State-of-the-Art: Falls are the consequence of gait and balance disturbances of older adults and frail older patients, and may lead to fractures, with hip fractures among the most regularly occurring and having the worst consequences. Loss of muscle mass, power and function, i.e. sarcopenia, is a main cause of falls. The interplay between sarcopenia, gait and balance deficits, and falls is however not well understood. It is in particular unclear whether different causes of sarcopenia (e.g. due to muscle, neuromuscular junction (NMJ)  or motor neuron pathology) differently affect gait and balance.

Approach: The overall aim is to define different causes of sarcopenia, and to test their respective contribution to gait and balance deficits in a cohort of sarcopenic patients with an acute hip fracture, by investigating muscles on a functional, biochemical and histological level, and to compare these results with ICF-relevant baseline parameters, rehabilitation outcome and gait and balance parameters after recovery. We will recruit patients from orthopedic and traumatological wards, planned for surgery, and will assess defined sarcopenia-associated muscle mass and function parameters. Moreover, electromyographical measurements  will be performed, and –during surgery– a muscle biopsy of the vastus lateralis muscle will be taken for histological, biochemical and immunohistochemical analyses. Patients will then be followed during the rehabilitation process until full recovery / steady state condition, with regular assessment of gait and balance parameters. These assessments will allow, to our knowledge for the first time, a direct comparison of sarcopenia, falls and gait and balance deficits by combining high quality histological, biochemical and immunohistochemical data with functional and ecologically relevant data.