scholarly journals Evidence of adaptations of locomotor neural drive in response to enhanced intermuscular connectivity between the triceps surae muscles of the rat

2017 ◽  
Vol 118 (3) ◽  
pp. 1677-1689 ◽  
Author(s):  
Michel Bernabei ◽  
Jaap H. van Dieën ◽  
Huub Maas
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Muscle Activation ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Connective Tissues ◽  
Muscle Belly ◽  
The Central Nervous System ◽  
Triceps Surae Muscles ◽  
Gastrocnemius Muscles

The aims of this study were to investigate changes 1) in the coordination of activation of the triceps surae muscle group, and 2) in muscle belly length of soleus (SO) and lateral gastrocnemius (LG) during locomotion (trotting) in response to increased stiffness of intermuscular connective tissues in the rat. We measured muscle activation and muscle belly lengths, as well as hindlimb kinematics, before and after an artificial enhancement of the connectivity between SO and LG muscles obtained by implanting a tissue-integrating surgical mesh at the muscles’ interface. We found that SO muscle activation decreased to 62%, while activation of LG and medial gastrocnemius muscles increased to 134 and 125%, respectively, compared with the levels measured preintervention. Although secondary additional or amplified activation bursts were observed with enhanced connectivity, the primary pattern of activation over the stride and the burst duration were not affected by the intervention. Similar muscle length changes after manipulation were observed, suggesting that length feedback from spindle receptors within SO and LG was not affected by the connectivity enhancement. We conclude that peripheral mechanical constraints given by morphological (re)organization of connective tissues linking synergists are taken into account by the central nervous system. The observed shift in activity toward the gastrocnemius muscles after the intervention suggests that these larger muscles are preferentially recruited when the soleus has a similar mechanical disadvantage in that it produces an unwanted flexion moment around the knee. NEW & NOTEWORTHY Connective tissue linkages between muscle-tendon units may act as an additional mechanical constraint on the musculoskeletal system, thereby reducing the spectrum of solutions for performing a motor task. We found that intermuscular coordination changes following intermuscular connectivity enhancement. Besides showing that the extent of such connectivity is taken into account by the central nervous system, our results suggest that recruitment of triceps surae muscles is governed by the moments produced at the ankle-knee joints.

scholarly journals Multi- and Single-Joint Resistance Exercises Promote Similar Plantar Flexor Activation in Resistance Trained Men

2020 ◽  
Vol 17 (24) ◽  
pp. 9487
Author(s):  
Paulo Gentil ◽  
Daniel Souza ◽  
Murillo Santana ◽  
Rafael Ribeiro Alves ◽  
Mário Hebling Campos ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Negative Impact ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Plantar Flexors ◽  
Lateral Gastrocnemius ◽  
Leg Press ◽  
Electromyographic Signal ◽  
Triceps Surae Muscles ◽  
Gastrocnemius Muscles

The present study aimed to compare soleus, lateral, and medial gastrocnemius muscles activation during leg press and calf raise exercises in trained men. The study involved 22 trained men (27.1 ± 3.6 years, 82.7 ± 6.6 kg, 177.5 ± 5.2 cm, 3.6 ± 1.4 experience years) who performed one set of each exercise using a 10-repetition maximum (10RM) load in a counterbalanced randomized order and separated by 10 min of rest. The electromyographic signal was measured for the three major plantar flexors: soleus, medial, and lateral gastrocnemius. A comparison between exercises showed that the mean adjusted by peak values during the leg press were 49.20% for the gastrocnemius lateralis, 51.31% for the gastrocnemius medialis, and 50.76% for the soleus. Values for calf raise were 50.70%, 52.19%, and 51.34% for the lateral, medial gastrocnemius, and soleus, respectively. There were no significant differences between exercises for any muscle (lateral gastrocnemius (p = 0.230), medial gastrocnemius (p = 0.668), and soleus (p = 0.535)). The present findings suggest that both leg press and calf raises can be used with the purpose to recruit triceps surae muscles. This bring the suggestion that one can chose between exercises based on personal preferences and practical aspects, without any negative impact on muscle activation.

scholarly journals Increases in corticospinal responsiveness during a sustained submaximal plantar flexion

2009 ◽  
Vol 107 (1) ◽  
pp. 112-120 ◽  
Author(s):  
B. W. Hoffman ◽  
T. Oya ◽  
T. J. Carroll ◽  
A. G. Cresswell
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Plantar Flexion ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Task Failure ◽  
Submaximal Contraction

