Test–retest reliability, convergent validity, and feasibility of three different five-sit-to-stand tests in women with and without diastasis recti abdominis: a cross-sectional study

Background Objective methods for assessing abdominal muscle function in women with diastasis recti abdominis (DRA) are currently limited. This study aimed to determine the test-retest reliability, convergent validity, and feasibility of a five-sit-to-stand test (5-STS) from three different chair heights in women with and without DRA.Methods Forty age- and body-mass-index-matched women with and without DRA were included in a cross-sectional study with a test-retest design. The performances of three 5-STS tests were assessed in random order, from chair heights of 43 cm, 20 cm, and an individually set height, along with an isometric abdominal muscle strength test for comparison. Relative test-retest reliability was assessed by Intraclass Correlation Coefficients (ICC), absolute reliability using Standard Error-of-Measurement (SEM) and minimal detectable change (MDC). Convergent validity was explored through correlations with key clinical characteristics, including age, inter-recti distance width, body perception, back pain, and quality-of-life. Feasibility measures included completion rates, symptoms, and adverse events.Results All 5-STS tests were feasible, with moderate to excellent relative reliability (ICC = 0.681–0.949) and comparable absolute reliability (SEM = 0.70–0.86 s, MDC = 1.95–2.39 s). Among the women with DRA, convergent validity measurements revealed significant moderate to very large correlations between the 5-STS test results, specifically the 5-STS 43 cm chair height test, and inter-recti distance width, abdominal circumference, body perception, and back paine (rho −0.549 to 0.735).Conclusion The 5-STS test performed from a standard 43 cm chair height emerged as the most promising due to feasibility, moderate to excellent test-retest relative reliability, good absolute reliability, and convergent validity.