Evidence of changes in load sharing during isometric elbow flexion with ramped torque

Bouillard, Killian; Nordez, Antoine; Hodges, Paul W.; Cornu, Christophe; Hug, François

doi:10.1016/j.jbiomech.2012.02.020

Cited by 53 publications

(76 citation statements)

References 30 publications

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“…But, the opposite changes in shear elastic modulus between knee extensors observed in several participants (Fig. 6) can be interpreted as changes in load sharing (3). Indeed, accounting for the relatively good repeatability of the shear elastic modulus measurements of the knee extensors at 25% of MVC, changes observed (e.g., ϩ90 kPa for rectus femoris in participant 2, Fig.…”

Section: Evidence Of Changes In Load Sharing (Experiments Ii)mentioning

confidence: 85%

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Shear elastic modulus can be used to estimate an index of individual muscle force during a submaximal isometric fatiguing contraction

Bouillard

Hug

Guével

et al. 2012

Journal of Applied Physiology

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The present study was designed to determine whether fatigue alters the ability to estimate an index of individual muscle force from shear elastic modulus measurements ( experiment I), and to test the ability of this technique to highlight changes in load sharing within a redundant muscle group during an isometric fatiguing task ( experiment II). Twelve subjects participated in experiment I, which consisted of smooth linear torque ramps from 0 to 80% of maximal voluntary contraction (MVC) performed before and after an isometric fatigue protocol, beginning at 40% of MVC and stopped when the force production dropped below 30% of MVC. Although the relationships between modulus and torque were very similar for pre- and postfatigue [root mean square deviation (RMSdeviation) = 3.7 ± 2.6% of MVC], the relationships between electromyography activity level and torque were greatly altered by fatigue (RMSdeviation = 10.3 ± 2.6% of MVC). During the fatiguing contraction, shear elastic modulus provided a significantly lower RMSdeviation between measured torque and estimated torque than electromyography activity level (5.7 ± 0.9 vs. 15.3 ± 3.8% of MVC). Experiment II performed with eight participants consisted of an isometric knee extension at 25% of MVC sustained until exhaustion. Opposite changes in shear elastic modulus were observed between synergists (vastus medialis, vastus lateralis, and rectus femoris) of some participants, reflecting changes in load sharing. In conclusion, despite the fact that we did not directly estimate muscle force (in Newtons), this is the first demonstration of an experimental technique to accurately quantify relative changes in force in an individual human muscle during a fatiguing contraction.

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Section: Evidence Of Changes In Load Sharing (Experiments Ii)mentioning

confidence: 85%

“…1). The shear elasticity map was chosen to be as large as possible, depending on the muscle depth/thickness (about from 1.0 ϫ 1.5 cm, for the abductor digiti minimi, and 1.5 ϫ 1.5 cm for the quadriceps muscles), to obtain a representative averaged shear elastic modulus value (3,4).…”

Section: Emgmentioning

confidence: 99%

Shear elastic modulus can be used to estimate an index of individual muscle force during a submaximal isometric fatiguing contraction

Bouillard

Hug

Guével

et al. 2012

Journal of Applied Physiology

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“…These linear relationships have provided the foundation of using muscle shear modulus measurements to estimate muscle 4 slack length (Koo et al, 2014;Maisetti et al, 2012), understand force sharing strategies during isometric contractions (Bouillard et al, 2014;Bouillard et al, 2012), and gain insight about motor adaptations during experimental muscle pain (Hug et al, 2014a;Hug et al, 2014b;Tucker et al, 2014). Emergence of these novel applications highlights the importance of understanding the physiological meaning of muscle shear modulus.…”

Section: Introductionmentioning

confidence: 99%

Factors that influence muscle shear modulus during passive stretch

Koo¹,

Hug²

2015

Journal of Biomechanics

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Although elastography has been increasingly used for evaluating muscle shear modulus associated with age, sex, musculoskeletal, and neurological conditions, its physiological meaning is largely unknown. This knowledge gap may hinder data interpretation, limiting the potential of using elastography to gain insights into muscle biomechanics in health and disease. We derived a mathematical model from a widely-accepted Hill-type passive force-length relationship to gain insight about the physiological meaning of resting shear modulus of skeletal muscles under passive stretching, and validated the model by comparing against the ex-vivo animal data reported in our recent work (Koo et al. 2013). The model suggested that resting shear modulus of a slack muscle is a function of specific tension and parameters that govern the normalized passive muscle force-length relationship as well as the degree of muscle anisotropy. The model also suggested that although the slope of the linear shear modulus-passive force relationship is primarily related to muscle anatomical cross-sectional area (i.e. the smaller the muscle cross-sectional area, the more the increase in shear modulus to result in the same passive muscle force), it is also governed by the normalized passive muscle force-length relationship and the degree of muscle anisotropy. Taken together, although muscle shear modulus under passive stretching has a strong linear relationship with passive muscle force, its actual value appears to be affected by muscle's mechanical, material, and architectural properties. This should be taken into consideration when interpreting the muscle shear modulus values.

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“…Second, we investigated the effect of prefatiguing VL on the changes of load sharing that occurred throughout a sustained contraction performed until task failure. Shear wave elastography was used to measure muscle shear elastic modulus, as this is considered to be an index of individual muscle force (Bouillard et al 2011(Bouillard et al , 2012a(Bouillard et al , 2012b. We hypothesized that 1) localized fatigue on VL would induce a systematic decrease in the force produced by this muscle, compensated by an increase in the force produced by the other extensors, and 2) fatigue on VL would lead to similar changes in load sharing between individuals during the sustained fatiguing contraction, suggesting a common compensation strategy.…”

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Effect of vastus lateralis fatigue on load sharing between quadriceps femoris muscles during isometric knee extensions

Bouillard

Jubeau

Nordez

et al. 2014

Journal of Neurophysiology

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The present study aimed to investigate the effects of selective fatigue (i.e., one muscle of the quadriceps) on load sharing strategies during submaximal knee extensions. Shear wave elastography was used to measure muscle shear elastic modulus, as this is considered to be an index of individual muscle force. Sixteen participants attended two experimental sessions that each involved six 10-s knee extensions at 20% of maximal voluntary contraction (MVC) followed by a sustained submaximal isometric knee extension at 20% of MVC, until task failure (Tlim). Between the 10-s contractions and Tlim, participants were required to rest (5 min) for the control session or underwent 5 min of electromyostimulation (EMS) on vastus lateralis (EMS session). Compared with the control session, vastus lateralis shear elastic modulus values were significantly lower after EMS considering both the start of Tlim (54.6 ± 11.8 vs. 68.4 ± 19.2 kPa; P = 0.011) and the entire Tlim contraction (59.0 ± 14.0 vs. 74.4 ± 20.3 kPa; P = 0.019). However, no significant differences were observed for the other recorded muscles (vastus medialis and rectus femoris; both P = 1), i.e., different patterns of changes were found between participants. In conclusion, this study demonstrates that prefatiguing a single agonist muscle does not lead to a consistent redistribution of load sharing among the quadriceps muscles between individuals. These results suggest that the central nervous system does not use a common principle among individuals to control load sharing when neuromuscular fatigue occurs.

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Evidence of changes in load sharing during isometric elbow flexion with ramped torque

Cited by 53 publications

References 30 publications

Shear elastic modulus can be used to estimate an index of individual muscle force during a submaximal isometric fatiguing contraction

Shear elastic modulus can be used to estimate an index of individual muscle force during a submaximal isometric fatiguing contraction

Factors that influence muscle shear modulus during passive stretch

Effect of vastus lateralis fatigue on load sharing between quadriceps femoris muscles during isometric knee extensions

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