Effect of a single session of muscle-biased therapy on pain sensitivity: a systematic review and meta-analysis of randomized controlled trials

Abstract

Background: Muscle-biased therapies (MBT) are commonly used to treat pain, yet several reviews suggest evidence for the clinical effectiveness of these therapies is lacking. Inadequate treatment parameters have been suggested to account for inconsistent effects across studies. Pain sensitivity may serve as an intermediate physiologic endpoint helping to establish optimal MBT treatment parameters. The purpose of this review was to summarize the current literature investigating the short-term effect of a single dose of MBT on pain sensitivity in both healthy and clinical populations, with particular attention to specific MBT parameters of intensity and duration.

Methods: A systematic search for articles meeting our prespecified criteria was conducted using Cumulative Index to Nursing and Allied Health Literature (CINAHL) and MEDLINE from the inception of each database until July 2012, in accordance with guidelines from the Preferred Reporting Items for Systematic reviews and Meta-Analysis. Relevant characteristics from studies included type, intensity, and duration of MBT and whether short-term changes in pain sensitivity and clinical pain were noted with MBT application. Study results were pooled using a random-effects model to estimate the overall effect size of a single dose of MBT on pain sensitivity as well as the effect of MBT, dependent on comparison group and population type.

Results: Reports from 24 randomized controlled trials (23 articles) were included, representing 36 MBT treatment arms and 29 comparative groups, where 10 groups received active agents, 11 received sham/inert treatments, and eight received no treatment. MBT demonstrated a favorable and consistent ability to modulate pain sensitivity. Short-term modulation of pain sensitivity was associated with short-term beneficial effects on clinical pain. Intensity of MBT, but not duration, was linked with change in pain sensitivity. A meta-analysis was conducted on 17 studies that assessed the effect of MBT on pressure pain thresholds. The results suggest that MBT had a favorable effect on pressure pain thresholds when compared with no-treatment and sham/inert groups, and effects comparable with those of other active treatments.

Conclusion: The evidence supports the use of pain sensitivity measures by future research to help elucidate optimal therapeutic parameters for MBT as an intermediate physiologic marker.

Keywords: muscle-biased therapy; pain sensitivity; pressure pain threshold.

Figure 1

Flow chart of study identification, selection, and inclusion. Abbreviation: CINAHL, Cumulative Index to Nursing and Allied Health Literature.

Figure 2

Forest plot depicting overall effect of MBT across all studies and subgroup effect of MBT based on type of comparison group. Notes: Open diamond depicts overall effect size across all studies. Colored diamonds depict subgroup effect size based on type of comparison group. For example, top colored diamond is effect size for MBT studies with active comparison groups. The width of diamond corresponds to its 95% CI (listed in figure). Individual study effect sizes (and 95% CI) are depicted with boxes (whiskers). Box and whisker size and thickness for each individual study illustrate the weighted contribution of that study to the overall effect size (eg, larger boxes/thicker lines contribute more to overall effect size). ^aActive comparison; ^bsham comparison; ^ccontrol comparison; ^dMBT arm received superficial pressure; ^eMBT arm received deep pressure; ^fMBT arm received ischemic compression; ^gMBT arm received trigger point therapy. Abbreviations: CI, confidence interval; MBT, muscle-biased therapy.

Figure 3

Forest plot depicting subgroup effect of MBT based on type of sample population. Notes: Open diamond depicts overall effect size across all studies included in this subgroup analysis. Colored diamonds depict subgroup effect size based on type of comparison group. For example, top colored diamond is effect size for MBT studies with clinical samples. The width of diamond corresponds to its 95% CI (listed in figure). Individual study effect sizes (and 95% CI) are depicted with boxes (whiskers). Box and whisker size and thickness for each individual study illustrate the weighted contribution of that study to the overall effect size (eg, larger boxes/thicker lines contribute more to overall effect size). ^aSham comparison; ^bcontrol comparison; ^cactive comparison. Abbreviations: CI, confidence interval; MBT, muscle-biased therapy.