The effect of heat therapy on post-dry needling soreness in the deltoid muscle of asymptomatic subjects

Abstract

Background: Myofascial Pain Syndrome is a condition characterized by the development of hyperirritable foci in muscle. Treatments include modalities such as cryotherapy, electrotherapy, ultrasound, ischeamic compression and dry-needling, the latter of which is reported to be the most effective. A side-effect of dry-needling is post-needling soreness which results from bleeding in the area of needle insertion. The application of heat as a therapy to an injured area has been reported to decrease pain by blocking nociceptors, decreasing muscle spasm, and increasing connective tissue extensibility. Objectives: To determine the relative effectiveness of heat therapy immediately after dry-needling versus dry-needling alone on post-needling soreness in the deltoid muscle of asymptomatic subjects. This was done in terms of subjective and objective clinical findings. Methodology: This study was designed as a randomised, parallel-controlled clinicaltrial. Thirty asymptomatic subjects were used. Each subject acted as their own control in that both the left and right arms of each subject were dry-needled. One of the arms received heat therapy after the dry-needling procedure while the other arm acted as a control. Algometer readings, a Numerical Pain Rating Scale-101 (NRS- 101) and a 24 Hour Pain Diary were used as assessment tools. Algometer and NRS-101 readings were taken before and after the dry-needling procedure and during the 24 hour follow up visit. Subjects used a 24 hour pain diary which was filled out at 3 hour intervals, to record the development of post-needling soreness. Independent samples t-test and Pearson’s chi square test were used to compare age and gender between the treatment groups. Repeated measures ANOVA testing was used to compare the effect of heat treatment with no heat treatment in the 60 arms over the three time periods of assessment for the outcomes which were 4 5 measured as continuous variables (NRS-101 and algometer). For binary outcomes such as the presence or absence of pain at any time point, Fisher’s exact tests were used to compare the heat treated with the control arms in the left and right arms separately. A p value of less than 0.05 was considered as statistically significant. Results: Both the objective and subjective measurements from the heat intervention and control groups revealed the development of post-needling soreness. There was a slight trend of heat therapy decreasing post-needling soreness in terms of subjective (NRS-101 and pain diary) and objective (algometer) findings which was however, not found to be statistically significant. Conclusion: Although the results of the study revealed no statistical evidence of a beneficial effect of heat therapy on objective or subjective findings clinical significance could not be excluded due to the observed trend of heat therapy decreasing post-needling soreness in terms of subjective (NRS-101 and pain diary) and objective (algometer) findings. Further investigation is recommended.