Abstract
The originality of our work has been to create a discomfort situation in laboratory by using a vertical transitional vibration which simulates road short events such as sleeping policemen or trenches. Fifteen healthy subjects (11 men and 4 women) between 20 and 35 years participated in this experiment. The subjects sat on a seat which is fixed on a vibrator bench. Fifteen different seats were tested. The seats have been chosen in the way to modify easily cushion foam thickness and hardness and cushion suspensions. The subjects posture was standardised with hands on thighs. The test lasted about one hour per subject.The transitional vibration has been reproduced forty times for each seat. During the test, electromyograms (EMG) were recorded from six trunk and neck muscles. After each mechanical stimulation, the first stage consisted in counting and comparing the number of EMG bursts for each seat. The initial hypothesis is based on the following relation: the more the number of EMG bursts increases the more the physiological discomfort increases. We have shown that it is possible to define a physiological discomfort index reliable and « repeatable » centred on the electromyographic measurement. This index calculated with all the EMG burst can predict seat transient physiological discomfort through a mathematical model which takes into account seat design parameters.