Determination of muscle fatigue index for strength training in patients with Duchenne dystrophy

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.

Retracted: ‘The effects of Duchenne muscular dystrophy on the performance of the stomatognathic system: case–control study’, by Ferreira B., Da Silva G.P., Gonçalves C.R., et al.

“…In individuals with DMD, an associated loss of muscle strength and irregular performance of the masticatory muscles may promote a change in the position of the teeth of the dental arcade, causing a decreasing width of the palate, the development of a cross-bite, and changes in the positioning of the tongue and head. 27,40 According to Botteron et al 17 and Ueki et al 27 a comparison in the muscle strength of healthy individuals and individuals with DMD demonstrates this reduction in force in all conditions of evaluation. These results were also observed here, as the maximal molar bite force of the Duchenne group was lower than the control group.…”

“…This corroborates the study of Knaflitz et al,39 who demonstrated that fatigue is associated with individuals suffering from muscular dystrophy. Oliveira et al 40 reported that an increase in energy expenditure can compensate for a loss of muscle tissue, causing early fatigue. According to Gianola et al, 36 muscle weakness in individuals with muscular dystrophy is related to overwork, the muscle cell system has thus deleterious effects on disease progression.…”

O Uso das Escalas Funcionais para Avaliação Clínica da Distrofia Muscular de Duchenne

“…É possível a visualização precoce -até os 15 meses -do sinal de Gowers, manobra compensatória na qual a criança passa do solo para o ortostatismo "escalando" seu próprio corpo 4,6 . Porém, o mais comum é que sejam evidenciadas as manifestações clínicas por volta dos 3 anos de idade, sendo sua principal característica a fraqueza muscular progressiva, iniciando-se pelos músculos proximais dos membros inferiores, ocasionando dificuldades de locomoção e possíveis quedas, além de complicações para transferências entre localidades 2,4 .…”

“…Esta situação favorece a obesidade, prejuízo na função dos membros superiores e escoliose -que pode surgir neste momento ou agravar-se quando prévia -gerada pela fraqueza muscular. Esses dois fatores quando juntos acarretam em um comprometimento respiratório e, posteriormente, cardíaco, o que agrava ainda mais o prognóstico da doença 2,4,8 . O tratamento da DMD é paliativo.…”

Análise comparativa da força, potência e fadiga muscular de crianças e adolescentes saudáveis e com mielomeningocele

“…O treinamento muscular pode promover benefícios no desempenho motor (BEHRINGER et al, 2011), na adequação da composição corporal de crianças com sobrepeso ou obesidade (McGUIGAN et al, 2009), na melhora em relação à autopercepção sobre a imagem corporal (LUBANS, AGUIAR, CALLISTER, 2010), diminuir riscos cardiovasculares e de lesões, promover melhora no bem-estar psicossocial (FAIGENBAUM et al, 2008), aumentar o tamanho do músculo, a força e a resistência em indivíduos saudáveis (ANSVED, 2001) e ainda, poderia opor-se a deterioração secundária de tecido muscular e à perda de habilidades funcionais, como resultado de desuso (JANSEN et al, 2010). Estes temas têm sido discutidos em pacientes com disfunções periféricas como doenças neuromusculares e espinha bífida (LINDEMAN et al, 1999;OLIVEIRA et al, 2010).…”