Investigation of core muscle activation in patients with chronic low back pain based on the 6-item movement control...

The 6-item movement control test battery (6MCTB) can identify movement control impairment (MCI) in patients with chronic low back pain (CLBP). However, it remains unclear whether altered activation of core stabilizing muscles underlies poor test performance. This study aimed to determine whether performance on the 6MCTB (individual tests, direction-specific classification, and summation) is associated with lumbar multifidus (LM) and transversus abdominis (TrA) activation in patients with CLBP.

Forty-two patients with CLBP underwent the 6MCTB, comprising three flexion-specific tests (waiter's bow, sitting knee extension, quadruped rocking backward) and three extension-specific tests (posterior pelvic tilt, prone knee flexion, quadruped rocking forward). The LM and TrA activation were measured using rehabilitative ultrasound imaging. Independent samples t-tests were used to compare LM and TrA activation between participants with positive and negative test results across different rating approaches.

LM activation showed significantly reduced activation (P < 0.05) in patients with positive flexion-specific tests, extension-specific tests, and summation compared to those with negative results. TrA activation did not differ significantly between positive and negative groups (P > 0.05) across most tests, except prone knee flexion, which showed an unexpected increase in TrA activation in the positive group.

Based on individual tests, direction-specific classification, and summation from the 6MCTB, poorer test performance was consistently associated with reduced LM activation in patients with CLBP. However, TrA activation showed no consistent between-group differences. These findings suggest that LM dysfunction is more strongly associated with 6MCTB performance than with TrA activation in this testing context.