Researcher(s)
- Meghna Raj Annasagaram, Biomedical Engineering, University of Delaware
Faculty Mentor(s)
- Stephanie Cone, Biomedical Engineering, University of Delaware
Abstract
The Achilles tendon transmits and stores energy for plantarflexion movements, including gait. It is made up of three subtendons that insert at the medial gastrocnemius, lateral gastrocnemius, and soleus, collectively known as the triceps surae. Two common Achilles tendon injuries are Achilles tendinopathy, which is characterized by tendon overuse leading to inflammation, and Achilles tendon rupture, which involves a complete or partial tear and is associated with rapid trauma.
Our previous research and literature have identified ultrasound and MRI differences between these two Achilles tendon injuries [1]. However, to determine whether increased cross-sectional area or volume signifies a positive or negative rehabilitation outcome, morphological data must be coupled with electromyography (EMG) data, which depicts the timing and amplitude of neuromuscular force activation. This study elucidates the MRI and EMG differences between Achilles tendinopathy and Achilles tendon rupture.
Three groups were studied: healthy controls, Achilles tendinopathy, and Achilles tendon rupture (n=15). Subjects underwent MRI and performed plantarflexion and heel raises with EMG. MATLAB code processed EMG signals, comparing maximum amplitude and integral EMG for each muscle per side. Intramuscular fat distribution was calculated for proximal, middle, and distal muscle regions from the MRIs.
We expect atypical EMG patterns in the soleus on the ruptured side compared to the intact side due to previously found differences in cross-sectional area (CSA). Activation amplitude should correspond to CSA, with soleus having the highest amplitude, followed by medial and lateral gastrocnemius. Healthy subjects should show a fat fraction less than 10% and uniform fat fraction distributions [2], while injury groups may show atypical fat fraction values.
These findings will inform rehabilitation and surgical strategies for Achilles tendon injuries. Future work will involve larger samples to address sex differences [3] and consider differences between bilateral vs unilateral injury presentations.
[1] H. P. Smitheman et al., “Measurement of Healthy and Injured Triceps Surae Morphology,” Journal of Visualized Experiments (JoVE), no. 200, p. e65798, Oct. 2023, doi: 10.3791/65798.
[2] S. Pinel, N. Y. Kelp, J. M. Bugeja, B. Bolsterlee, F. Hug, and T. J. M. Dick, “Quantity versus quality: Age-related differences in muscle volume, intramuscular fat, and mechanical properties in the triceps surae,” Experimental Gerontology, vol. 156, p. 111594, Dec. 2021, doi: 10.1016/j.exger.2021.111594.
[3] W. H. Elsayed, “Differences in triceps surae muscle dynamometry and electromyography between adult males and females,” Medicine (Baltimore), vol. 104, no. 36, p. e44349, Sep. 2025, doi: 10.1097/MD.0000000000044349.