Muscle Synergy Structure Consistency During Lifting Motion with Exoskeleton

As a wearable robotic device, the exoskeleton may have promising potential to reduce human muscle fatigue caused by lifting motion. In such a case, investigating the muscle synergy structure consistency with and without the exoskeleton is of great importance. However, due to the complexity of human central nervous system, this issue has not been fully addressed. To this end, this paper commits its interest on investigating the consistency of the muscle synergy patterns during human lifting motion with (EXO) and without (No-EXO) a passive exoskeleton. Firstly, eight subjects are recruited to complete lifting tasks during two conditions. Then, the sEMG obtained from seven different muscles of each subject are recorded and decomposed by the non-negative matrix factorization algorithm into muscle synergy relative weighting parameters and muscle activation coefficients. Afterwards, the Pearson Correlation Coefficient (PCC) is used to evaluate the similarity between two muscle synergy vectors composed by the decomposed weighting parameters under two conditions. The experimental results reveal that the muscle synergy structures are consistent in these two cases. This discovery indicates that exoskeleton would not change the muscle synergy pattern during human lifting motion, which could provide meritorious clues on designing and controlling in the field of exoskeleton-human cooperation.