Detection of Local Muscle Fatigue in Writing Task Using Surface Electromyography

Abstract

While doing a cognitive job over extended periods causes muscle fatigue, defined as "a situation in which a muscle's capacity to produce maximum voluntary activity, or to perform a series of repetitive motions, is decreased." It occurs while muscle contraction overshoot’s the ability of the tissue substrate and oxygenation. This condition of fatigue can be improved by resting or performing specific workouts. In the Electromyography (EMG) signal, fatigue is known to produce an increase in amplitude and a reduction in spectral line frequencies. The focus of this research was to identify how muscle fatigue occurs in the forearm muscle following both handwriting (HW) and typewriting (TW). Surface EMG signals (sEMG) for both HW and TW were recorded before and after the task performance. These trials were carried out by allowing participants to write approximately 400-500 words on different days. Three muscles were discovered to be involved in handwriting and typewriting: Flexor Carpi Ulnaris, Flexor Carpi Radialis, and Extensor Carpi Radialis. The surface EMG signal was recorded using four different movements. In both writing studies, the median frequency (MDF) was utilized to measure muscle fatigue. The median frequency's power spectrum was compared before and after the work was completed, as well as with the HW and TW outcomes. The findings revealed that following task completion, the median frequency of the EMG signal decreases, indicating that local muscular fatigue has developed in all of the selected muscles. The results showed that HW produces more fatigue than HW since the median frequency values are considerably lowered after the HW activity with a probability (p = 0.0053) value, whereas TW remained statistically insignificant with (p = 0.1751).