Immediate changes in lumbar multifidus thickness during faradic and interferential current stimulation in recurrent low back pain: a randomized crossover pilot study

Introduction Neuromuscular electrical stimulation has been widely used to stimulate muscles. Although faradic current (FRD) is commonly used, it may not be suitable for lumbar multifidus activation. Interferential current (IFC) may reduce skin impedance and improve current delivery to the lumbar multifidus muscle. The aim of this study was to explore the lumbar multifidus response to different electrical currents. Methods Five participants (age = 24.0, SD = 3.9) with recurrent low back pain (rLBP) and at least two episodes in the past 3 months that interfered with activities of daily living or required treatment, and five age, sex, and BMI-matched healthy controls (HC; age = 23.0, SD = 2.5) were recruited. FRD and IFC were each applied once per side using a continuous incremental protocol from levels of discomfort (LOD 0–10); no repeated series, repetitions, or fixed on/off duty cycle were used. Ultrasound imaging was used to measure the percent change in lumbar multifidus thickness (primary outcome) at rest and across LOD 0–10. Normality and homogeneity of variances were assessed, and no violations were found. A three-way mixed ANOVA was used to examine the interaction between groups and within-groups (currents) and LOD (0–10), with Greenhouse-Geisser corrections. Post-hoc Bonferroni was also performed. Results A significant interaction was found (p = 0.023; partial n2 = 0.36). In the rLBP group, IFC elicited greater LM thickness change than FRD from LOD 3–10 with large effects (Cohen’s dz = 1.06–2.08), reaching 22.35(12.18)% vs. 7.08(1.83)% at LOD 10. Between-group differences under IFC were significant at LOD 3–8 with large effects (Cohen’s d = 1.72–2.92), with 20.45(13.00)% in rLBP vs. 4.16(2.79)% in HC at LOD 7. Conclusions IFC elicited greater immediate lumbar multifidus thickness change than FRD in participants with rLBP. These pilot findings reflect single-session ultrasound-based responses and do not establish clinical or long-term rehabilitation effectiveness.