Abstract
BackgroundMyofascial pain is a common syndrome, which has not been studied extensively in the low back. Despite a variety of manual and instrument assisted interventions available, little work has targeted the possible effects of fast mechanical impulses on myofascial trigger points (MTrPs) on its sensitivity and electrical activity. The purpose of this experimental study was to quantify the immediate effect of one session of mechanical impulses to lumbar latent MTrPs and to normal muscle tissue with pressure pain threshold (PPT) and surface electromyography (sEMG) as outcome measures.MethodsDuring the autumn of 2009, in 41 asymptomatic subjects between 17-40 years of age the lumbar musculature was searched for a latent MTrP by a trained clinician. Using 3 disposable pre-gelled electrodes bilaterally, sEMG was recorded continuously from muscle containing either latent or no MTrP. Both the trigger point group and control group received the intervention and were blinded to group allocation. The immediate effects of mechanical impulses were assessed by sEMG and PPT before and after intervention using Wilcoxon matched-pairs signed-ranks test, Mann–Whitney U test and paired t-tests.ResultsThe PPT increased significantly across both groups (p < 0.01) after intervention. The proportionate increase (14.6 %) was comparable in both MTrP and control groups. The electrical activity on the MTrP side was not significantly higher in the MTrP group compared to the contralateral side. The decrease of resting electrical activity after intervention was significant in the MTrP group on the side of the latent MTrP (P = 0.001) as well as the contralateral side (p=0.022), and not significant in the control group on either side (p=0.33 and p=0.93).ConclusionIn this study, the immediate effect of one session of mechanical impulses was associated with a significant increase in PPT for both groups and a significant decrease in the resting electrical activity of the lumbar muscles only in the MTrP group. It is unknown if these effects have clinical significance.
Highlights
Myofascial pain is a common syndrome, which has not been studied extensively in the low back
A second aim was to investigate the effect of the presence of a latent myofascial trigger point (MTrP) on the electrical activity of the muscle involved compared to muscle tissue without latent MTrPs
The sample consisted of 25 males (61 %) with mean (SD) for age 24 (5.4) and pre-intervention pressure pain threshold (PPT) 4.5 kg/cm2 (1.5) and 16 females (39 %) with mean (SD) for age 22 (3.0) and preintervention PPT 3.7 kg/cm2 (1.2)
Summary
Myofascial pain is a common syndrome, which has not been studied extensively in the low back. Despite a variety of manual and instrument assisted interventions available, little work has targeted the possible effects of fast mechanical impulses on myofascial trigger points (MTrPs) on its sensitivity and electrical activity. The purpose of this experimental study was to quantify the immediate effect of one session of mechanical impulses to lumbar latent MTrPs and to normal muscle tissue with pressure pain threshold (PPT) and surface electromyography (sEMG) as outcome measures. MPS is commonly misdiagnosed and overlooked by clinicians who are unfamiliar with this [6] It is a complex form of neuromuscular dysfunction associated with functional deficits and broader symptomatology. Recent data suggest that neurogenic inflammation, wide dynamic range neurons and limbic system structures likely play pivotal roles in muscle sensitisation, pain chronification, somato-visceral interactions and the objective physical findings of allodynia, hyperalgesia and referred pain patterns [7]
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