EMG-based Indicators of Muscular Co-Activation during Gait in Children with Duchenne Muscular Dystrophy

Muscular weakness is one of the main signs associated with the onset and progression of Duchenne Muscular Dystrophy. During motor functions, this disease also determines deviations in muscular activity, especially in terms of coordination and activation between muscles acting on the same joints. In this study, surface EMG activity of the lower limb muscles of 10 children with Duchenne Muscular Dystrophy at different times from disease onset were recorded along with kinematics during unconstrained gait. Muscular co-activation of muscle pairs was then evaluated by extracting different co-activation indicators, and linking them with kinematic markers of motor function. The combination of disease progression and pharmacological treatment resulted in a significant decrease in terms of co-activation indexes for two pairs of agonist-antagonist muscles, and for one of these two pairs the decrease in co-activation was correlated with a decrease in the motor function of gait.

I. Introduction

Duchenne muscular dystrophy (DMD) is an X-linked muscle disease caused by an absence of the protein, dystrophin. Approximately DMD has an inherited origin in two thirds of cases, while for the remaining ones it is linked to a genetic mutation. It is characterized by a progressive muscular weakness and dystrophy that can compromise ambulatory status as well as cardiopulmonary function. The prevalence rate for DMD is around 63 per million and it affects children in the first years of life. It is generally diagnosed between the ages of 3 and 4 years by clinical observations but it must be confirmed through genetic tests [1]-[3]. The muscular disease is more proximal than distal, affects lower limbs more often than upper limbs, and is characterized more by extensor weakness than by flexor weakness [4], [5].