Objective: The purpose of this study was to compare changes in thickness of the transverse abdominis during performance of the hollowing exercise guided by feedback using ultrasonography images together with verbal guidance and using verbal guidance alone. We also determined the minimal detectable change and agreement between normalized pressures and muscle thickness.

Methods: Twenty participants without lumbar pain performed the hollowing exercises with or without ultrasonography feedback: 7 men and 13 women, mean (SD) age = 25 (5) years, height = 166 (10) cm, body mass = 64 (6) kg, body mass index = 22.2 (5.8) kg/m². The thickness of the transverse abdominis was quantified during the exercise using musculoskeletal ultrasonography. Basal and 3 repetitions guided by an evaluator were performed. Pressure was determined using a lumbar cushion. Data were compared with a mixed-model analysis of variance and Bonferroni post hoc test (P < .05). Minimal detectable changes were identified and Bland-Altman analysis performed considering normalized thickness and pressure.

Results: Ultrasonography feedback resulted in larger thickness changes (P < .05). The lowest minimal detectable changes were achieved using ultrasonography feedback. Nonagreement was found between normalized thickness and pressure.

Conclusion: Contraction of the transverse abdominis is improved using real-time ultrasonography together with verbal feedback. Low changes in muscle contraction estimated by thickness showed nonagreement with a pressure cushion.

Author keywords: Biofeedback, Ultrasonography, Lumbar

Author affiliations: CDlF: Carrera de Kinesiología, Departamento de Ciencias de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; Laboratorio LIBFE, Escuela de Kinesiología. Universidad de los Andes, Santiago, Chile; Centro de Salud Deportivo, Clínica Santa María, Santiago, Chile; RS: Carrera de Kinesiología, Departamento de Ciencias de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; Clínica MEDS, Santiago, Chile; PB, AG, KG, MV, VW, MD: Carrera de Kinesiología, Departamento de Ciencias de la Salud, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; FPC: Laboratory of Neuromechanics, Universidade Federal do Pampa, Campus Uruguaiana, Uruguaiana, Brazil.

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