Spinal manipulative procedures have been claimed to alter resting electromyographic activity (EMG) of paraspinal muscles, but the evidence is inconsistent. This study examined the effect of two osteopathic techniques, high-velocity low-amplitude (HVLA) thrust and counterstrain (CS), on resting EMG of the deep thoracic paraspinal muscles in regions that appear abnormal to palpation.This randomized controlled crossover study was conducted using 3 treatments, HVLA, CS, and sham laser control, with a 1-week washout between. Dual fine-wire, intramuscular electrodes were inserted into the deep transversospinalis muscles at a thoracic level where the tissues appeared abnormal and tender to palpation (AbP), and at two normal sites superior and inferior to the AbP. Surface electrodes were placed over the erector spinae muscles adjacent to the AbP site. During the following conditions, pre- and post-treatment EMG signals were recorded while subjects were prone: 1. Resting before and after other conditions (baseline); 2. Two 3-s free neck extension tasks (EXT, a sub-maximal functional task); 3. Two 3-s resisted maximal voluntary isometric contractions (MVIC).Two second periods from each condition were processed and the mean amplitude (uV) was normalized to the highest pre-treatment MVIC reading. EMG scores for normal sites were averaged (NTav). Wilcoxon signed ranks tests were used to test whether the normalized baseline scores changed from pre- to post-treatment. Friedman tests were used to determine whether the change in muscle activity from pre- to post-treatment differed between treatments.Twenty-two participants were recruited [15 females and 7 males, mean age of 28.1-years (SD = 6.4), mean BMI of 23.8 kg.m −2 (SD = 6.4)]. Mean current pain intensity was 3.2 out of 10 (SD = 1.1). A significant reduction in baseline EMG was found following the CS treatment in the AbP (median decrease 3.3%; p = 0.01, d = 0.33), NTav (median decrease 1.0%; p = 0.05, d = 0.024), and surface (median decrease 2.0%; p = 0.009, d = 0.29) sites. A significant reduction in surface EMG following CS treatment during EXT was also found (median decrease 2.7%; p = 0.003, d = 0.20). EMG activity from other sites and following other treatments was not significantly changed. There was a significant between-group difference in baseline activity for the surface site (p = 0.02, d = 0.58); the change for the CS treatment (median decrease 2.0%) was larger than the change for the HVLA treatment (median increase 0.6%). There were no other significant differences between the treatments.CS appeared to produce small significant reductions in paraspinal muscle activity during resting and free neck extension conditions, whereas the other treatments produced no change. However, given the very small reductions produced, clinical relevance of these changes is unclear.