sEMG signals analysis using time-frequency distribution for symmetric and asymmetric lifting

Following the industrial revolution, a third of the world´s economic output is derived from manufacturing industries. In the manufacturing industry sectors, manual lifting is commonly practiced even though mechanized material handling equipment are provided. Due to this repetitive lifting behavior, it will contributes to muscle fatigue and low back pain that can lead to work efficiency and low productivity. This will cause great losses to the company and to the country. The purpose of this study is to investigate changes in the surface electromyography (sEMG) signals during repetitive manual lifting for different twist angle values. The EMG signals are taken from right Biceps Branchii of five healthy subjects (age range 21 - 25 years) while performing symmetric and asymmetric lifting of twist angle 0° and 90° at lifting height of 140 cm with load mass of 10 kg. The analysis is done by applying time-frequency distribution (TFD) which is spectrogram technique to represent the EMG signal in time-frequency representation (TFR) before displaying the instantaneous voltage, V_rms (t) value. This study found that symmetric lifting requires less force to lift the load and that asymmetric lifting has faster tendency to experienced fatigue. This study concludes that the twist angle has a significant influence to the muscle performance of right Biceps Branchii.