Consequences of Car Driving on Foot and Ankle Mobility and Reflexes

Car driving could induce fatigue and an altered sensorimotor control of foot muscles. Also, the use of a cruise controller (CC) or an adaptive cruise controller (ACC) could delay the brake reaction time when an emergency braking response is needed. The literature brings very few information on fatigue of the leg muscles during prolonged car driving and no data was found on any lengthened brake reaction time in CC/ACC condition. We recently showed that 1 hour driving at constant speed (120 or 60 km/hour) induced fatigue of the tibialis anterior (TA) muscle. TA fatigue was associated with a reduced myotatic reflex, a situation which reduced the sensorimotor control of muscles maintaining the foot on the accelerator pedal. Driving in CC/ACC condition increased the amplitude of leg displacement during emergency braking and markedly lengthened the brake reaction time, increasing the braking distance. The brake reaction time increased with age in the CC/ACC condition. Thus, car driving modifies the sensorimotor control of foot muscles and the use of new tools to control the speed of a motor vehicle significantly lengthens the brake reaction time. This could result from an increased amplitude of leg motion and/or an age-related decrease in reflex control.