Comparison of spectral and entropic measures for surface electromyography time series: A pilot study

Abstract

Abstract-In a previous study, we reported that the mean square displacement calculated from the surface electromyography (sEMG) signal of low back muscles exhibits a plateaulike behavior for intermediate times 20 ms < t < 400 ms. This property indicates the existence of correlations in the signal for times much longer than the inverse of the median frequency (MF), which is calculated from the power spectrum 1/<f > = 1/(100 Hz) = 10 ms, where <f > is the MF. This result suggests the use of methods from nonlinear analysis to characterize sEMG time series. In this study, we applied these techniques to sEMG signals and calculated the time-dependent entropy. The results showed that the entropy of physiological time series from nondisabled control subjects is higher than the entropy from subjects with low back pain (LBP). The entropy reveals properties of the sEMG signal that are not captured by the power spectrum. In turn, this suggests a possible benefit of entropy as a tool for the clinical assessment of LBP. Because the two groups of subjects were not matched by age, the physiological origin of the observed differences between groups could be attributed to either LBP, age, or both. Additional studies with larger sample sizes and age-matched subjects are needed to investigate the relationship between LBP and entropy.

Spectral and entropy changes for back muscle fatigability following spinal stabilization exercises

“…Our previous study indicated that control subjects revealed significantly larger entropy levels of the EMG signals than subjects with LBP [3]. Thus, the results of the current study consistently demonstrated a connection between physiological "health" and complexity [4,13].…”

“…This plateau value of S t was referred to as the entropy. The detailed entropy calculation process is fully described in previous studies [1][2][3]. Our previous data were partially used in this study in order to monitor the effects of the exercise intervention.…”

“…Several studies have reported that entropic measures for surface electromyography (EMG) time series are useful for evaluating localized muscular fatigue in a noninvasive fashion [1][2][3][4][5]. A previous study confirmed that the entropy measurement for characterizing neuromuscular alterations is reliable [6].…”

“…This connection might prove useful in a clinical assessment of LBP. It is important to understand that Costa et al and Chialvo argued that pathology and/or dysfunction is associated with less variability [1][2][3]. Generally, biological time series are complex data that need to be distilled to useful application to assess a pathology and/or dysfunction.…”

Fatores do trabalho associados à lombalgia não específica, caracterizada no âmbito da resistência da musculatura extensora lombar, entre trabalhadores de enfermagem de Unidades de Terapia Intensiva

“…Ademais, há de se ressaltar que estudos recentes têm indicado que a musculatura lombar possui uma função importante na identificação de grupos lombálgicos (SUNG; ZURCHER; KAUFMAN, 2007;HEYDARI et al, 2010).…”