Reliability, accuracy, and responsiveness of the five-repetition sit-to-stand estimated power for detecting menopausal status and monitoring intervention effects in women

This study aimed to determine whether menopausal status (MS) is associated with output power in the five-repetition sit-to-stand test and to assess the reliability, accuracy, and sensitivity of an equation-based power estimate in postmenopausal women (PMW). A total of 122 women (100 PMW) performed the five-repetition sit-to-stand (5STS) test on a force platform. Power was analyzed for reliability, accuracy, and responsiveness using baseline, test-retest, and training data. MS significantly influenced power (p < 0.01), with an interaction between age and MS (p = 0.038). Estimated power showed excellent test-retest reliability (intra-class correlation coefficient (ICC) = 0.90) and agreement (ICC = 0.87), increasing 7.6% on retest, although prediction error exceeded 45 watts. Compared to platform values, estimated power had good consistency (ICC ≥ 0.88) but moderate agreement (ICC ≤ 0.78), affected by transition time (p < 0.001). After 3 months of resistance training, 75 women showed power gains with both methods (p < 0.05): 7.7% with the equation and 4.3% with the platform (difference of 6.2 watts, p = 0.146). Method agreement in detecting changes was 84%, with similar outcomes in PMW. These findings suggest menopause is linked to lower 5STS power and that the estimation equation offers a reliable, accessible alternative for assessing power in PMW.