Are changes in pain induced by myofeedback training related to changes in muscle activation patterns in patients with work-related myalgia?

Abstract

The objective of this explorative study was to investigate to what extent changes in perceived pain, induced by myofeedback training, are correlated to changes in muscle activation patterns. Thirty subjects with work-related myalgia received myofeedback training. Before (T(0)), directly after (T(1)) and 4 weeks or, in a subset of patients, 3 months after (T(2)) this training, surface electromyography (sEMG) measurements of the upper trapezius muscle were performed during standardized computer tasks; a typing and a stress task. Besides this, visual analogue scales (VAS) were filled in to assess the levels of pain in the neck and shoulders. From the sEMG, root mean square (RMS) and relative rest time (RRT, i.e. the percentage of time RMS is below a certain threshold) were used for data analysis. The relationships between RRT, RMS and VAS at T(0) as well as for the changes between T(1)-T(0) and T(2)-T(0) were investigated using Spearman correlation coefficients. The results revealed no significant correlations between VAS and RMS both at baseline (range R = -0.22 to 0.17) and for the observed changes (range R = -0.33 to 0.32). Also, for VAS and RRT, low correlations were found for baseline (range R = -0.27 to 0.21) and for changes between T(1)-T(0) (range R = -0.02 to 0.38). However, for the changes between T(2)-T(0), correlation coefficients for the VAS for the shoulder and the RRT of the right trapezius during both the typing and stress tasks were significant at the P = 0.05 level, whereas the correlation coefficients for the VAS for the neck and both the left and right trapezii during the stress task approached significance (P = 0.05 and P = 0.1, respectively). These results suggest that decreases in pain observed at long term follow up after myofeedback training might occur as a result of an increased ability to relax but not as a result of decreased muscle activation level. However, the largest correlation found was 0.6. This means that the maximal explained variance (R (2)) is low (36%), and that there are also other processes than the changes in muscle activation that contribute to changes in perceived pain.

The influence of biofeedback training on trapezius activity and rest during occupational computer work: a randomized controlled trial

“…The studies evaluating eVects of biofeedback training on muscle activity and pain intensity of the neck and shoulder region have provided bilateral biofeedback of trapezius activity (Faucett et al 2002;Hermens and Hutten 2002;Voerman et al 2006Voerman et al , 2007Vollenbroek-Hutten et al 2006). However, unilateral biofeedback may potentially cause bilateral reductions in trapezius activity due to the close neural connections and bilateral activation of the homologous trapezius muscles (Alexander et al 2007;Alexander and Harrison 2002).…”

“…A few studies have investigated eVects of biofeedback training on computer workers (Hermens and Hutten 2002;Voerman et al 2007;Vollenbroek-Hutten et al 2006). However, since the trapezius activity during computer work in laboratory and occupational settings may diVer (Blangsted et al 2004;Mork and Westgaard 2006) and randomized controlled trials evaluating eVects of biofeedback training on computer workers during their normal work are lacking, the eVectiveness of biofeedback training as a mean to reduce trapezius activity in computer workers remains uncertain.…”

Biofeedback effectiveness to reduce upper limb muscle activity during computer work is muscle specific and time pressure dependent

“…Auditory biofeedback presented to subjects performing a gross-motor task, showed an increase in the relative rest time and a decrease in muscle activity (Voerman et al, 2004). Vollenbroek-Hutten et al (2006) showed significant changes in muscle activation pattern after biofeedback training (Voerman et al, 2007;Vollenbroek-Hutten et al, 2006). Biofeedback in the aforementioned studies was given similar to that in the present study, i.e.…”

“…auditory (Gerard et al, 2002), visually (Palmerud et al, 1995), and vibratory signal (de Korte et al, 2008;Vollenbroek-Hutten et al, 2006). However, previous studies have not demonstrated one mode being more effective than the other with regard to reducing muscle activity.…”

Repetitive and Monotonous Work Among Women: Psychophysiological and Subjective Stress Reactions, Muscle Activity and Neck and Shoulder Pain

“…This apparent inability to relax the trapezius muscle during leisure time among pain-afflicted workers was also found during sleep in a separate analysis (Mork & Westgaard, 2004). Moreover, a study concerning myofeedback training in individuals with work-related myalgia in the neck and shoulders showed that a reduction in pain was not related to a decreased muscle activity level, however, it was related to an increased ability to relax the muscles (VollenbroekHutten, Hermans, Voerman, Sandsjö & Kadefors, 2006). Thus, there seems to be growing evidence that sustained low-level muscle activity and lack of muscle rest are risk factors for muscle pain in the neck and shoulder region, thus supporting the Cinderella hypothesis.…”