O uso da eletromiografia para identificação de fadiga na dor lombar baixa

Resumo

A surface EMG technique is described which was developed to provide an objective measure of paraspinal muscle function in patients with LBP. The device, referred to as a Back Analysis System (BAS) records changes in spectral and amplitude parameters from 6 EMG electrodes during a series of fatiguing isometric tasks that rely on visual force-feedback. Changes in the EMG median frequency, a fatigue index, are first compared in this report for different electrode locations and different constant force levels in healthy control subjects. The results demonstrate that there is a characteristic “normal” pattern of fatigue among the various paraspinal muscle sites that is symmetric with respect to contra lateral paravertebral locations, but significantly different when comparing upper and lower lumbar levels. Changes in EMG median frequency during a sustained contraction are significantly increased with increases in force level of the contraction. In patients with chronic LBP in remission, the degree of median frequency change is significantly higher than in control subjects matched for strength. These findings are likely related to muscle deconditioning resulting from chronic disuse. Other findings are reported from BAS protocols among sub-acute LBP patients with moderate to severe disability. These patients have a distinctive asymmetrical pattern of muscle fatigue as measured by the median frequency and amplitude parameters. This pattern is interpreted as a way of measuring muscle imbalances resulting from to pain-related inhibition or avoidance behavior. Implications of these characteristic EMG findings are discussed in terms of differential treatment strategies for LBP.