Lumbar multifidus muscle thickness does not predict patients with low back pain who improve with trunk stabilization exercises

Objective: To understand lumbar multifidus (LM) muscle activation as a clinical feature to predict patients with low back pain (LBP) who are likely to benefit from stabilization (STB) exercises.

Design: Prospective, cohort study.

Setting: Outpatient physical therapy clinics.

Participants: Persons with LBP were recruited for this study. Subjects (N=25) were classified as either eligible to receive STB exercises or ineligible on the basis of current clinical prediction rules.

Interventions: Six weeks of STB treatment.

Main outcome measures: Before and after treatment, subjects underwent rehabilitative ultrasound imaging to quantify LM-muscle activation and completed disability and pain questionnaires. Analyses were performed to examine the (1) relation between LM-muscle activation and current clinical features used to predict patients with LBP likely to benefit from STB exercises, (2) LM-muscle activation between the STB-eligible and STB-ineligible groups before and after STB treatment, and (3) relation between LM-muscle activation before STB treatment and (a) disability and (b) pain outcomes after treatment for both groups.

Results: No relation was found between LM-muscle activation and the number of clinical features. Before STB treatment, LM-muscle activation between the STB-eligible and STB-ineligible groups did not differ. After STB treatment, LM-muscle activation differed between the groups; however, this interaction was because the LM-muscle activation for the STB-eligible group decreased after treatment while that for the STB-ineligible group increased after treatment. Finally, only the STB-eligible group had a significant reduction in disability following treatment; however, no relation was found between LM-muscle activation before treatment and (a) disability or (b) pain outcomes after treatment in the STB-eligible group.

Conclusions: LM-muscle activation does not appear to be a clinical feature that predicts patients with LBP likely to benefit from STB exercises.