Estimation of stress during car race with factor analysis.

Car race drivers are always in dangerous and harsh environments. In order to reduce risks due to mental stress, it is important to evaluate stress during a car race in real-time. The present study measured three physiological indices, heart rate variability, sweat rate, and electromyogram of massester from a professional racer during a car race. However, the relation between these indices, and the types of stress still remains unclear. In the present study, we examined the relations between the three indices and factors linked with these indices during car race with factor analysis. The results suggested that the three physiological indices related to two different factors. One factor scored high when driver saw other nearby car, and was influenced mainly by heart rate variability and sweat rate. We suggest that mental stress is probably high in such scenes, and named this factor as “mental stress”. Furthermore, the other factor showed high values during urgent accelerations and decelerations, and was influenced mainly by electromyogram of massester. During urgent accelerations and decelerations, the driver probably suffered from large physical discomfort. Therefore, we named the second factor as “physical stress”. In summary, we found the three physiological indices reflected two different types of stress during car race. Moreover, according to the results of factor analysis, we proposed a method of real-time estimation of both mental and physical stress with the three physiological indices during car race.