RESUMEN
BACKGROUND: Measurements from pressure biofeedback units (PBUs) can be used to evaluate the activity of the transversus abdominis (TrA) muscle indirectly. These measurements can classify patients or monitor the progress of treatment programmes for people with low back pain. OBJECTIVE: To systematically review studies on the measurement properties of PBUs for the assessment of TrA activity. DATA SOURCES: Eligible studies were identified through searches of PUBMED, CINAHL and BIREME (1990 to 2009). In addition, hand searches of journals and citation tracking were performed. STUDY SELECTION: Full-text studies involving any type of clinimetric tests of PBU measurement for the assessment of TrA activity were selected. DATA EXTRACTION: Two independent reviewers selected the studies, extracted the data and assessed methodological quality. DATA SYNTHESIS: Due to the heterogeneity of study designs and statistical analysis, it was not possible to pool the data for a meta-analysis. RESULTS: Six studies met the inclusion criteria. These studies were typically of low quality and recruited healthy subjects rather than patients with low back pain. The studies found moderate to good reproducibility (intra-class correlation coefficients from 0.47 to 0.82) and acceptable construct validity (intra-class correlation coefficients from 0.48 to 0.90). CONCLUSIONS: The current evidence about the measurement properties of PBUs for the assessment of TrA activity is mainly based on studies with suboptimal designs, and the findings from these studies are likely to be overly optimistic. The most important clinical questions about the measurement properties of PBUs for the assessment of TrA activity are yet to be answered.