Abstract
INTRODUCTION: Muscle weakness is the most prominent impairment in Duchenne muscular dystrophy (DMD) and often involves the loss of functional ability as well as other limitations related to daily living. Thus, there is a need to maintain muscle strength in large muscle groups, such as the femoral quadriceps, which is responsible for diverse functional abilities. However, the load and duration of training for such rehabilitation has proven to be a great unknown, mainly due to the undesired appearance of muscle fatigue, which is a severe factor for the injury of muscle fibers. OBJECTIVES: The aim of the present study was to determine a fatigue index by means of surface electromyography (EMG) for the parameterization of muscle strengthening physiotherapy training. METHODS: A cross-sectional study (case series) was carried out involving four patients with DMD. Three pairs of surface electrodes were placed on the motor point of the Rectus femoris, Vastus lateralis and Vastus medialis of the dominant limb, maintaining the knee at 60º of flexion. The participants were instructed to perform the extension movement of this joint at four strength levels (100%, 80%, 60% and 40% of maximal voluntary isometric contraction). RESULTS: The slope of the linear regression line was used for the determination of the fatigue index, performed by Pearson's test on the median frequency of each strength level. CONCLUSION: Electromyographic measurements of the strength index for muscle training proved to be a simple accessible assessment method, as well as an extremely valuable tool, allowing the design of a muscle strength training program with an individualized load threshold.
Highlights
Muscle weakness is the most prominent impairment in Duchenne muscular dystrophy (DMD) and often involves the loss of functional ability as well as other limitations related to daily living
Considering the importance of these muscles in activities that affect the independence of patients with DMD, the aim of the present study was to determine a fatigue index by means of surface electromyography (EMG) that can serve as parameterization for physiotherapy training
The three pairs of surface electrodes were placed on the motor point of the Rectus femoris (RF), Vastus lateralis (VL) and Vastus medialis (VM), muscles of the dominant limb following the longitudinal direction of the muscle fibers [16, 17]
Summary
Muscle weakness is the most prominent impairment in Duchenne muscular dystrophy (DMD) and often involves the loss of functional ability as well as other limitations related to daily living. In children in whom there has been an early identification because of a family history, the Gowers’ sign (compensatory maneuver when standing up from the ground, in which the patient uses his/her hands to climb up the lower limbs due to a lack of muscle strength in the thighs and hips) may be evident by 15 months of age. Most children with DMD are not identified until reaching three to five years of age Beginning at this age, there is notable muscle weakness that selectively affects the proximal muscles before the distal muscles and the lower limbs before the upper limbs [2, 3]. With the progression of the disease, there is increasing difficulty in walking, which generally becomes impossible between 8 and 12 years of age [4, 5]
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