PREVENTION & REHABILITATION: RELIABILITY STUDY Reproducibility of the pressure biofeedback unit in measuring transversus abdominis muscle activity in patients with chronic nonspecific low back pain Pedro Olavo de Paula Lima, Ms a,b, *, Rodrigo Ribeiro de Oliveira, Ms a,b , Alberto Galva ˜o de Moura Filho, PhD c , Maria Cristina Falca ˜o Raposo, PhD d , Leonardo Oliveira Pena Costa, PhD e,f , Glo ´ria Elizabeth Carneiro Laurentino, PhD c a Department of Physiotherapy, Universidade Federal do Ceara´, Brazil b Master’s Program in Physiotherapy, Universidade Federal de Pernambuco, Brazil c Department of Physiotherapy, Universidade Federal de Pernambuco, Brazil d Department of Statistics, Universidade Federal de Pernambuco, Brazil e Master’s Program in Physiotherapy, Universidade Cidade de Sa˜o Paulo, Brazil f Musculoskeletal Division, The George Institute for Global Health, Australia Received 21 February 2011; received in revised form 6 June 2011; accepted 10 June 2011 KEYWORDS Pressure biofeedback unit; Transversus abdominis muscle; Reproducibility; Reliability; Agreement Summary The 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 per- formed using a test-retest design with a seven day interval. An Intraclass Correlation Coeffi- cient (ICC 2,1 ) 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 Z 2.1 to 1.8 mmHg) and the inter-examiner agreement (LOA Z 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. ª 2011 Elsevier Ltd. All rights reserved. * Corresponding author. Laborato ´rio de Cinesiologia e Avaliac ¸a ˜o Funcional, Rua Anibal Fernandes s/n, Recife, PE 50740-560, Brazil. Tel.: þ55 81 21268811; fax: þ55 81 21268491. E-mail address: pedrolima@ufc.br (P.O.deP. Lima). available at www.sciencedirect.com journal homepage: www.elsevier.com/jbmt Journal of Bodywork & Movement Therapies (2011) xx,1e7 + MODEL Please cite this article in press as: Lima, Pedro Olavo de Paula, et al., Reproducibility of the pressure biofeedback unit in measuring transversus abdominis muscle activity in patients with chronic nonspecific low back pain, Journal of Bodywork & Movement Therapies (2011), doi:10.1016/j.jbmt.2011.06.003 1360-8592/$ - see front matter ª 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jbmt.2011.06.003