Reproducibility of the pressure biofeedback unit in measuring transversus abdominis muscle activity in patients with chronic nonspecific low back pain

SummaryThe Pressure Biofeedback Unit (PBU) is often used by clinicians and researchers to indirectly evaluate transversus abdominis (TrA) muscle activity. The purpose of this study was to evaluate the inter and intra-examiner reproducibility of the PBU in measuring TrA muscle activity in fifty patients with chronic nonspecific low back pain. This study was performed using a test-retest design with a seven day interval. An Intraclass Correlation Coefficient (ICC2,1) of 0.74 (95% CI 0.54 to 0.85) and 0.76 (95% CI 0.58 to 0.86) was observed for the intra and inter-examiner reproducibility, respectively. The intra-examiner agreement (Limits of Agreement - LOA = 2.1 to −1.8 mmHg) and the inter-examiner agreement (LOA = 2.0 to −1.9 mmHg) were within the limits of agreement on 95% of occasions. The reproducibility of PBU in measuring TrA muscle activity in patients with chronic nonspecific low back pain ranged from satisfactory to excellent.