Test-retest Reliability Of A Novel Protocol To Evaluate Muscle-tendon Function In Pre- And Post-menopausal Women

Menopause is associated with declines in serum estrogen, which has been shown to alter muscle and tendon properties. Changes in muscle-tendon properties may also have a meaningful impact on muscle, tendon and whole-body function. However, before considering significant and meaningful changes in these variables, quantifying the test-retest reliability of any muscle-tendon function test is required in this active population. PURPOSE: To assess the test re-test reliability of a novel muscle-tendon function protocol in active pre- and post-menopausal women. METHODS: We measured muscle strength and Achilles tendon (AT) stiffness, cross-sectional area (CSA) in six active pre- (n = 3) and post- (n = 3) menopausal women using ultrasonography and dynamometry on two consecutive days. In addition, typically derived metrics of CMJ performance were calculated for this sample population. Test-retest reliability was assessed using interclass-correlation coefficients (ICC). Mean differences (Day1-Day2) and limits-of-agreement (LOA) were calculated from Bland-Altman plots to assess agreement between days. RESULTS: Average maximal muscle force was 2912 ± 769 N and test-retest reliability was moderate (ICC = 0.68). Mean AT stiffness was 195 ± 108 N·mm-1 on Day 1 with good test-retest reliability (ICC = 0.75) on Day 2. AT CSA varied significantly (p < 0.001, η2 = 0.86) across its length, from 58.5 ± 10.8 mm2 at 50% of the AT length to 105.4 ± 17.3 mm2 at the most distal region. Test-retest reliability for AT CSA was good to excellent with the lowest ICC being at 75% of AT length (ICC = 0.74). The largest absolute difference in AT CSA between days was at the most distal region (mean difference 6.4 ± 3.0 mm2, p = 0.086). All other AT regions showed mean differences between days of <2.3 ± 3.1 mm2 (p > 0.49). The test-retest reliability was moderate to excellent for all CMJ metrics (ICC > 0.88), aside from CMJ height (ICC = 0.52). CONCLUSIONS: We have quantified the test-retest reliability of muscle and tendon characteristics using dynamometry and ultrasonography, and during a maximal CMJ to confidently evaluate changes in muscle-tendon function in active pre- and post-menopausal women across future longitudinal studies. Regional differences in AT CSA may have implications for tendon, adaptation and injury prevention. Supported by the Natural Sciences and Engineering Research Council of Canada