Objective: The purpose of this study was to investigate changes in resting and/or contraction thickness of the transversus abdominis (TrA) muscle after dry needling (DN) of the lumbar multifidus (LM) in asymptomatic participants.

Methods: A randomized controlled laboratory trial with crossover design was performed. Forty-seven healthy individuals who had not experienced low back pain in the previous 6 months were randomly assigned to receive DN to the LM or a sham-DN intervention. Participants received both interventions separated at least 7 days apart. They were instructed on how to perform a concentric contraction of TrA. Resting and contraction thicknesses of the TrA were obtained through real-time ultrasound measurements before and immediately after each intervention by an assessor blinded to the intervention received. Data from 4 individuals had to be excluded because of poor image quality.

Results: Two-way analysis of variance revealed a significant contraction with treatment interaction (F_[1,42] = 11.489; P = .002). Simple main effects using paired-samples t tests and a Bonferroni post hoc analysis revealed differences in contracted states of the TrA for DN vs sham-DN (P = .009) and between contracted and resting states for the DN group (P = .001): after DN, TrA thickness at rest exhibited a mean decrease of 0.03 cm and a mean increase of 0.05 cm during contraction.

Conclusion: This study suggests that application of DN to LM was accompanied by a decreased resting thickness and an increased contraction thickness of the TrA in asymptomatic participants.

Author keywords: Abdominal Muscles; Analysis of Variance; Back Muscles; Humans; Low Back Pain; Lumbosacral Region; Paraspinal Muscles

Author affiliations: University of Nevada Las Vegas. Department of Physical Therapy (United States / Nevada / Las Vegas); Universidad Rey Juan Carlos. Department of Physical Therapy, Occupational Therapy, Rehabilitation and Physical Medicine (Spain / Alcorcón / Madrid)

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