Muscle synergy analysis during the sit-to-stand movement in elderly individuals with a history of falling
Objective To explore the change of muscle recruitment mechanisms during sit-to-stand(STS)movements in elderly individuals with a history of falls.Methods A total of 17 healthy young adults,17 healthy elderly adults,and 9 elderly individuals with a history of falls were recruited.Surface electromyography(sEMG)signals and the trajectory of the center of pressure(COP)from 16 muscles of the right lower limb were collected.Falls Efficacy Scale-International(FES-I)was used to assess fall risk,and muscle synergies were extracted by non-negative matrix factorization(NNMF).Results There was no significant difference in the number of muscle synergies among the three groups.In the elderly individuals with a history of falls,early activation of the hamstring and ankle plantar flexors at the beginning of sit-to-stand movement was transformed into additional muscle activity at the later stage of movement,in contrast to the healthy group.Furthermore,COP offsets and FES-I scores were significantly increased,indicating a lack of movement stability.Conclusions Abnormal activation of hamstrings and ankle dorsiflexion in elderly individuals with a history of falls during STS movements may affect lower limb stability and changes in muscle recruitment strategies.
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