Effects of muscle fatigue on postural control in people with multiple sclerosis

Abstract

Multiple sclerosis (MS) is a lifelong inflammatory disease of the central nervous system that leads to demyelination and axonal loss resulting in sustained disability over time. It is estimated that MS affects more than 2.3 million young adults between 20 and 40 years. Postural control is one of the most affected aspects of this population. Furthermore, more than 80% of people with MS report fatigue symptoms. However, it is little known about the effect of muscle fatigue on the control of people with MS. Knowing the effects of muscle fatigue on postural control is important to enabling more specific interventions for this population. Thus, the purpose of this study is to investigate the influence of muscle fatigue on the postural control of people with MS and compare it with neurologically healthy individuals. Thirty adults, aged between 18 and 55 years old, 15 individuals with MS and 15 neurologically healthy adults will participate in the study. Participants will perform postural and muscle strength assessment before and after ankle muscle fatigue. The participants will perform 3 trials of 60s of postural control in the condition of eye fixation and saccadic movement. Induction of muscle fatigue will be performed in a task of plantar flexion and dorsiflexion of the ankle on a step, with the controlled frequency of movement. The following parameters of the center of pressure (CoP) will be measured before and after muscle fatigue: CoP displacement, area of CoP, mean velocity of the CoP, root mean square of the displacement of CoP, median frequency, predominant frequency and 95 % of total frequency. The parameters of interest will be analyzed by means of MANOVAs with factor for group, condition, and muscular fatigue, with repeated measures for the last two factors.