Project Summary The goal of this project is to commercialize a wireless, wearable system to estimate the tension in superficial tendons throughout the limbs during dynamic movements. Tendon tension provides an estimate of muscle force, which is important information for understanding biomechanical behavior in all types of movement. Understanding muscle-tendon function inside the body is especially important for rehabilitation from musculoskeletal injuries: this information can elucidate the effectiveness of therapy, provide biofeedback to improve this effectiveness, and evaluate the level of impairment and recovery as a person progresses through recovery. Yet, muscle-tendon function has previously been difficult to measure. Tendon tensiometry uses skin- mounted accelerometers to track the propagation of shear waves along a tendon, after the waves are induced by a light mechanical tap on the tendon. The speed of wave propagation depends on the tension in the tendon, so measuring wave speed provides a measurement of tendon tension. The proposed project will build and test a wearable system to make these tendon tension measurements during free movement. These measurements promise to enable new methods of injury assessment, rehabilitation, and treatment of musculoskeletal disorders. This will refine current prototype tensiometry technology into a commercial product to allow convenient outdoor wearable data collections of muscle-tendon mechanics. It will refine the skin-mounted sensor and mounting sleeves for different joints and tendons. It will integrate drive and data logging electronics into a convenient, wearable multi-channel controller. It will create efficient programs to process the signals for real-time data streaming, and user interfaces for clinical monitoring of tendon tensiometry in common movements. The project will also develop means of convenient subject-specific calibration. Human subjects testing will be performed to establish a database of tendon loading profiles in healthy young and older adults. Finally, the research will develop methods to fuse tendon tension data with wearable movement sensor data to improve the quality of biomechanical insight available from real- world testing. The Specific Aims of this project are: 1. Establish a wearable shear wave tensiometer that is usable on multiple tendons by non-experts. 2. Build a software system for real-time wireless transmission and display of tensiometer metrics. 3. Integrate wearable tensiometers and inertial sensors to enable motion analysis in the real world.