Measurements of muscle use during steering wheel manipulation

Knowing the neuromuscular admittance of drivers helps understanding how drivers adapt to different steering wheel configurations. System identification allows, through force perturbations on the steering wheel, for identification of endpoint admittance. Design of the forcing function can greatly influence the obtained results. We conducted an experiment to investigate the effects of frequency content and amplitude on estimated admittance. We also measured electromyography (EMG) activity in order to get an understanding of how the identified endpoint admittance strategies were realized at the level of individual muscle groups. The experiment took place in a fixed base driving simulator with an electrically actuated steering wheel. The results showed that when drivers were asked to be passive in response to force perturbations, amplitude and frequency content had little influence on endpoint admittance and EMG activity. However, resisting the perturbations yielded significantly lower admittance when the perturbations had more frequency content. EMG activity was not much influenced. Hence, we tentatively conclude that too much frequency content above 0.7 Hz suppresses reflexive muscle activity. To prevent this force perturbations for admittance measurements should contain enough power above 0.7 Hz to allow identification but as little as possible so as not to suppress reflexive muscle activity.