Differential contributions of ankle plantarflexors during submaximal isometric muscle action: A PET and EMG study

Masood, Tahir; Bojsen‐Møller, Jens; Kalliokoski, Kari K.; Kirjavainen, Anna; Äärimaa, Ville; Magnusson, S. Peter; Finni, Taija

doi:10.1016/j.jelekin.2014.03.002

Cited by 31 publications

(27 citation statements)

References 30 publications

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“…All these results are in line with our results showing on average a two times higher activation of the GM than the GL during the isometric plantarflexion at 20% of MVC. In the present study, the SOL exhibited a slightly greater activation level than both the GM and GL, which is consistent with results from Mademli and Arampatzis (2005), but inconsistent with those of Cresswell et al (1995) and Masood et al (2014), all being performed during isometric submaximal tasks but in varying positions. Note that an activation biased toward the SOL muscle, which exhibits both the biggest PCSA and the highest slow-twitch fibre content, may reduce the metabolic cost of the contraction at low contraction intensity, as discussed below.…”

Section: Distribution Of Muscle Activationsupporting

confidence: 78%

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: Distribution Of Muscle Activationsupporting

confidence: 78%

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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“…These three muscles may also be activated to different relative levels at any given joint torque. Indeed, activation of the lateral gastrocnemius muscle was shown to be relatively low at 30% of maximum voluntary plantarflexion contraction compared with that of the medial gastrocnemius (Masood et al, 2014). This highlights the complexity of loading on the Achilles tendon with contributions from three independent muscles, which have been suggested to constitute mechanically separate tendon compartments within the Achilles (Bojsen-Moller and Magnusson, 2015).…”

Section: Discussionmentioning

confidence: 95%

Is human Achilles tendon deformation greater in regions where cross-sectional area is smaller?

Reeves

Cooper

2017

Journal of Experimental Biology

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The Achilles is a long tendon varying in cross-sectional area (CSA) considerably along its length. For the same force, a smaller CSA would experience higher tendon stress and we hypothesised that these areas would therefore undergo larger transverse deformations. A novel magnetic resonance imaging-based approach was implemented to quantify changes in tendon CSA from rest along the length of the Achilles tendon under load conditions corresponding to 10%, 20% and 30% of isometric plantar flexor maximum voluntary contraction (MVC). Reductions in tendon CSA occurring during contraction from the resting condition were assumed to be proportional to the longitudinal elongations within those regions (Poisson's ratio). Rather than tendon regions of smallest CSA undergoing the greatest deformations, the outcome was region specific, with the proximal (gastrocnemius) tendon portion showing larger transverse deformations upon loading compared with the distal portion of the Achilles (P<0.01). Transverse tendon deformation only occurred in selected regions of the distal Achilles tendon at 20% and 30% of MVC, but in contrast occurred throughout the proximal portion of the Achilles at all contraction levels (10%, 20% and 30% of MVC; P<0.01). Calculations showed that force on the proximal tendon portion was ∼60% lower, stress ∼70% lower, stiffness ∼30% lower and Poisson's ratio 6-fold higher compared with those for the distal portion of the Achilles tendon. These marked regional differences in mechanical properties may allow the proximal portion to function as a mechanical buffer to protect the stiffer, more highly stressed, distal portion of the Achilles tendon from injury.

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“…There are known structural and material changes with age in muscle ; indices derived from the SR tensor could potentially be used as imaging biomarkers of these changes. During submaximal isometric muscle contraction, the medial gastrocnemius (MG) has been identified to display the highest activity (in terms of % electromyography) as well as highest glucose uptake (using positron emission tomography) . These results indicate that the MG is heavily involved in submaximal isometric muscle contraction.…”

Section: Introductionmentioning

confidence: 96%

Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: Potential index of lateral force transmission

et al. 2014

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Purpose The strain rate (SR) tensor measures the principal directions and magnitude of the instantaneous deformation; this study aims to track age related changes in the 2D SR tensor in the medial gastrocnemius during passive joint rotation and active isometric contraction. Methods SR tensors were derived from velocity encoded magnetic resonance phase-contrast images in nine young (28 yrs) and eight senior (78 yrs) women. Strain rates along and in the cross-section of the fiber were calculated from the SR tensor and used to derive the out-plane SR. Age related and regional differences in the SR eigenvalues, orientation, and the angle between the SR and muscle fiber (SR-fiber angle) were statistically analyzed. Results SR along the fiber was significantly different between the cohorts during isometric contraction with higher values in the young (P<0.05). The SR-fiber angle was larger in the young for both motion types but this difference was not statistically significant. Significant regional differences in the SR indices was seen in passive joint rotation (P<0.05) for both cohorts. Conclusion SR mapping reflects age related and regional differences during active and passive motion respectively; this may arise from differences in contractility (active motion) and elastic properties (active and passive motion).

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Differential contributions of ankle plantarflexors during submaximal isometric muscle action: A PET and EMG study

Cited by 31 publications

References 30 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

Is human Achilles tendon deformation greater in regions where cross-sectional area is smaller?

Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: Potential index of lateral force transmission

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