The Relationship of Leg Muscle Function and Fatigue During Walking in Spinal Muscular Atrophy
By: Jacqueline Montes
Published: 10/17/2012
Uploaded: 12/07/2017
Uploaded by: Pocket Masters
Pockets: 2012 (October) Teachers College Columbia University Ed.D. Dissertations, Gottesman Libraries Archive, Historical Dissertations
Tags: Fatigue, outcome measure, six minute walk test, splinal muscular atrophy, weakness

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Description/Abstract: Spinal Muscular Atrophy (SMA) is a genetically determined motor neuron disease that typically presents in infancy or childhood and results in progressive muscle weakness of proximal more than distal muscles and most of the lower limbs in the mildest phenotype. Fatigue is another prominent symptom of SMA but there are few measures that objectively quantify it. The primary objective of this study was to determine the association between muscle weakness, function, and fatigue. Better understanding of the precise relationships between muscle function and fatigue-related changes will direct future rehabilitation strategies and identify potential targets for treatment. In this cross-sectional study of 10 ambulatory SMA patients, participants performed the Six Minute Walk Test (6MWT) with spatiotemporal analysis of gait and surface electromyography (EMG) from 4 muscle groups in the right leg. Two measures of muscle activity, the average mean power frequency (MPF) and root mean square amplitude (RMS), were calculated from the EMG signal of the anterior tibialis, gastrocnemius, rectus femoris, and biceps femoris muscles. The gait measures of stride length and velocity were obtained from a computerized gait mat in the first and last minutes of the 6MWT. Strength was measured using standardized manual muscle testing and quantitative strength assessments on most leg muscle groups. As predicted, there were significant decreases in RMS, stride length and velocity during the 6MWT. However, the MPF did not change. Consistent with previous findings in patients with SMA there was a centripetal pattern of weakness with the hip musculature being the weakest muscle group. Notably, the strength of the knee flexors and hip abductors was associated with fatigue-related changes and overall leg strength was associated with 6MWT distance. From this study, we have demonstrated that we can quantify fatigue in SMA using clinical assessments, spatiotemporal analysis of gait, and EMG analysis. We found an inverse relationship of MPF to RMS amplitude which may be reflective of the SMA muscle pathophysiology. For clinical trial design, these methods could be incorporated as outcome measures of function and fatigue and total leg strength could be used to stratify patients and identify those most susceptible to losing functional ambulation.