Wearable Sensing of Achilles Tendon Loading during Functional Movements

• Melanie Napierala, Biomedical Engineering, Fairfield University
• Jack Felipe, Biomedical Engineering, University of Delaware

• John Drazan, Biomedical Engineering, Fairfield University
• Stephanie Cone, Biomedical Engineering, University of Delaware

Traditionally, motion capture and force plates are used to measure tendon loading. Shear wave tensiometry uses a mechanical tapper to induce a shear wave and two accelerometers of a known distance apart to measure shear wave speed, offering a non-invasive and wearable approach to measure tendon load. Currently, there is limited published data using shear wave tensiometry to study tendon loading during sport-specific functional movements, as most prior research focused on walking and running. Therefore, the purpose of this study was to implement a shear wave tensiometer to measure differences in Achilles tendon loading across a battery of functional movements. In this study, 19 healthy participants performed 9 tasks (double legged heel raises, single legged heel raises, squats, walking, countermovement jumps, double legged forward-backward hops, single legged forward backward hops, double legged side-to-side hops, and single legged side-to-side hops) with a shear wave tensiometer on their left Achilles tendon. For each movement, participants completed 5 repetitions; during walking trials, participants took an average of 3 strides. The wave speed data was processed using custom MATLAB code which normalized all movements to the participants’ double heel raise. Mean cycle data was plotted in MATLAB and raw and normal peaks were collected, averaged across all participants, and compared. Similar to studies that have used inverse dynamics to estimate tendon loading, we observed that stationary tasks such as squats produced lower tendon loading compared to high impact movements such as jumping. As a part of an ongoing study, ultrasound images of the participants’ left Achilles tendons were collected, and commercial force sensing insoles (loadsol, novel) were used in the data collection. Future work will include comparing the metrics collected from the shear wave tensiometer and loadsol sensors to validate use of instrumented insoles for approximating Achilles tendon loading.