Three‐dimensional topography of the motor endplates of the rat gastrocnemius muscle

Prodanov, Dimiter; Thil, Marie-Anne; Marani, Enrico; Delbeke, Jean; Holsheimer, J.

doi:10.1002/mus.20378

Cited by 23 publications

(21 citation statements)

References 29 publications

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“…MG and LG muscles consist of multiple compartments with multiple motor endplates [18], [19]. Bipolar intramuscular wire electrodes were inserted near motor endplates located in the distal region of MG and the proximal region of LG.…”

Section: Methodsmentioning

confidence: 99%

Three-Dimensional Ankle Moments and Nonlinear Summation of Rat Triceps Surae Muscles

et al. 2014

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The Achilles tendon and epimuscular connective tissues mechanically link the triceps surae muscles. These pathways may cause joint moments exerted by each muscle individually not to sum linearly, both in magnitude and direction. The aims were (i) to assess effects of sagittal plane ankle angle (varied between 150° and 70°) on isometric ankle moments, in both magnitude and direction, exerted by active rat triceps surae muscles, (ii) to assess ankle moment summation between those muscles for a range of ankle angles and (iii) to assess effects of sagittal plane ankle angle and muscle activation on Achilles tendon length. At each ankle angle, soleus (SO) and gastrocnemius (GA) muscles were first excited separately to assess ankle-angle moment characteristics and subsequently both muscles were excited simultaneously to investigate moment summation. The magnitude of ankle moment exerted by SO and GA, the SO direction in the transverse and sagittal planes, and the GA direction in the transverse plane were significantly affected by ankle angle. SO moment direction in the frontal and sagittal planes were significantly different from that of GA. Nonlinear magnitude summation varied between 0.6±2.9% and −3.6±2.9%, while the nonlinear direction summation varied between 0.3±0.4° and −0.4±0.7° in the transverse plane, between 0.5±0.4° and 0.1±0.4° in the frontal plane, and between 3.0±7.9° and 0.3±2.3° in the sagittal plane. Changes in tendon length caused by SO contraction were significantly lower than those during contraction of GA and GA+SO simultaneously. Thus, moments exerted by GA and SO sum nonlinearly both in the magnitude and direction. The limited degree of nonlinear summation may be explained by different mechanisms acting in opposite directions.

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Section: Methodsmentioning

confidence: 99%

Three-Dimensional Ankle Moments and Nonlinear Summation of Rat Triceps Surae Muscles

et al. 2014

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“…A reference electrode was inserted underneath the skin, in the region above the gluteus maximus muscle. Given the distribution of fiber type in SO and LG muscle regions (Armstrong and Phelps, 1984) and muscle architecture (Prodanov et al, 2005), the EMG pick-up area consisted of slow oxidative fibers in the SO and a majority of fast glycolytic fibers in the LG. Electrode placement was verified by stimulation through the implanted wires.…”

Section: Sensors Implantationmentioning

confidence: 99%

Longitudinal and transversal displacements between triceps surae muscles during locomotion of the rat

Bernabei

Dieën

Maas

2017

Journal of Experimental Biology

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The functional consequences of differential muscle activation and contractile behavior between mechanically coupled synergists are still poorly understood. Even though synergistic muscles exert similar mechanical effects at the joint they span, differences in the anatomy, morphology and neural drive may lead to non-uniform contractile conditions. This study aimed to investigate the patterns of activation and contractile behavior of triceps surae muscles, to understand how these contribute to the relative displacement between the one-joint soleus (SO) and two-joint lateral gastrocnemius (LG) muscle bellies and their distal tendons during locomotion in the rat. In seven rats, muscle belly lengths and muscle activation during level and upslope trotting were measured by sonomicrometry crystals and electromyographic electrodes chronically implanted in the SO and LG. Length changes of muscle-tendon units (MTUs) and tendon fascicles were estimated based on joint kinematics and muscle belly lengths. Distances between implanted crystals were further used to assess longitudinal and transversal deformations of the intermuscular volume between the SO and LG. For both slope conditions, we observed differential timing of muscle activation as well as substantial differences in contraction speeds between muscle bellies (maximal relative speed 55.9 mm s −1 ). Muscle lengths and velocities did not differ significantly between level and upslope locomotion, only EMG amplitude of the LG was affected by slope. Relative displacements between SO and LG MTUs were found in both longitudinal and transversal directions, yielding an estimated maximal length change difference of 2.0 mm between their distal tendons. Such relative displacements may have implications for the force exchanged via intermuscular and intertendinous pathways.

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“…However, SO muscle and its epimuscular myofascial connections were not affected. MG and LG muscles consist of multiple compartments with multiple motor endplates (De Ruiter et al, 1995;Prodanov et al, 2005). To excite these muscles, bipolar intramuscular wire electrodes were inserted near the motor endplates located in the distal region of MG and the proximal region of LG.…”

Section: Surgerymentioning

confidence: 99%

“…In addition, the electrodes were placed rather superficially within MG and LG muscle bellies, and submaximal stimulation was applied to make sure that only MG and LG muscle fibers were excited. As only one compartment of each MG and LG muscle was stimulated (De Ruiter et al, 1995;Prodanov et al, 2005), not all muscle fibers of these muscles were excited. A pilot experiment, in which excitation of LG and MG via nerve stimulation was compared with that via intramuscular stimulation, showed that approximately 20% of maximum active ankle moment exerted by MG and LG muscles fibers was exerted when stimulating intramuscularly (Tijs et al, 2014).…”

Section: Experimental Protocolmentioning

confidence: 99%

No functionally relevant mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors

Tijs

Dieën

Maas

2015

Journal of Experimental Biology

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Triceps surae muscles are mechanically connected by the shared Achilles tendon and by epimuscular myofascial connections. We aimed to assess the effects of proximal lengthening of gastrocnemius and plantaris muscles, imposed by changes in knee angle, on the magnitude and direction of the 3D ankle moment exerted by the soleus muscle and the mechanical interaction between ankle plantar flexor muscles during co-activation of gastrocnemius muscle, in the rat (N=9). Ankle angle was kept constant (90 deg), whereas knee angle was varied between 60 deg and 130 deg. At each knee angle, the soleus muscle was excited individually as well as simultaneously with the gastrocnemius muscle (SO+GA). The mathematical sum of individual soleus and gastrocnemius ankle moments was compared with the ankle moment exerted by SO+GA to assess nonlinear summation. Knee angle did not affect the magnitude of the soleus ankle moment (P=0.695). Moment directions in the transverse (P=0.050) and frontal (P=0.008) planes were affected by knee angle, but dissection indicated that this was not caused by length changes of the two-joint synergistic muscles. Nonlinear summation was found in the magnitude (−1.4±1.9%, mean±s.d., P<0.001) and in the frontal plane vector direction of the ankle moment (0.13±0.23 deg, P=0.003); however, the extent did not change with knee angle. Although contraction of SO+GA increased the length of the Achilles tendon compared with its length at rest, this was not dependent on the knee angle (P=0.649). Despite the fact that intermuscular force transmission per se cannot be excluded, we conclude that, in vivo, the mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors are not functionally relevant.

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Three‐dimensional topography of the motor endplates of the rat gastrocnemius muscle

Cited by 23 publications

References 29 publications

Three-Dimensional Ankle Moments and Nonlinear Summation of Rat Triceps Surae Muscles

Three-Dimensional Ankle Moments and Nonlinear Summation of Rat Triceps Surae Muscles

Longitudinal and transversal displacements between triceps surae muscles during locomotion of the rat

No functionally relevant mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors

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