Biomechanics research is at a crucial stage where researchers are seeking to translate results in the lab into results in the real world. However, most technologies that have been foundational to biomechanics research, such as optical motion capture systems, force plates, instrumented treadmills, and robotic exoskeletons, are restricted to use in the lab. In order to address this problem, biomechanists have sought to implement other approaches, one of the foremost being wearable technologies. The purpose of this dissertation was to develop wearable technology for measuring and assisting human motion outside of the lab.

In Aim 1, we validated a novel insole pressure sensor for quantifying ground reaction force (GRF) during walking. We collected data from 7 participants walking on an instrumented treadmill while wearing the insole pressure sensor. This sensor was validated by quantifying agreement with gold-standard force plate measurements of peak GRF during walking at three different speeds. We found that this sensor could achieve moderate agreement with the force plate with a basic calibration procedure and a low-cost data acquisition system, which suggests potential to overcome the economic barrier to more widespread adoption of this technology.

In Aim 2, we optimized cable-driven exosuit properties using musculoskeletal modeling and simulation. We recruited 5 healthy adult subjects to perform reaching, drinking, and hair-brushing motions, and used kinematics of these motions as inputs into a musculoskeletal model. We ran computed muscle control (CMC) simulations to first estimate unassisted muscle activity for these tasks, and then ran an optimization algorithm involving successive CMC simulations with different cable actuator properties. We used this optimization algorithm to identify optimal cable actuator attachment points and forces to minimize the combined activity of the middle and anterior deltoids. This method successfully identified optimal actuator properties that substantially reduced activity of the target muscles for all three motions.

In Aim 3, we developed and tested a physical prototype of a shoulder exosuit for reaching and drinking assistance. In this study, we collected kinematic, EMG, and exosuit force data to evaluate how individuals altered motion in response to exosuit assistance. Subjects performed a series of reaches while not wearing the exosuit, while wearing the exosuit without assistance, and wearing the exosuit with assistance. In total, 200 reaches were performed with 120 reaches assisted by the exosuit to allow subjects to learn how to use the device. Subjects also performed drinking motions with and without powered assistance from the exosuit. We found that the exosuit successfully reduced muscle activity of the middle and posterior deltoids during reaching and drinking. Furthermore, we found that individuals altered kinematics in response to the exosuit by allowing their arms to follow exosuit assistance. Finally, we found that subjects exhibited trial-to-trial changes in movement duration and in the timing at which they used a switch to activate the exosuit. Future work should seek to evaluate the learning mechanisms behind changes in muscle activity and movement duration when using an exosuit and to integrate experimental results with musculoskeletal modeling and simulation to improve exosuit design.