Natalie Hezel ^1* Theresa Buchner ¹ Clemens Becker ² Jürgen M. Bauer ¹ Lizeth H. Sloot ^3,4 Simon Steib ⁵ Christian Werner ¹

• ¹ Geriatric Centre, Heidelberg University Hospital, Agaplesion Bethanien Hospital Heidelberg, Heidelberg, Germany
• ² Unit of Digital Geriatric Medicine, Heidelberg University Hospital, Heidelberg, Germany
• ³ Institute of Computer Engineering, Faculty of Mathematics and Computer Science, Heidelberg University, Heidelberg, Baden-Württemberg, Germany
• ⁴ Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, England, United Kingdom
• ⁵ Department of Human Movement, Training and Active Aging, Institute of Sports and Sports Science, Heidelberg University, Heidelberg, Germany

Introduction: The ability to respond effectively to external perturbations is crucial for avoiding falls. The Stepping Threshold Test (STT) has been developed to assess this reactive balance, but its ability to discriminate between fallers and non-fallers is still unsubstantiated. This study aimed to evaluate the discriminant validity of the STT in distinguishing fallers and non-fallers and its convergent validity. Methods: Thirty-six older adults (age=80±5 years), with 13 (36%) of them reporting a fall history in the past year, completed the STT on a perturbation treadmill. They received surface perturbations of progressively increasing magnitude while standing. Single- and multiple-step thresholds were assessed using an all-step count evaluation (STT-ACE), and a direction-sensitive evaluation strategy (STT-DSE). Receiver operating characteristics and area under the curves (AUC) were analyzed to evaluate the discriminative accuracy. Convergent validity was explored by13 hypothesized associations with other mobility, psychological, and cognitive assessments. Results: Fallers and non-fallers significantly differed in the STT-DSE (p=0.033), but not in the STT-ACE or other commonly used mobility assessments. Acceptable discriminative accuracy was obtained for the STT-DSE (AUC=0.72), but not for the STT-ACE and other mobility assessments (AUC=0.53-0.68). Twelve (92%) associations were consistent with our hypotheses for the STT-DSE, and ten (77%) for the STT-ACE. Conclusion: Our findings provide preliminary evidence that the STT, when using the STT-DSE, may discriminate between older adult fallers and non-fallers. The STT appears to be a valid tool for assessing reactive balance, with its STT-DSE being recommended due to its better discriminant and convergent validity compared to the STT-ACE.