Concurrent validity of the pressure biofeedback unit and surface electromyography in measuring transversus abdominis muscle activity in patients with chronic nonspecific low back pain / Validade concorrente da unidade de biofeedback pressórico e eletromiografia de superfície na mensuração da atividade muscular do transverso abdominal em pacientes com dor lombar crônica inespecífica

BACKGROUND: The Pressure biofeedback unit (PBU) is an assessment tool used in clinical practice and research aimed to indirectly analyze the transversus abdominis (TrA) muscle activity. The concurrent validity of the PBU in a clinically relevant sample is still unclear. OBJECTIVE: The purpose of this study was to evaluate the concurrent validity and diagnostic accuracy of the PBU in measuring TrA muscle activity in patients with chronic nonspecific low back pain. METHOD: This study was performed using a validation, cross-sectional design. Fifty patients with chronic nonspecific low back pain were recruited for this study. To test the concurrent validity both PBU measures (index test) and superficial electromyographic measures (reference-standard test) were compared and collected by a physical therapist in a series of voluntary contraction maneuvers of TrA muscle. RESULTS: Participants were on average 22 years old, weighed 63.7 kilos, 1.70 meters height and mean low back pain duration was 1.9 years. It was observed a weak and non-significant Phi coefficient (r=0.2, p<0.20). With regards to diagnostic accuracy tests, our results suggest a low sensitivity (60%) and specificity (60%) of the PBU. The positive predictive value was high (0.8) and negative predictive value was low (0.2). Conclusions: Concurrent validity of the PBU in measuring TrA muscle activity in patients with chronic nonspecific low back pain is poor given the low correlation and diagnostic accuracy with superficial EMG.

CONTEXTUALIZAÇÃO: A Unidade de Biofeedback Pressórico (UBP) é uma ferramenta de avaliação usada na prática clínica e pesquisa científica para analisar indiretamente a atividade muscular do transverso abdominal (TrA). A validade concorrente da UBP em uma amostra clinicamente relevante ainda não está esclarecida. OBJETIVO: Avaliar a validade concorrente e acurácia diagnóstica da UBP em mensurar a atividade muscular do TrA em pacientes com dor lombar crônica inespecífica. MÉTODO: Este estudo foi realizado usando um delineamento de validação. Cinquenta pacientes com dor lombar crônica inespecífica foram recrutados. Para testar a validade concorrente, ambas as medidas pressóricas (teste índice) e eletromiográficas superficiais (teste padrão de referência) foram comparadas e coletadas por um fisioterapeuta a partir de uma manobra de contração voluntária do músculo TrA. RESULTADOS: Os participantes tinham em média 22 anos, 63,7 kg, 1,70 m de altura, e a duração média de dor lombar era de 1,9 ano. Observou-se um coeficiente Phi fraco e não significativo (r=0,2; p<0,20). Com relação aos testes de acurácia diagnóstica, os resultados sugerem uma baixa sensibilidade (60%) e especificidade (60%) da UBP. O valor preditivo positivo foi elevado (0,8), e o valor preditivo negativo foi baixo (0,2). Conclusões: A validade concorrente da UBP em mensurar a atividade muscular do TrA em pacientes com dor lombar crônica inespecífica é pobre, considerando a baixa correlação e acurácia diagnóstica com a EMG de superfície.

Segmental stabilization and muscular strengthening in chronic low back pain: a comparative study

OBJECTIVE: To contrast the efficacy of two exercise programs, segmental stabilization and strengthening of abdominal and trunk muscles, on pain, functional disability, and activation of the transversus abdominis muscle (TrA), in individuals with chronic low back pain. DESIGN: Our sample consisted of 30 individuals, randomly assigned to one of two treatment groups: segmental stabilization, where exercises focused on the TrA and lumbar multifidus muscles, and superficial strengthening, where exercises focused on the rectus abdominis, abdominus obliquus internus, abdominus obliquus externus, and erector spinae. Groups were examined to discovere whether the exercises created contrasts regarding pain (visual analogical scale and McGill pain questionnaire), functional disability (Oswestry disability questionnaire), and TrA muscle activation capacity (Pressure Biofeedback Unit = PBU). The program lasted 6 weeks, and 30-minute sessions occurred twice a week. Analysis of variance was used for inter- and intra-group comparisons. The significance level was established at 5 percent. RESULTS: As compared to baseline, both treatments were effective in relieving pain and improving disability (p<0.001). Those in the segmental stabilization group had significant gains for all variables when compared to the ST group (p<0.001), including TrA activation, where relative gains were 48.3 percent and -5.1 percent, respectively. CONCLUSION: Both techniques lessened pain and reduced disability. Segmental stabilization is superior to superficial strengthening for all variables. Superficial strengthening does not improve TrA activation capacity.