Studying the responsiveness of specific central nervous system pathways to electrical or magnetic stimulation can provide important information regarding fatigue processes in the central nervous system. We investigated the changes in corticospinal responsiveness during a sustained submaximal contraction of the triceps surae. Comparisons were made between the size of motor-evoked potentials (MEPs) elicited by motor cortical stimulation and cervicomedullary motor-evoked potentials (CMEPs) elicited by magnetic stimulation of the descending tracts to determine the site of any change in corticospinal responsiveness. Participants maintained an isometric contraction of triceps surae at 30% of maximal voluntary contraction (MVC) for as long as possible on two occasions. Stimulation was applied to the motor cortex or the cervicomedullary junction at 1-min intervals during contraction until task failure. Peripheral nerve stimulation was also applied to evoke maximal M waves (Mmax) and a superimposed twitch. Additionally, MEPs and CMEPs were evoked during brief contractions at 80%, 90%, and 100% of MVC as a nonfatigue control. During the sustained contractions, MEP amplitude increased significantly in soleus (113%) and medial gastrocnemius (108%) muscles and, at task failure, matched MEP amplitude in the prefatigue MVC (∼20–25% Mmax). In contrast, CMEP amplitude increased significantly in medial gastrocnemius (51%), but not in soleus (63%) muscle and, at task failure, was significantly smaller than during prefatigue MVC (5–6% Mmax vs. 11–13% Mmax). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness during sustained submaximal contraction of triceps surae.

scholarly journals Effects of muscle action type on corticospinal excitability and triceps surae muscle-tendon mechanics

2018 ◽  
Vol 119 (2) ◽  
pp. 563-572 ◽  
Author(s):  
P. Valadão ◽  
S. Kurokawa ◽  
T. Finni ◽  
J. Avela
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Motor Control ◽  
Pennation Angle ◽  
H Reflex ◽  
Corticospinal Excitability ◽  
Triceps Surae ◽  
Fascicle Length ◽  
The Central Nervous System ◽  
Muscle Actions

This study investigated whether the specific motor control strategy reported for eccentric muscle actions is dependent on muscle mechanical behavior. Motor evoked potentials, Hoffman reflex (H-reflex), fascicle length, pennation angle, and fascicle velocity of soleus muscle were compared between isometric and two eccentric conditions. Ten volunteers performed maximal plantarflexion trials in isometric, slow eccentric (25°/s), and fast eccentric (100°/s) conditions, each in a different randomized testing session. H-reflex normalized by the preceding M wave (H/M) was depressed in both eccentric conditions compared with isometric ( P < 0.001), while no differences in fascicle length and pennation angle were found among conditions. Furthermore, although the fast eccentric condition had greater fascicle velocity than slow eccentric ( P = 0.001), there were no differences in H/M. There were no differences in motor evoked potential size between conditions, and silent period was shorter for both eccentric conditions compared with isometric ( P = 0.009). Taken together, the present results corroborate the hypothesis that the central nervous system has an unique activation strategy during eccentric muscle actions and suggest that sensory feedback does not play an important role in modulating these muscle actions. NEW & NOTEWORTHY The present study provides new insight into the motor control of eccentric muscle actions. It was demonstrated that task-dependent corticospinal excitability modulation does not seem to depend on sensory information processing. These findings support the hypothesis that the central nervous system has a unique activation strategy during eccentric muscle actions.

scholarly journals Controlling Physical Interactions: Humans Do Not Minimize Muscle Effort

2017 ◽  
Author(s):  
Ryan Koeppen ◽  
Meghan E. Huber ◽  
Dagmar Sternad ◽  
Neville Hogan
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Muscle Activation ◽  
Tangential Velocity ◽  
Physical Interaction ◽  
Constrained Motion ◽  
Muscle Activation Patterns ◽  
The Central Nervous System ◽  
Physical Interactions ◽  
Muscular Effort

Physical interaction with tools is ubiquitous in functional activities of daily living. While tool use is considered a hallmark of human behavior, how humans control such physical interactions is still poorly understood. When humans perform a motor task, it is commonly suggested that the central nervous system coordinates the musculo-skeletal system to minimize muscle effort. In this paper, we tested if this notion holds true for motor tasks that involve physical interaction. Specifically, we investigated whether humans minimize muscle forces to control physical interaction with a circular kinematic constraint. Using a simplified arm model, we derived three predictions for how humans should behave if they were minimizing muscular effort to perform the task. First, we predicted that subjects would exert workless, radial forces on the constraint. Second, we predicted that the muscles would be deactivated when they could not contribute to work. Third, we predicted that when moving very slowly along the constraint, the pattern of muscle activity would not differ between clockwise (CW) and counterclockwise (CCW) motions. To test these predictions, we instructed human subjects to move a robot handle around a virtual, circular constraint at a constant tangential velocity. To reduce the effect of forces that might arise from incomplete compensation of neuro-musculo-skeletal dynamics, the target tangential speed was set to an extremely slow pace (∼1 revolution every 13.3 seconds). Ultimately, the results of human experiment did not support the predictions derived from our model of minimizing muscular effort. While subjects did exert workless forces, they did not deactivate muscles as predicted. Furthermore, muscle activation patterns differed between CW and CCW motions about the constraint. These findings demonstrate that minimizing muscle effort is not a significant factor in human performance of this constrained-motion task. Instead, the central nervous system likely prioritizes reducing other costs, such as computational effort, over muscle effort to control physical interactions.

