Mechanical Coupling Between Muscle-Tendon Units Reduces Peak Stresses

Maas, Huub; Finni, Taija

doi:10.1249/jes.0000000000000132

Cited by 29 publications

(25 citation statements)

References 35 publications

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“…For example, a direct relationship between individual muscle contributions and force distribution across the Achilles tendon has been demonstrated on cadaver preparations (Arndt et al, 1999). Despite it being tempting to conclude that the large individual differences in force-sharing strategies that we report directly translate to individual differences in Achilles subtendon loading, intermuscular force transmission between the heads of the triceps surae may result in a redistribution of force between the Achilles subtendons, as recently suggested (Maas and Finni, 2018). It is also possible that every subtendon exhibits different mechanical properties (related to their elastic modulus, cross-sectional area, length) and that these properties vary between individuals.…”

Section: Coupling Between Muscle Activation and Pcsasupporting

confidence: 66%

Neuromechanical coupling within the human triceps surae and its consequence on individual force sharing strategies

Crouzier

Lacourpaille

Nordez

et al. 2018

Journal of Experimental Biology

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Little is known about the factors that influence the coordination of synergist muscles that act across the same joint, even during single-joint isometric tasks. The overall aim of this study was to determine the nature of the relationship between the distribution of activation and the distribution of force-generating capacity among the three heads of the triceps surae [soleus (SOL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL)]. Twenty volunteers performed isometric plantarflexions, during which the activation of GM, GL and SOL was estimated using electromyography (EMG). Functional muscle physiological cross-sectional area (PCSA) was estimated using imaging techniques and was considered as an index of muscle force-generating capacity. The distribution of activation and PCSA among the three muscles varied greatly between participants. A significant positive correlation between the distribution of activation and the distribution of PCSA was observed when considering the two bi-articular muscles at intensities ≤50% of the maximal contraction (0.51<<0.62). Specifically, the greater the PCSA of GM compared with GL, the stronger bias of activation to the GM. There was no significant correlation between monoarticular and biarticular muscles. A higher contribution of GM activation compared with GL activation was associated with lower triceps surae activation (-0.66<<-0.42) and metabolic cost (-0.74<<-0.52) for intensities ≥30% of the maximal contraction. Considered together, an imbalance of force between the three heads was observed, the magnitude of which varied greatly between participants. The origin and consequences of these individual force-sharing strategies remain to be determined.

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Section: Coupling Between Muscle Activation and Pcsasupporting

confidence: 66%

Neuromechanical coupling within the human triceps surae and its consequence on individual force sharing strategies

Crouzier

Lacourpaille

Nordez

et al. 2018

Journal of Experimental Biology

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“…First, altering relative muscle force contributions from different heads of triceps surae may not appreciably affect relative displacements of different tissue regions. This could be explained by lateral force transmission within the Achilles tendon or via intermuscular myofascial structures that would serve to limit non‐uniform distribution of forces within the Achilles tendon and differential displacements of the tissue regions—a hypothesis recently presented by Maas & Finni . The hypothesis that alterations in triceps surae muscle forces induce only limited changes in Achilles tendon non‐uniform motion due to lateral force transmission is supported by a recent experiment in rat in which isolated contractions of different triceps surae muscles via electrical stimulations resulted in only small variations in displacements of the subtendons .…”

Section: Discussionmentioning

confidence: 85%

Biplanar ultrasound investigation of in vivo Achilles tendon displacement non-uniformity

2018

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The Achilles tendon is a common tendon for the medial and lateral gastrocnemius and soleus muscles. Non‐uniform Achilles tendon regional displacements have been observed in vivo which may result from non‐uniform muscle loading and intratendinous shearing. However, prior observations are limited to the sagittal plane. This study investigated Achilles tendon tissue displacement patterns during isometric plantarflexor contractions in the coronal and sagittal planes. Fourteen subjects (5 female, 9 male, 26 ± 3 year) performed maximal isometric plantarflexor contractions with the knee in full extension and flexed to 110°. An ultrasound transducer positioned over the free Achilles tendon collected beam formed radio frequency (RF) data at 70 frames/s. Localized tissue displacements were analyzed using a speckle tracking algorithm. We observed non‐uniform Achilles tendon tissue displacements in both imaging planes. Knee joint posture had no significant effect on tissue displacement patterns in either imaging plane. The non‐uniform Achilles tendon tissue displacements during loading may arise from the anatomical organization of the sub‐tendons associated with the three heads of the triceps surae. The biplanar investigation suggests that greatest displacements are localized to tissue likely to belong to soleus subtendon. This study adds novel information with possible implications for muscle coordination, function, and muscle‐tendon injury mechanisms.

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“…The results, however, differ between studies, with decrease, increase, and no changes in SO fascicle length reported (reviewed in Ref. 46). In one study, the magnitude of epimuscular forces was estimated to be maximally Ϸ12% of that of passive gastrocnemius (74).…”

Section: Muscle Strains As a Measure Of Epimuscular Myofascial Loads mentioning

confidence: 96%

“…The strain and stress of these linkages are dependent on the relative position of the muscle bellies (44). Despite the fact that the presence of this additional pathway has been reported for several different muscle groups throughout the body (24) and in several animal species [i.e., mouse (33), rat (43), Xenopus laevis (31), locust (56), chicken (5), cat (51), and human (69)], the physiological significance of epimuscular pathways is still subject to debate (20,46,81). Whether these pathways can be considered significant will depend on the relative magnitude of epimuscular forces during in vivo muscle conditions (see below).…”

Section: Introductionmentioning

confidence: 99%

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Significance of epimuscular myofascial force transmission under passive muscle conditions

Maas

2019

Journal of Applied Physiology

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In the past 20 yr, force transmission via connective tissue linkages at the muscle belly surface, called epimuscular myofascial force transmission, has been studied extensively. In this article, the effects of epimuscular linkages under passive muscle conditions are reviewed. Several animal studies that included direct (invasive) measurements of force transmission have shown that different connective tissue structures serve as an epimuscular pathway and that these tissues have sufficient stiffness, especially at supraphysiological muscle lengths and relative positions, to transmit substantial passive forces (up to 15% of active optimal force). Exact values of lumped tissue stiffness for different connective tissue structures have not yet been estimated. Experiments using various imaging techniques (ultrasound, MRI, shear wave elastography) have yielded some, but weak, evidence of epimuscular myofascial force transmission for passive muscles in humans. At this point, the functional consequences of epimuscular pathways for muscle and joint mechanics in the intact body are still unknown. Potentially, however, these pathways may affect sensory feedback and, thereby, neuromuscular control. In addition, altered epimuscular force transmission in pathological conditions may also contribute to changes in passive range of joint motion.

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Mechanical Coupling Between Muscle-Tendon Units Reduces Peak Stresses

Cited by 29 publications

References 35 publications

Neuromechanical coupling within the human triceps surae and its consequence on individual force sharing strategies

Neuromechanical coupling within the human triceps surae and its consequence on individual force sharing strategies

Biplanar ultrasound investigation of in vivo Achilles tendon displacement non-uniformity

Significance of epimuscular myofascial force transmission under passive muscle conditions

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