Early detection of frailty is crucial for older adults’ health, particularly as lower limb muscle strength declines rapidly in the early stages of frailty. The five times sit-to-stand (FTSTS) test is commonly used to evaluate this strength. However, performing the FTSTS test at maximum effort poses risks, requiring assistance to prevent falls and increasing the likelihood of excessive strain on lower limb joints. Therefore, safer, less strenuous methods for assessing muscle strength are needed to minimize these risks. Therefore, to measure lower limb function in a safe environment, it is necessary to implement a version of the FTSTS test that does not require maximum effort speed, allowing the subject to perform at their own pace with minimal physical strain, and to develop a method to automate this measurement. This study proposes a method to assess frailty and fall risk by conducting the FTSTS test with minimal exertion and analyzing acceleration data. A system using a wearable accelerometer with wireless communication capabilities was developed to automatically measure the acceleration during the sit-to-stand movements. The J-CHS (Japanese version of the Cardiovascular Health Study) criteria for frailty diagnosis and the Kihon Checklist for fall risk assessment were conducted, and the results were used as a control for categorizing subjects based on frailty and fall risk. Clinical trials of the FTSTS test were conducted on older adults, and frailty and fall risk were assessed based on the acceleration data obtained to verify the effectiveness of the proposed method.

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