# A Vestibular Training to Reduce Dizziness
## 4 General Discussion
### Comparing Pre-Test and Post-Test Measurements  
The dizziness response to the strong section-inducing visual stimulation presented via HMD was attenuated after the training compared with the initial assessment. This was the case for the objective as well as for the subjective dizziness measures. The post-rotatory sensations as well as dizziness ratings improved. Additionally, postural stability while exposed to the rotating drum stimulus was improved after training. The path lengths of the CoP of the force plate on which the participants stood were reduced both for mere vertical axis rotation as well as for the added pitch condition, albeit much less so in the pitch condition. This may have been the case due to the fixed order of the stimuli. Since the no-pitch condition was always presented first, the subjects could have become somewhat accustomed to the stimulus, leading to less sway on the balance board which in turn may have left smaller room for improvement in the post-test. We observed the same pattern when comparing the FMS-D ratings right after the visual stimulation in the pre-test and post-test. Again, the subjects improved less in the pitch condition. However, due to our current experimental design, it cannot be ruled out that the training simply had less of an effect on the visual yaw rotation when it was combined with the visual pitch motion.  
The two stability measures taken with the Balance Error Scoring System, the one-leg stance and the Romberg stance, descriptively point toward an improved ability to maintain balance after the training, albeit not a significant one. We also found consistently larger postural sway values for the one-legged stance compared with the two-legged stance. A plausible explanation could lie in the differential amount of vestibular involvement between these conditions. The two-legged stance on the foam pad may have commanded less vestibular control. The surface of contact between the feet and the foam pad was twice as large in the Romberg condition, and the motor feedback loop, which keeps the body balanced, can rely much more on muscles and sinew sensors and is less dependent on vestibular information. The latter presumably played a more decisive role in the one-legged condition, which called for a more rigid posture. Note also that the Romberg test is mainly used to assess vestibular dysfunction and may have been consistently stable for our healthy participants.  
The largest training-related improvement we could observe was in the duration of the post-rotatory dizziness after vestibular stimulation via the rotating chair. The sudden stop of the chair after having been rotated produces a pronounced post-rotatory sensation of spinning in the opposite direction. During the pre-test, this sensation lasted for approximately 10 seconds on average. During the post-test, it lasted for an average of merely five seconds. This is a remarkable decrease. The relative similarity between the rotations practiced during the training sessions and both the pre-test and post-test could be responsible for this impressive effect. The only difference between the spinning segments during training was that the participants were standing as opposed to being seated and spinning actively versus being spun passively. It appears that the training was specific to body rotation but generalized to visually induced feelings of rotation and to postural control. Interestingly, the intensity of dizziness right after the end of the stimulus remained unaltered. Why did the duration of the post-rotatory sensation adapt, whereas the magnitude of the dizziness did not? This may be indicative of the nature of the adaptation process. The adaptation of the duration might be attributable to sensory suppression of the response, whereas the subjective degree of dizziness may be a cognitive response which is affected by expectations and attribution in addition to sensory processes.