Objective: Objectives of this study were to (1) quantify the immediate effect of Nimmo technique on muscle elasticity, pain perception, and disability and (2) evaluate comparative effectiveness of treating all primary and secondary trigger points (TrPs) vs primary TrP only. Methods: Fourteen chronic low back pain subjects recruited from a chiropractic college were tested in this within-day repeated-measures design study. Gluteus medius containing a prominent TrP was indented for 4 sessions using a mechanoacoustic indentor system. A finite element optimization method extracted hyperelastic material constants of the gluteus medius. Load-deformation response on a standardized block was simulated. Area under the load-deformation curve from 0% to 25% deformation (A FE) and force at 25% deformation (F FE) were determined. No treatment was applied between the first and second sessions. Only the primary TrP in gluteus medius was treated between the second and third sessions. Full Nimmo treatment was used between the third and fourth sessions requiring treatment of all primary and secondary TrPs. The A FE, F FE, tissue thickness, subjective pain, and Oswestry Disability Index were compared between sessions. Results: After full Nimmo treatment, A FE and F FE were significantly smaller than baseline (P =.021 and.027, respectively) and focal TrP treatment only (P =.003 and.001, respectively). The changes accompanied concomitant improvement in subjective pain and disability. It appears that focal TrP treatment resolves TrP, but full Nimmo treatment further reduces electrogenic spasm. Conclusions: Immediate effect of a single full Nimmo treatment appears to reduce muscle tone, subjective pain, and disability and be more beneficial than focal TrP treatment. ; Department of Health Technology and Informatics