Considerations on the human Achilles tendon moment arm for in vivo triceps surae muscle–tendon unit force estimates

Holzer, Denis; Paternoster, Florian Kurt; Hahn, Daniel; Siebert, Tobias; Seiberl, Wolfgang

doi:10.1038/s41598-020-76625-x

“…The study was conducted according to the declaration of Helsinki. The study was a side‐project of a long‐term research project which has Ethics approval, sharing the same methods (Holzer et al, 2020). Therefore, no separate approval was obtained.…”

Section: Methodsmentioning

confidence: 99%

“…The reference electrode was placed on the lateral malleolus of the contralateral foot. Skin preparation and electrode placement were performed according to the SENIAM guidelines (Hermens et al, 1999).…”

Section: Methodsmentioning

confidence: 99%

Residual force enhancement in humans: Is there a true non‐responder?

Paternoster

¹

,

Holzer

²

,

Arlt

³

et al. 2021

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When an active muscle is stretched and kept isometrically active, the resulting force is enhanced compared to a purely isometric reference contraction at the same muscle length and activity; a generally accepted muscle property called residual force enhancement (rFE). Interestingly, studies on voluntary muscle action regularly identify a significant number of participants not showing rFE. Therefore, the aim was to unmask possible confounders for this non‐responsive behavior. Ten participants performed maximum voluntary isometric plantarflexion contractions with and without preceding stretch. Contractions were accompanied by the assessment of voluntary activation using the twitch‐interpolation technique. The same test protocol was repeated four additional times with a least on day rest in‐between. Additionally, at the first and fifth sessions, a submaximal tetanic muscle‐stimulation condition was added. At both muscle‐stimulation sessions mean rFE higher 10% (p < 0.028) was found. In contrast, during voluntary muscle action, individual participants showed inconsistent rFE across sessions and only one session (#3) had significant rFE (5%; p = 0.023) in group means. As all participants clearly had rFE in electrical stimulation conditions, structural deficits cannot explain the missing rFE in voluntary muscle action. However, we also did not find variability in voluntary activation levels or muscle activity as the confounding characteristics of “non‐responders.”

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“…In that study, we found that when imposing joint kinematics and kinetics, the simulated change in gastrocnemius fiber length in terminal stance exceeded the measured change. In addition, previous studies have reported a wide range of Achilles tendon moment arms, and moment arms determine how muscle-tendon lengths change with joint angles [39][40][41]. We therefore believe that more accurately modeling plantarflexor geometry might improve simulated ankle angles.…”

Section: Discussionmentioning

confidence: 91%

“…CC-BY 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is The copyright holder for this preprint this version posted August 13, 2021. ; https://doi.org/10.1101/2021.08.13.456292 doi: bioRxiv preprint angles [39][40][41]. We therefore believe that more accurately modeling plantarflexor geometry might improve simulated ankle angles.…”

Section: Discussionmentioning

confidence: 99%

Modeling toes contributes to realistic stance knee mechanics in three-dimensional predictive simulations of walking

Falisse

¹

,

Afschrift

²

,

Groote

³

2021

Preprint

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Physics-based predictive simulations have been shown to capture many salient features of human walking. Yet they often fail to produce realistic stance knee mechanics and terminal stance ankle plantarflexion. While the influence of the performance criterion on the predicted walking pattern has been previously studied, the influence of the mechanics has been less explored. Here, we investigated the influence of two mechanical assumptions on the predicted walking pattern: the complexity of the foot segment and the stiffness of the Achilles tendon. We found, through three-dimensional muscle-driven predictive simulations of walking, that modeling the toes and metatarsophalangeal joints, and thus using two-segment instead of single-segment foot models, contributed to robustly eliciting physiological stance knee flexion angles, knee extension torques, and knee extensor activity. Yet modeling toe joints did not improve ankle kinematics, nor did decreasing the Achilles tendon stiffness. The lack of predicted terminal stance ankle plantarflexion thereby remains an open question. Overall, this simulation study shows that not only the performance criterion but also mechanical assumptions affect predictive simulations of walking. Improving the realism of predictive simulations is required for their application in clinical contexts. Here, we suggest that using complex models is needed to yield such realism.

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“…The tendon excursion (TE) method was used to estimate the moment arm, which has been well-detailed documented in literature [ 17 , 20 ]. The TE method is based on the principle of virtual work, which computes the moment arm as the first derivative of the ratio of the change in muscle-tendon length to the changes in the angle of the corresponding joint [ 17 , 21 ].…”

Section: Determination Of Passive Mechanical Properties Of Tendon mentioning

confidence: 99%

Passive Mechanical Properties of Human Medial Gastrocnemius and Soleus Musculotendinous Unit

Wang

¹

,

Yan

²

,

Schlippe

³

et al. 2021

BioMed Research International

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The in vivo characterization of the passive mechanical properties of the human triceps surae musculotendinous unit is important for gaining a deeper understanding of the interactive responses of the tendon and muscle tissues to loading during passive stretching. This study sought to quantify a comprehensive set of passive muscle-tendon properties such as slack length, stiffness, and the stress-strain relationship using a combination of ultrasound imaging and a three-dimensional motion capture system in healthy adults. By measuring tendon length, the cross-section areas of the Achilles tendon subcompartments (i.e., medial gastrocnemius and soleus aspects), and the ankle torque simultaneously, the mechanical properties of each individual compartment can be specifically identified. We found that the medial gastrocnemius (GM) and soleus (SOL) aspects of the Achilles tendon have similar mechanical properties in terms of slack angle (GM: − 10.96 ° ± 3.48 ° ; SOL: − 8.50 ° ± 4.03 ° ), moment arm at 0° of ankle angle (GM: 30.35 ± 6.42 mm; SOL: 31.39 ± 6.42 mm), and stiffness (GM: 23.18 ± 13.46 Nmm-1; SOL: 31.57 ± 13.26 Nmm-1). However, maximal tendon stress in the GM was significantly less than that in SOL (GM: 2.96 ± 1.50 MPa; SOL: 4.90 ± 1.88 MPa, p = 0.024 ), largely due to the higher passive force observed in the soleus compartment (GM: 99.89 ± 39.50 N; SOL: 174.59 ± 79.54 N, p = 0.020 ). Moreover, the tendon contributed to more than half of the total muscle-tendon unit lengthening during the passive stretch. This unequal passive stress between the medial gastrocnemius and the soleus tendon might contribute to the asymmetrical loading and deformation of the Achilles tendon during motion reported in the literature. Such information is relevant to understanding the Achilles tendon function and loading profile in pathological populations in the future.

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Considerations on the human Achilles tendon moment arm for in vivo triceps surae muscle–tendon unit force estimates

Cited by 18 publications

References 66 publications

Residual force enhancement in humans: Is there a true non‐responder?

Residual force enhancement in humans: Is there a true non‐responder?

Modeling toes contributes to realistic stance knee mechanics in three-dimensional predictive simulations of walking

Passive Mechanical Properties of Human Medial Gastrocnemius and Soleus Musculotendinous Unit

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