceptive reference frame of neck may not provide alone according the groups an appropriate postural control.