Subjective and objective evaluation of shoulder muscle fatigue

Abstract

In order to relate EMG signs of localized muscle fatigue to subjectively perceived muscle fatigue, a study was undertaken on 20 healthy volunteers exposing their right trapezius muscle by raising the arm to 90 degrees of abduction. Every person performed two contractions: 0 kg hand load during 5 min and 2 kg hand load during 2.5 min. Surface EMG was recorded and analysed with respect to RMS amplitude and mean power frequency (MPF). Subjective muscle fatigue was estimated with a psychophysical rating scale (Borg's CR-10 Scale). At high load level we found a significant correlation between MPF and the CR-scores (r = -0.46), but at low load level there was no correlation. At high load level there was a linear decrease of MPF with increasing load dose, but at low load level the MPF did not change, despite significant subjective fatigue. There was a linear rise of the CR-score with increasing load dose, more pronounced at high load level. It was concluded, that at low load levels common in working life, MPF and subjective scores seem to provide different fatigue information. Moreover, the MPF did not seem to work as a valid estimator of muscle fatigue at this low load level. Caution is recommended if it is to be used in static low-load situations.

Neck Disorders among Construction Workers: Understanding the Physical Loads on the Cervical Spine during Static Lifting Tasks

“…For the posterior neck muscles (upper trapezius muscle) along C4 as well as C7 levels, at all the neck postures, a significant weight-muscle activation relationship was observed. This observed increase in the activation of the upper trapezius muscle along the C7 level with the increase in the weight at the shoulder height is consistent with previous investigations 7,15,28,29) .…”

Occupational Safety and Health Aspects of Voice and Speech Professions

“…Female subjects had higher symptom scores for all factors in dry conditions, supporting the interpretation that the changes in parameter values are related to fatigue (more effort needed) [10].…”

“…For instance, a study of shoulder muscle fatigue revealed that light and heavy loading both caused subjectively perceived fatigue, but at the physiological level, only heavy loading resulted in electromyographically detectable signs of loss of muscular power [10]. The discovery of objective correlates for subjective voice complaints and fatigue would be highly desirable, as they could be used to substantiate voice problems as a hitherto neglected aspect of OSH.…”

Normalised Mutual Information of High-Density Surface Electromyography during Muscle Fatigue

“…There are many studies that have analysed changes in the fundamental spectral and time domain features of the sEMG, such as the median frequency or the root mean square [1,13]. However, these approaches have been found to be unreliable since many other factors can have a significant effect on them [14].…”

“…However, techniques that rely on measuring the changes in sEMG amplitude or the frequency spectrum, which are aggregate measures, can potentially be misleading [14]. Introducing higher resolution spatial information does not minimise the inherent shortcomings of these techniques.…”