Evidence of muscle synergies during human grasping

Abstract

Motor synergies have been investigated since the 1980s as a simplifying representation of motor control by the nervous system. This way of representing finger positional data is in particular useful to represent the kinematics of the human hand. Whereas so far the focus has been on kinematic synergies, that is common patterns in the motion of the hand and fingers, we hereby also investigate their force aspects, evaluated through surface electromyography (sEMG). We especially show that force-related motor synergies exist, i.e., that muscle activation during grasping, as described by the sEMG signal, can be grouped synergistically; that these synergies are largely comparable to one another across human subjects notwithstanding the disturbances and inaccuracies typical of sEMG; and that they are physiologically feasible representations of muscular activity during grasping. Potential applications of this work include force control of mechanical hands, especially when many degrees of freedom must be simultaneously controlled.

Analyzing finger interdependencies during the Purdue Pegboard Test and comparative activities of daily living

“…Although the complex correlated movements of the hand have been investigated in previous studies, most paradigms have included a wide set of tasks and grasping patterns, and were not specific enough to be compared with individual grip styles and existing assessment methods 20,21,51,52 . Moreover, although synergistic movement has been studied during sophisticated uses of the hand, investigations into how movement patterns are assessed by traditional dexterity tests and how it translates into daily living tasks were still lacking.…”

“…Simultaneous correlated motion at multiple joints has been studied during more dexterous uses of the hand, such as typing 16 , playing the piano 17 , and haptic interactions 18 , but a standard procedure to assess such movement synergies has not been developed. Moreover, previous studies involved sets of tasks and hand postures or force patterns that were not specific enough to be immediately translated into assessment practice [19][20][21] .…”

Generating Human-Like Velocity-Adapted Jumping Gait from sEMG Signals for Bionic Leg’s Control

“…Several feature projection techniques, such as Nonnegative Matrix Factorization (NMF) [24], Principal Component Analysis (PCA) [25], Independent Component Analysis (ICA) [26], Linear Discriminant Analysis (LDA) [27], and nonlinear projections [28], can be used to extract muscle coordination pattern. NMF is commonly used as descriptive measure of specific time-invariant muscle synergies because of relaxed constraints on orthogonality and statistical independence between each component and relative robustness to noisy data [24].…”

Towards an understanding of motor system impairments in individuals with unilateral lateral epicondylalgia

“…The complexity of the motor control of the forearm during gripping is amplified due to the large number of muscles available (many degrees of freedom) than are actually required (Castellini & van der Smagt, 2013). In order to simplify this complexity, one theory proposes the idea of muscles synergies (a.k.a motor modules), which are defined as groups of muscles that are activated collectively, that may reduce the many degrees of freedom controlled by the CNS (d 'Avella & Bizzi, 2005;Overduin, d'Avella, Carmena, & Bizzi, 2012;Ting & McKay, 2007).…”

“…This is because the finger flexor muscles, that generate the force of gripping, cross multiple joints and their actions at the wrist must be opposed by the antagonist wrist extensor muscles to maintain the position of that joint (Snijders et al, 1987). Although this could most simply be achieved by activation of the ECRB, ECRL and ECU muscles, that do not cross the finger joints, the coordination is complicated by muscle redundancy with many more muscles available (degrees of freedom) than are actually required (Castellini & van der Smagt, 2013). In order to resolve this complexity, groups of muscle that are activated in synchrony (referred to as muscle synergies or motor modules) have been suggested to represent "building blocks" that may reduce the degrees of freedom controlled by the central nervous system (d 'Avella & Bizzi, 2005;Overduin et al, 2012;Ting & McKay, 2007).…”