Background: Many older adults with physical limitations living in residential care apartments are unable to exercise in a standing position and are at risk for declining in muscle function leading to falls and injury. Novel approaches to achieve exercise benefts are needed. The purpose of this study was to test the efect of semi-recumbent vibration exercise on muscle outcomes in older adults living in residential care apartment complexes (RCACs). Methods: A randomized, crossover design was used to examine the efect of semi-recumbent vibration exercise on muscle function and mass among 32 RCAC residents (mean age 87.5 years) with physical limitations. Participants received a randomized sequence of two study conditions: sham or vibration for 8 weeks each separated by a 4-week washout. Before and after the 8 weeks of vibration treatment and sham treatment, muscle mechanography was used to assess muscle function including jump power, weight-corrected jump power, and jump height. Short physical performance battery (SPPB) and handgrip strength were also used to measure muscle function. Bioelectrical impedance spectroscopy was used to estimate skeletal muscle mass. The efect of the vibration treatment on muscle outcomes was analyzed through mixed efects linear regression models. Results: Vibration exercise leads to better jump height (p<.05) compared to sham exercise but also poorer chair rise performance (p=0.012). Other muscle functions tests and muscle mass parameters showed non-signifcant changes. Conclusion: This small pilot study showed no conclusive results on the efect of semi-recumbent vibration exercise on muscle function and mass in older adults living in RCAC. However, the promising signals of improved jump performance could be used to power larger studies of longer duration with various vibration doses to determine the beneft of vibration exercise in this physically impaired, high-risk population with few exercise capabilities.