Functional Degrees of Freedom

Li, Zong Ming

doi:10.1123/mcj.10.4.301

Cited by 41 publications

(27 citation statements)

References 39 publications

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“…Neuromuscular input allows DOF 'freezing' through segmental coupling, providing a reduced subset of control units described using functional DOF (James & Bates, 1997;Li, 2006) and synergies, though the number of mechanical DOF does not change (Chvatal & Ting, 2012;Diedrichsen, Shadmehr, & Ivry, 2009;Todorov, 2006;Turvey, 1990). Mathematically, synergies are defined by systematic correlations among effectors (muscles, joints, or limbs), which characterize coordinated movement (Diedrichsen et al, 2009;Latash, 2010).…”

Section: Introductionmentioning

confidence: 99%

Neuromechanical synergies in single-leg landing reveal changes in movement control

Nordin

Dufek

2016

Human Movement Science

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Section: Introductionmentioning

confidence: 99%

Neuromechanical synergies in single-leg landing reveal changes in movement control

Nordin

Dufek

2016

Human Movement Science

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“…Recently, a technique has emerged that is capable of decomposing EMG patterns recorded from numerous muscles into the summed activation of just a few muscle synergies (Ting and McKay 2007;Tresch et al 1999). Muscle synergies represent the global temporal and spatial organization of the motor output (Li 2006) and provide an attractive simplified strategy for the control of complex movements because they reduce the number of output patterns that the nervous system must specify for a large number of muscles (Raasch and Zajac 1999). For example, five muscle synergies account for the majority of variability in the surface EMG signals of 32 muscles during walking ) and running (Cappellini et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Effect of power output on muscle coordination during rowing

et al. 2011

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The present study was designed to quantify the effect of power output on muscle coordination during rowing. Surface electromyographic (EMG) activity of 23 muscles and mechanical variables were recorded in eight untrained subjects and seven experienced rowers. Each subject was asked to perform three 2-min constant-load exercises performed at 60, 90 and 120% of the mean power output over a maximal 2,000-m event (denoted as P60, P90, and P120, respectively). A decomposition algorithm (nonnegative matrix factorization) was used to extract the muscle synergies that represent the global temporal and spatial organization of the motor output. The results showed a main effect of power output for 22 of 23 muscles (p values ranged from <0.0001 to 0.004) indicating a significant increase in EMG activity level with power output for both untrained and experienced subjects. However, for the two populations, no dramatic modification in the shape of individual EMG patterns (mean r (max) value = 0.93 ± 0.09) or in their timing of activation (maximum lag time = -4.3 ± 3.8% of the rowing cycle) was found. The results also showed a large consistency of the three extracted muscle synergies, for both synergy activation coefficients (mean r (max) values range from 0.87 to 0.97) and muscle synergy vectors (mean r values range from 0.70 to 0.76) across the three power outputs. In conclusion, despite significant changes in the level of muscle activity, the global temporal and spatial organization of the motor output is very little affected by power output on a rowing ergometer.

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“…The functional degrees of freedom (DOFs) in these movements are two, one for each joint (Li 2006). This system is relevant in many functional tasks and has been investigated in several rehabilitation strategies for recovery of function (e.g., Popovic et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Identifying Representative Synergy Matrices for Describing Muscular Activation Patterns During Multidirectional Reaching in the Horizontal Plane

Muceli

Boye

d’Avella

et al. 2010

Journal of Neurophysiology

157

141

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Muceli S, Boye AT, d'Avella A, Farina D. Identifying representative synergy matrices for describing muscular activation patterns during multidirectional reaching in the horizontal plane. J Neurophysiol 103: 1532-1542, 2010. First published January 13, 2010 doi:10.1152/jn.00559.2009. Muscle synergies have been proposed as a simplifying principle of generation of movements based on a low-dimensional control by the CNS. This principle may be useful for movement restoration by, e.g., functional electrical stimulation (FES), if a limited set of synergies can describe several functional tasks. This study investigates the possibility of describing a multijoint reaching task of the upper limb by a linear combination of one set of muscle synergies common to multiple directions. Surface electromyographic (EMG) signals were recorded from 12 muscles of the dominant upper limb of eight healthy men during single-joint movements and a multijoint reaching task in 12 directions in the horizontal plane. The movement kinematics was recorded by a motion analysis system. Muscle synergies were extracted with nonnegative matrix factorization of the EMG envelopes. Synergies were computed either from the single-joint movements to describe the two degrees of freedom independently or from the multijoint movements. On average, the multijoint reaching task could be accurately described in all the directions (coefficient of determination Ͼ0.85) by a linear combination of either four synergies extracted from the individual degrees of freedom or three synergies extracted from multijoint movements in at least three reaching directions. These results indicate that a large set of multijoint movements can be generated by a synergy matrix of limited dimensionality and common to all directions if the synergies are extracted from a representative number of directions. The linear combination of synergies may thus be used in strategies for restoring functions, such as FES.

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Functional Degrees of Freedom

Cited by 41 publications

References 39 publications

Neuromechanical synergies in single-leg landing reveal changes in movement control

Neuromechanical synergies in single-leg landing reveal changes in movement control

Effect of power output on muscle coordination during rowing

Identifying Representative Synergy Matrices for Describing Muscular Activation Patterns During Multidirectional Reaching in the Horizontal Plane

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