A Comparative Analysis of Muscle Synergies in Upper Limb Amputees at Different Stages of Recovery and the Able-bodied Based on EMG Signal Processing

Nowadays, most of the research on the rehabilitation of upper limb amputees focuses on the control and design of prostheses, with increasing advancements in the production of multifunctional, self-recognizable, durable, and intuitive prosthetic devices. Nevertheless, few studies have been concerned about how the muscle activity in the upper residual limb gradually reconfigures itself throughout the different stages of rehabilitation. This paper explores the realignment and reconstruction of residual muscle synergies in upper limb amputees through the neuromuscular system during long-term rehabilitation. The muscle synergies in the upper limb of amputees at different stages of rehabilitation are extracted from Electromyography signals obtained from public datasets using non-negative matrix factorisation, and compared with those of able-bodied individuals for comparative and similarity analyses. The findings show that after extended rehabilitation, the muscle synergy patterns of the upper limb amputee become increasingly complex, balanced, and similar to those of able-bodied individuals, particularly in terms of primary synergy, whereas the amputee with shorter rehabilitation periods still exhibits a more rudimentary and dependent muscle synergy structure. This study provides a comprehensive understanding of the changes in muscle synergies of upper limb amputees during the rehabilitation process and offers a scientific basis for clinical rehabilitation practice.