Muscle activation and its distribution within human triceps surae muscles

2005 ◽  
Vol 99 (3) ◽  
pp. 1149-1156 ◽  
Author(s):  
Ryuta Kinugasa ◽  
Yasuo Kawakami ◽  
Tetsuo Fukunaga
Keyword(s):  
Muscle Activation ◽  
Spin Echo ◽  
Region Of Interest ◽  
Transverse Relaxation Time ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Active Muscle ◽  
Percentage Area ◽  
The Mean ◽  
Triceps Surae Muscles

The purposes of this study were 1) to quantify the volume of activated parts within a whole muscle and 2) to examine activated area distributions along the length of muscle. Seven male subjects performed five sets of 10 repetitions of a single-leg calf-raise exercise with the knee fully extended. Transverse relaxation time (T2)-weighted spin echo images were acquired before and immediately after the exercise. A range of pixels with a T2 greater than the mean +1 SD of the region of interest (ROI) from the preexercise image and pixels with a T2 lower than the mean + SD of the ROI from the postexercise image were defined as “active” muscle. The active muscle images were three dimensionally reconstructed, from which the volume of the activated muscle was determined for individual triceps surae (TS) muscles. Our data indicate that ∼46% of the medial gastrocnemius (MG) muscle was activated during the exercise, with activation of the lateral gastrocnemius (LG) and soleus (Sol) muscles being ∼35%. In the MG, distal portions had a greater percentage area of activated muscle than the proximal portions ( P < 0.05), which was consistent with the results regarding electromyogram activity. In contrast, regional activation differences were not observed in the LG and Sol. These findings suggest that the amounts of activated muscle and its distribution would be different among TS muscles.

scholarly journals Benefit of a single simulated hypobaric hypoxia in healthy mice performance and analysis of mitochondria-related gene changes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fei-Fei Wu ◽  
Kun-Long Zhang ◽  
Zheng-Mei Wang ◽  
Yi Yang ◽  
Shao-Hua Li ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Hypobaric Hypoxia ◽  
Video Tracking ◽  
Mild Stress ◽  
Behavioral Tests ◽  
Related Gene ◽  
Severe Hypobaric Hypoxia ◽  
The Central Nervous System ◽  
Gastrocnemius Muscles

AbstractSimulated hypobaric hypoxia (SHH) training has been used to enhance running performance. However, no studies have evaluated the effects of a single SHH exposure on healthy mice performance and analyzed the changes of mitochondria-related genes in the central nervous system. The current study used a mouse decompression chamber to simulate mild hypobaric hypoxia at the high altitude of 5000 m or severe hypobaric hypoxia at 8000 m for 16 h (SHH5000 & SHH8000, respectively). Then, the mouse behavioral tests were recorded by a modified Noldus video tracking. Third, the effects of SHH on 8 mitochondria-related genes of Drp1, Mfn1, Mfn2, Opa1, TFAM, SGK1, UCP2 and UCP4, were assessed in cerebellum, hippocampus and gastrocnemius muscles. The results have shown that a single mild or severe HH improves healthy mice performance. In cerebellum, 6 of all 8 detected genes (except Mfn2 and UCP4) did not change after SHH. In hippocampus, all detected genes did not change after SHH. In muscles, 7 of all 8 detected genes (except Opa1) did not change after SHH. The present study has indicated the benefit of a single SHH in healthy mice performance, which would due to the stabilized mitochondria against a mild stress state.

Neural Compensation Within the Human Triceps Surae During Prolonged Walking

2011 ◽  
Vol 105 (2) ◽  
pp. 548-553 ◽  
Author(s):  
Neil J. Cronin ◽  
Jussi Peltonen ◽  
Thomas Sinkjaer ◽  
Janne Avela
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Neural Activation ◽  
Fascicle Length ◽  
Muscle Fascicle ◽  
Compound Action Potentials ◽  
Triceps Surae Muscles ◽  
Short Time

