Multi-finger pressing synergies change with the level of extra degrees of freedom

Sohit Karol, You Sin Kim, Junfeng Huang, Yoon Hyuk Kim, Kyung Koh, Bum Chul Yoon, Jae Kun Shim

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The purpose of this study was to test the principle of motor abundance, which has been hypothesized as the principle by which the central nervous system controls the excessive degrees of freedom of the human movements, in contrast to the traditional negative view of motor redundancy. This study investigated the changes in force stabilizing and moment stabilizing synergies for multi-finger pressing tasks involving different number of fingers. Twelve healthy subjects produced a constant pressing force while watching visual feedback of the total pressing force for the fingers involved in each task. Based on the principle of motor abundance, it was hypothesized that the multi-finger synergies for the total force stabilizing synergy and the total moment stabilizing synergy would be greater as the number of task finger increases. Force stabilizing and moment stabilizing synergies were quantified using the framework of the uncontrolled manifold analysis. It was found that strong force stabilizing synergies existed for all the finger combinations. The index of force stabilizing synergies was greater when the task involved more number of fingers. The index of moment stabilizing synergies was negative for the two-finger combination, representing moment destabilizing synergies. However, the index of moment stabilizing synergies was positive for three-finger and four-finger combinations, representing strong moment stabilizing synergies for these finger combinations. We interpret the findings as an evidence for the principle of abundance for stabilization of both, total force as well as total moment.

Original languageEnglish
Pages (from-to)359-367
Number of pages9
JournalExperimental Brain Research
Issue number3
Publication statusPublished - 2011 Feb

Bibliographical note

Funding Information:
Acknowledgments This study was supported in part by Maryland Industrial Partnerships (MIPS) Program, Seoul Olympic Sports Promotion Foundation of the Ministry of Culture, Sports and Tourism of Korea, Kyung Hee University International Scholars Program, and University of Maryland Department of Kinesiology Graduate Research Initiative Project (GRIP) Award.


  • Degrees of freedom
  • Finger
  • Motor abundance
  • Motor redundancy
  • Synergy

ASJC Scopus subject areas

  • General Neuroscience


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