Acute electromyographic responses of deep thoracic paraspinal muscles to spinal manual therapy interventions. An experimental, randomized cross-over study.

This single group, randomized, cross-over study explored whether manual therapy alters motor tone of deep thoracic back muscles by examining resting electromyographic activity (EMG) after 2 types of manual therapy and a sham control intervention. Twenty-two participants with thoracic spinal pain (15 females, 7 males, mean age 28.1 ± 6.4 years) had dual fine-wire, intramuscular electrodes inserted into deep transversospinalis muscles at a thoracic level where tissues appeared abnormal to palpation (AbP) and at 2 sites above and below normal and non-tender to palpation (NT). A surface electrode was on the contralateral paraspinal mass at the level of AbP. EMG signals were recorded for resting prone, two 3-s free neck extension efforts, two 3-s resisted maximal voluntary isometric contractions (MVIC), and resting prone before the intervention. Randomized spinal manipulation, counterstrain, or sham manipulation was delivered and EMG re-measured. Participants returned 1 and 2 weeks later for the remaining 2 treatments. Reductions in resting EMG followed counterstrain in AbP (median decrease 3.3%, P = 0.01) and NT sites (median decrease 1.0%, P = 0.05) and for the surface electrode site (median decrease 2.0%, P = 0.009). Reduction in EMG following counterstrain during free neck extension was found for the surface electrode site (median decrease 2.7%, P < 0.01). Spinal manipulation produced no change in EMG, whereas counterstrain technique produced small significant reductions in paraspinal muscle activity during prone resting and free neck extension conditions. The clinical relevance of these changes is unclear.

Resting electromyographic activity of deep thoracic transversospinalis muscles identified as abnormal with palpation.

CONTEXT: In the 1940s, osteopathic researchers suggested that paraspinal tissue abnormality was associated with spontaneous muscle activity, but few studies have since re-examined these reports. OBJECTIVE: To determine whether abnormal motor activity plays a role in deep paraspinal tissues that appear abnormal to palpation. METHODS: Using an observational study design, the PVG of participants with thoracic pain were palpated by two examiners for consensus on the most marked level of tissue abnormality. Dual fine-wire, intramuscular electrodes were inserted into the deep transversospinalis (multifidus, rotatores) muscles at the abnormal level and at two normal sites (above and below the abnormal level). Surface electrodes were placed over the erector spinae muscles adjacent to each intramuscular electrode site. Electromyography signals were recorded during initial prone resting, three maximal voluntary isometric contractions (MVIC), and a second prone resting. The area under the curve for a 2-second period was analyzed for each condition, and values were normalized and reported as a percentage of MVIC. Data were analyzed using a 2-factor repeated-measures analysis of variance. RESULTS: Twenty-five participants with mean (SD) thoracic pain of 3.3 (1.9) on a 0 to 10 visual analog pain scale completed the study protocol. There were no statistically significant differences in normalized resting activity between the three intramuscular sites (P=.25) or between the three surface sites (P=.33). Substantial variability in normalized resting activity at each of the three intramuscular sites was evident (mean [SD] percent of MVIC: abnormal 7.83 [8.76]; normal 9.47 [8.45], 6.65 [7.39]). No statistically significant differences existed in the intramuscular EMG values between the two resting baseline periods (P=.10). CONCLUSION: The lack of statistically significant differences between EMG activity at the abnormal and normal paraspinal sites suggests that factors other than muscle activity are responsible for the apparent abnormality of these tissues to palpation. Investigation of these regions for increased tissue fluid and inflammatory mediators is recommended.