During human walking, muscle activation strategies are approximately constant across consecutive steps over a short time, but it is unknown whether they are maintained over a longer duration. Prolonged walking may increase tendinous tissue (TT) compliance, which can influence neural activation, but the neural responses of individual muscles have not been investigated. This study investigated the hypothesis that muscle activity is up- or down-regulated in individual triceps surae muscles during prolonged walking. Thirteen healthy subjects walked on a treadmill for 60 min at 4.5 km/h, while triceps surae muscle activity, maximal muscle compound action potentials, and kinematics were recorded every 5 min, and fascicle lengths were estimated at the beginning and end of the protocol using ultrasound. After 1 h of walking, soleus activity increased by 9.3 ± 0.2% ( P < 0.05) and medial gastrocnemius activity decreased by 9.3 ± 0.3% ( P < 0.01). Gastrocnemius fascicle length at ground contact shortened by 4.45 ± 0.99% ( P < 0.001), whereas soleus fascicle length was unchanged ( P = 0.988). Throughout the stance phase, medial gastrocnemius fascicle lengthening decreased by 44 ± 13% ( P < 0.001), whereas soleus fascicle lengthening amplitude was unchanged ( P = 0.650). The data suggest that a compensatory neural strategy exists between triceps surae muscles and that changes in muscle activation are generally mirrored by changes in muscle fascicle length. These findings also support the notion of muscle-specific changes in TT compliance after prolonged walking and highlight the ability of the CNS to maintain relatively constant movement patterns in spite of neuromechanical changes in individual muscles.

scholarly journals Cosine tuning determines plantarflexors' activities during human upright standing and is affected by incomplete spinal cord injury

2020 ◽  
Author(s):  
Kai Lon Fok ◽  
Jae W Lee ◽  
Janelle Unger ◽  
Katherine Chan ◽  
Daichi Nozaki ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Spinal Cord Injury ◽  
Nervous System ◽  
Knee Extension ◽  
Medial Gastrocnemius ◽  
Quiet Standing ◽  
Incomplete Spinal Cord Injury ◽  
Cord Injury ◽  
The Central Nervous System

Plantarflexors such as the soleus (SOL) and medial gastrocnemius (MG) play key roles in controlling bipedal stance; however, how the central nervous system controls the activation levels of these plantarflexors is not well understood. Here we investigated how the central nervous system controls the plantarflexors' activation level during quiet standing in a cosine tuning manner where the maximal activation is achieved in a preferred direction (PD). Further, we investigated how spinal cord injury affects these plantarflexors' activations. Thirteen healthy adults (AB) and thirteen individuals with chronic, incomplete spinal cord injury (iSCI) performed quiet standing trials. Their body kinematics, kinetics as well as electromyography signals from the MG and SOL were recorded. In the AB-group, we found that the plantarflexors followed the cosine tuning manner during quiet standing. That is, MG was most active when the ratio of plantarflexion torque to knee extension torque was approximately 2:-3, while SOL was most active when the ratio was approximately 2:1. This suggests that the SOL muscle despite being a monoarticular muscle is sensitive to both ankle plantarflexion and knee extension during quiet standing. The difference in the PDs accounts for the phasic activity of MG and for the tonic activity of SOL. Unlike the AB-group, the MG's activity was similar to the SOL's activity in the iSCI-group, and the SOL PDs were similar to the ones in the AB-group. This result suggests that chronic iSCI affects the control strategy, i.e., cosine tuning, for MG, which may affect standing balance in individuals with iSCI.

scholarly journals Changes in muscle spindle firing in response to length changes of neighboring muscles

2016 ◽  
Vol 115 (6) ◽  
pp. 3146-3155 ◽  
Author(s):  
Hiltsje A. Smilde ◽  
Jake A. Vincent ◽  
Guus C. Baan ◽  
Paul Nardelli ◽  
Johannes C. Lodder ◽  
...  
Keyword(s):  
Muscle Spindle ◽  
Muscle Spindles ◽  
Triceps Surae ◽  
Connective Tissues ◽  
Muscle Belly ◽  
Intact Muscle ◽  
Muscle Compartment ◽  
Synergistic Muscles ◽  
Length Changes ◽  
Triceps Surae Muscles

Skeletal muscle force can be transmitted to the skeleton, not only via its tendons of origin and insertion but also through connective tissues linking the muscle belly to surrounding structures. Through such epimuscular myofascial connections, length changes of a muscle may cause length changes within an adjacent muscle and hence, affect muscle spindles. The aim of the present study was to investigate the effects of epimuscular myofascial forces on feedback from muscle spindles in triceps surae muscles of the rat. We hypothesized that within an intact muscle compartment, muscle spindles not only signal length changes of the muscle in which they are located but can also sense length changes that occur as a result of changing the length of synergistic muscles. Action potentials from single afferents were measured intra-axonally in response to ramp-hold release (RHR) stretches of an agonistic muscle at different lengths of its synergist, as well as in response to synergist RHRs. A decrease in force threshold was found for both soleus (SO) and lateral gastrocnemius afferents, along with an increase in length threshold for SO afferents. In addition, muscle spindle firing could be evoked by RHRs of the synergistic muscle. We conclude that muscle spindles not only signal length changes of the muscle in which they are located but also local length changes that occur as a result of changing the length and relative position of synergistic muscles.

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