Time and Frequency domain analysis of APB muscles Abduction in adult dominant hand using surface electromyography signals

The physiological behavior of the abductor pollicis brevis (APB) muscle during the early stages of fatigue is useful for subsequent clinical assessment of a pathologically altered muscle. In this work, sEMG signals from the Abductor Pollicis Brevis (APB) muscle are analyzed using time and frequency domain features. For this, healthy adult volunteers participated in this study who performed the continuous effortful abduction and adduction from their thumb of the dominant hand under a well-defined protocol. During this, sEMG signals are acquired using a dedicated biomedical data acquisition system. The signals are first pre-processed and then segmented into cycles consisting of adduction and abduction. Two time-domain and two frequency-domain features, namely kurtosis, mean absolute deviation, mean frequency, and median frequency respectively, are extracted. Results show that the APB muscle is active during the abduction phase of the cycle. Further, these cycles are different within the subject and among subjects. The time-domain features, namely mean absolute deviation, have lower values in the last curl. Additionally, the kurtosis, an indicator of Gaussianity, shows higher values in the case of the last curl. The mean and median frequency indicates a lower value in the last curl in most cases. This might be due to muscle fatigue as a result of continuous contraction. The extracted features are able to distinguish between the first and last curl of the experiment. This study could be further extended to analyze pathological conditions such as Carpal Tunnel Syndrome, which affects APB muscle.