SURFACE ELECTROMYOGRAPHY AS A TOOL TO STUDY THE HEAD REST COMFORT IN CARS

In this study, two methods were presented in order to evaluate objecti vely the comfort of head rests in cars using surface electromyography (SEMG). First, the Amplitude Probability Density Function (APDF) was c omputed. Extremely low level intensity activities were measured. No si gnificant differences were observed on SEMG global activity between ex periments with and without a head rest. Second, instead of computing o ne APDF, several APDF were calculated over time. Analyses focused on t he rate of evolution of APDF parameters. This was a time varying APDF (TAPDF). This last method allowed a better diagnosis than the first on e. For drivers, significant decreases in SEMG activity were observed w hen using a head rest. For passengers, a contradictory increase in SEM G activity was observed during experiments with a head rest. This obse rvation was explained by the seat back angle chosen by passengers.