Triceps surae muscle forces during dynamic exercises in patients with Achilles tendinopathy: A cross‐sectional study

Abstract

PurposeThe aim of this study was to investigate the individual triceps surae muscle forces during the execution of six different functional movements and rehabilitation exercises in patients with Achilles tendinopathy compared to a control group.MethodsTriceps surae muscle forces of 15 participants with Achilles tendinopathy (AT) and 15 healthy controls were estimated through a combination of experimental data and musculo‐skeletal modeling. Three‐dimensional motion capture and force plates were used to collect the ankle and knee joint angles and moments during three functional movements (walking, heel walking, and toe walking) and three rehabilitation exercises (bilateral heel drop, unilateral heel drop with extended knee and with flexed knee). A dynamic optimization method was used to obtain the modeled triceps surae muscle forces. Force‐sharing strategies were calculated at the peak triceps surae muscle force and compared between groups.ResultsLower peak triceps surae forces were obtained for the AT group during dynamic exercises. Across all exercises, the average contribution of the soleus (SOL) to the total triceps surae muscle force was the largest (60.83 ± 13.89% [AT] > 56.90 ± 16.18% [healthy]), followed by the gastrocnemius medialis (29.87 ± 10.67% [AT] < 32.19 ± 12.90% [healthy]) and the gastrocnemius lateralis (9.30 ± 4.31% [AT] < 10.91 ± 4.66% [healthy]). The triceps surae force‐sharing strategy was different for the toe walking, heel walking, and the bilateral and unilateral heel drop with extended knee.ConclusionThis study provides evidence for altered triceps surae muscle force‐sharing strategies during dynamic tasks in patients with AT. The influence of altered muscle force‐sharing on the subtendon nonuniformity and/or the tendon loading should be explored in future work.

Patients with Achilles Tendinopathy use compensation strategies to reduce tendon load during rehabilitation exercises

“…Moreover, our results highlight the importance of physiotherapists providing clear instructions and feedback about the performed exercises as small differences in knee and ankle angles can result in altered loading of the Achilles tendon. Additionally, our results and previous research (43) suggested that during daily activities such as walking, the Achilles tendon already undergoes a considerable amount of peak loading, yet with a lower loading rate. Therefore, it seems important to better account for this daily cumulative load during the rehabilitation.…”

“…Additionally, our results and previous research (43) suggested that during daily activities such as walking, the Achilles tendon already undergoes a considerable amount of peak loading, yet with a lower loading rate. Therefore, it seems important to better account for this daily cumulative load during the rehabilitation.…”

“…Alteration in force distribution may indicate a different loading pattern in the Achilles tendon of patients with AT compared to healthy individuals. Indeed, Mylle et al (43) observed an altered load distribution in patients with AT during rehabilitation and walking exercises, which may potentially impact the sliding between the subtendons (44, 45). This observation suggests that the load distribution within the Achilles tendon could be an important factor in the development and progression of AT.…”

How subject-specific biomechanics influences tendon strains in Achilles tendinopathy patients: A finite element study

“…In line with previous results (Hansen et al, 2017; Shim et al, 2019), it becomes evident that when creating subject-specific models, prioritizing not only subject-specific geometry but also subject-specific muscle forces over material properties, is crucial for a more accurate representation of the AT strains, especially when considering Achilles tendinopathy patients. Mylle et al . (2023) demonstrated a different force distribution strategy between Achilles tendinopathy patients and healthy controls.…”

“…Moreover, the differential force exerted by the triceps surae muscles plays a crucial role in the elongations of the sub-tendons, subsequently the strains in the AT. In individuals with Achilles tendinopathy, there is a noticeable change in the force distribution strategies employed by the triceps surae muscles during dynamic tasks (Mylle et al, 2023). Consequently, it becomes pivotal to consider the impact of triceps surae muscle forces on AT when examining the factors contributing to strain development in patients with Achilles tendinopathy.…”