Proper driving requires a proper posture to bring comfort to drivers. A problem that commonly exists in driving is
incorrect driving posture which can cause discomfort to the driver, especially when interacting with automotive
pedals. Research on fatigue of Soleus muscle on driver's posture based on the knee angle more than 144º in a
position of pressing and releasing a pedal was conducted to investigate and overcome this problem. This is a field
experiment study and surface electromyography (sEMG) is used in collecting data on the Soleus muscle. The
procedure of collecting data on the Soleus muscle before and after experiments follows the Surface
Electromyography for the Non-Invasive Assessment of Muscles (SENIAM) recommendation. The result of the
experiments shows that there is a strong positive relationship between driver's postures in nature based on the angle
of the knee with Soleus muscle contraction, where the Pearson correlation coefficient (r) is .890. While the muscle
fatigue index based on value MDF (MNF) in position of pressing a pedal. The results show that the Soleus muscle
fatigue occurs when the foot pressing a pedal on MVC-normalized 60%. This is because the value of MDF (MNF) there
is displacement of decrease of frequency MDF (MNF), from 130.21 Hz (313.42 Hz) to 127.60 Hz (312.49 Hz). The
increase in the knee angle will directly provide discomfort to the driver while interacting with the pedal; and this is
due to Soleus muscle fatigue.