Measurement reliability and cooperative movement of the pelvic floor and transverse abdominal muscles

[Purpose] This study examined the measurement reliability and cooperative movement of the pelvic floor and transverse abdominal muscles. [Participants and Methods] The participants were seven healthy adult females. Transverse abdominal muscle thickness and bladder floor elevation were measured under the following conditions during active exercise and during resistance exercise: the resting state, maximum contraction of the transverse abdominal muscle, maximum contraction of the pelvic floor muscle, and maximum co-contraction of the transverse abdominal and pelvic floor muscles. Measurements were taken at rest and under each exercise condition. [Results] The intraclass correlation coefficients of transverse abdominal muscle thickness and bladder floor elevation showed high reproducibility under all conditions. The maximum contraction of the pelvic floor muscle showed a high correlation with the maximum co-contraction of the transverse abdominal muscle and pelvic floor muscle during resistance exercise. A significant regression line was found between transverse abdominal muscle thickness and bladder floor elevation under all conditions. The regression equation was as follows: transverse abdominal muscle thickness=0.113 bladder floor elevation+0.377 (r2=0.21). [Conclusion] This study demonstrated that the measurement reliability of the transverse abdominal and pelvic floor muscles is high, and that both muscles exhibit cooperative movement.