The aim of this master’s thesis was to examine the measurement characteristics of the Flywheel Squat test in older adults. We assessed both the test–retest reliability and validity of the Flywheel Squat test, comparing the results with established functional tests, namely the Timed Up and Go and the Five Times Sit-to-Stand tests, as well as knee extensor and flexor strength measured on an isokinetic device. A total of 30 participants, aged 54 to 81 years (8 men and 22 women), were included in the study. Participants attended three testing sessions: the first two sessions were conducted one week apart, and the third session was performed 10 weeks after the second. During each visit, participants performed four tests in randomized order: Flywheel Squat, knee extension and flexion on an isokinetic device, Timed Up and Go, and Five Times Sit-to-Stand. Randomization was used to minimize the systematic effects of fatigue on test outcomes. The main findings indicate that the Flywheel Squat test in older adults provides reliable results, both in terms of relative reliability, represented by the intraclass correlation coefficient (ICC2.1), and absolute reliability, represented by the coefficient of variation (CV), within the expected limits (ICC2.1 = 0,75–1; CV < 10 %). According to the ICC2.1 criterion, good to excellent reliability (ICC2.1 > 0,75; CV < 10%) was observed for three squat mechanical variables (velocity, force, and power) with velocity being the most and power the least reliable. The highest reliability for velocity was observed at a load of 0,075 kg∙m² (ICC2.1 = 0,89), while the lowest reliability was found for power at a load of 0,025 kg∙m² (ICC2.1 = 0,76). Validity analysis showed that the Flywheel Squat test is a valid assessment in older adults, exhibiting statistically significant correlations with the established functional tests Timed Up and Go and Five Times Sit-to-Stand. The strength of these correlations increased with the number of visits, highlighting the importance of familiarization with the test protocol. The Flywheel Squat test also showed significant correlations with isokinetic strength measurements, with high correlations observed between mechanical variables in the concentric phase of the squat with knee flexor and extensor strength, and moderate to high correlations between mechanical variables in the eccentric phase of the squat with knee flexor and extensor strength, at both 60°/s and 180°/s. In conclusion, the Flywheel Squat is a complex but useful and valid test for assessing lower extremity strength and power in older adults. Initial familiarization and introductory repetitions are necessary to ensure valid and reliable results. Our findings underscore that familiarization with the test protocol is a crucial component of both training and assessment on flywheel devices among the older adults, given the technical demands and accentuated eccentric loading, which may be particularly challenging for this age group.
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