Modular control of varied locomotor tasks in children with incomplete spinal cord injuries

Abstract

Fox EJ, Tester NJ, Kautz SA, Howland DR, Clark DJ, Garvan C, Behrman AL. Modular control of varied locomotor tasks in children with incomplete spinal cord injuries.

Modular control of gait after incomplete spinal cord injury: differences between sides

“…Muscle synergies, also known as motor modules, can be defined as functional units of the nervous system that coordinate the coactivation of different groups of muscles. 16 Recent studies on the modular control of gait have shown that the activation of leg muscles during human locomotion can be reconstructed as a linear combination of four to five muscle synergies, each of which are activated at a different phase of the gait cycle [17][18][19] and underlying a specific biomechanical function. 15,20,21 Neurological impairments may alter the normal functioning of modular control and lead to gait disturbances.…”

Modular Control of Gait in Incomplete Spinal Cord Injury: Preliminary Results

“…As the number of synergies is an input of the NNMF, the algorithm was run using two, three, four and five synergies, for each subject. The variability accounted for (VAF) [15] was calculated as a metric of the similarity between original EMG and EMG reconstructed by multiplying matrix W by matrix H. The optimal number of synergies required to adequately reconstruct the EMG data was defined as the smallest number for which the overall VAF was ≥90% [6,15].…”

“…Several studies have shown that the EMG activity of trunk and leg muscles during human locomotion can be reconstructed as a linear combination of four to five basic modules, each one activated at a different phase of the gait cycle [5]. A module has been hypothesized to represent a functional unit of the nervous system that specifies functionally relevant patterns of muscle activation [6]. These modules, also called muscle synergies, quantitatively define the groups of muscles that are activated synchronously [7].…”

“…The activation of each synergy can be associated with kinematic or biomechanical tasks [8]. It has been recently shown that neurological injuries alter modular control and are associated with walking impairments [6]. For example, it has been observed that post-stroke patients present a lower dimensionality of motor control, i.e., a lower number of synergies, than healthy controls [9,10].…”

“…To this aim, the analysis of muscle synergies can endows clinicians with a synthetic yet functional analysis of muscle activation [12]. So far, only a very few studies about muscle synergies focused in SCI patients have been found in the literature [6,8]. Moreover, the groups of patients in these studies were heterogeneous.…”