Thesis
Impact of forefoot biasing footwear and modeling approaches on Achilles tendon loading estimates during dynamic movements
University of Iowa
Master of Science (MS), University of Iowa
Spring 2025
DOI: 10.25820/etd.007930
Abstract
The Achilles tendon is an important link between the triceps surae plantarflexors and the calcaneus, transmitting force developed by the muscles into movement of the ankle joint. The Achilles tendon is subjected to repetitive loading from everyday activities, like walking. Despite being the strongest tendon in the body,3 acute increases in loading placed on the tendon can cause degeneration of its structural components, ultimately resulting in the development of Achilles Tendinopathy (AT).4
While exercise-based rehabilitation is considered the gold standard for treating AT,5, 6 pain and functional deficits persist in many individuals for years after treatment.7-9 It is unknown why conservative management of AT does not result in greater functional outcomes and why reinjury rates are high,10 suggesting the need for more effective loading strategies. Footwear has been shown to influence tendon loading11-13 and may serve as a valuable tool for progressing tendon loading during rehabilitation for AT.
Most research quantifying tendon loading during AT rehabilitation exercises have studied able-bodied participants.14-16 However, because of the presence of pain and the fact that degenerative changes in the tendon can impact its mechanical and force-transmitting properties,4, 6, 9 there may be differences in how activities are performed and the tendon is loaded in individuals with AT compared to controls. The potential differences could influence the selection of activities during treatment and, ultimately, the effectiveness of the intervention.
Furthermore, directly measuring Achilles tendon loading in vivo is highly invasive.15, 17, 18 Researchers commonly use two different methodologies to estimate tendon loading, but it is unknown if the two approaches produce comparable results for loading during rehabilitation exercises. The potential differences between these methodologies make it difficult to compare loading estimates across studies19 and may affect clinical recommendations.
This work explored how footwear that biases foot loading toward the forefoot20, 21 affects ankle kinematics, ankle kinetics, and Achilles tendon loading during exercises used for AT treatment in a control group and a group of individuals with symptomatic midportion AT. Forefoot biasing footwear was found to influence ankle kinematics and the cumulative loading on the tendon across activities, but its influence on peak tendon load and loading rate varied. These findings were similar for both participant groups.
Estimates of tendon loading obtained using a simplified fixed moment arm approach based on the ankle moment were compared to estimates obtained using musculoskeletal modeling. Tendon loading estimates from musculoskeletal modeling were consistently greater and more variable than the simplified approach related to the ankle moment. Values obtained using the simplified approach were more closely aligned with in vivo studies and can be easily implemented.
Details
- Title: Subtitle
- Impact of forefoot biasing footwear and modeling approaches on Achilles tendon loading estimates during dynamic movements
- Creators
- Sara M. Magdziarz
- Contributors
- Jason Wilken (Advisor)Donald Anderson (Advisor)Colleen Bringman (Committee Member)Ruth Chimenti (Committee Member)Jessica Goetz (Committee Member)Nicole Kallemeyn (Committee Member)David Williams (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Biomedical Engineering
- Date degree season
- Spring 2025
- DOI
- 10.25820/etd.007930
- Publisher
- University of Iowa
- Number of pages
- xii, 65 pages
- Copyright
- Copyright 2025 Sara M. Magdziarz
- Language
- English
- Date submitted
- 04/17/2025
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 54-61).
- Public Abstract (ETD)
The Achilles tendon connects the calf muscles to the heel, playing an important role in movements like walking. Sudden increases in tendon loading can lead to Achilles Tendinopathy (AT), a condition characterized by pain and tendon degeneration.4 Although exercise-based rehabilitation is standard for conservative AT treatment,5, 6 many individuals continue to experience pain and reduced function after rehabilitation.7-9 The reasons for these ongoing deficits remain unclear, suggesting the need for improved loading strategies. Footwear modifications, which can influence tendon loading,11-13 may be valuable for progressing exercise intensity during AT rehabilitation.
Most research estimating tendon loading during rehabilitation exercises has studied able-bodied individuals.14-16 However, pain accompanied by degenerative tendon changes with AT may alter activity performance and loading, potentially affecting long-term outcomes.4, 6, 9 Furthermore, direct measurements of Achilles tendon loading are invasive,15, 18, 22 and differences in estimation methods remain unclear, making it difficult to compare findings across studies.19
This work explored how footwear biasing foot loading toward the forefoot20 could influence ankle positioning and tendon loading in both able-bodied individuals and those with AT. Results showed that forefoot biasing footwear could influence ankle positioning and total tendon load across activities, but its impact on peak load and loading rate varied.
Additionally, tendon loading estimates were compared between a simplified approach based on the ankle moment and a musculoskeletal modeling approach. Tendon loading estimates with modeling were highly variable compared to the simplified approach, which more closely aligned with in vivo studies and is easily implemented.
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering
- Record Identifier
- 9984830728402771
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