scholarly journals Tuning of feedforward control enables stable muscle force-length dynamics after loss of autogenic proprioceptive feedback

2019 ◽  
Author(s):  
JC Gordon ◽  
NC Holt ◽  
AA Biewener ◽  
MA Daley
Keyword(s):  
Feedforward Control ◽  
Control Mechanisms ◽  
Uneven Terrain ◽  
Leg Muscles ◽  
Numida Meleagris ◽  
Muscle Dynamics ◽  
Ankle Kinematics ◽  
Intact Muscle

AbstractAnimals must integrate feedforward, feedback and intrinsic mechanical control mechanisms to maintain stable locomotion. Recent studies of guinea fowl (Numida meleagris) revealed that the distal leg muscles rapidly modulate force and work output to minimize perturbations in uneven terrain. Here we probe the role of reflexes in the rapid perturbation response of muscle by studying the effects of proprioceptive loss. We induced bilateral loss of autogenic proprioception in the lateral gastrocnemius muscle (LG) using self-reinnervation. We compared ankle kinematics and in vivo muscle dynamics in birds with reinnervated LG and intact LG. Reinnervated and intact muscles exhibit similar force-length dynamics, with rapid changes in work to stabilize running obstacle terrain. Reinnervated LG exhibits 23ms earlier steady-state activation, consistent with feedforward tuning of activation phase to compensate for lost proprioception. Modulation of force duration is impaired in rLG, confirming the role of reflex feedback in regulating force duration in intact muscle.

scholarly journals Tuning of feedforward control enables stable muscle force-length dynamics after loss of autogenic proprioceptive feedback

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Joanne C Gordon ◽  
Natalie C Holt ◽  
Andrew Biewener ◽  
Monica A Daley
Keyword(s):  
Steady State ◽  
Feedforward Control ◽  
Control Mechanisms ◽  
Leg Muscles ◽  
Similar Work ◽  
Numida Meleagris ◽  
Muscle Dynamics ◽  
Intact Muscle

Animals must integrate feedforward, feedback and intrinsic mechanical control mechanisms to maintain stable locomotion. Recent studies of guinea fowl (Numida meleagris) revealed that the distal leg muscles rapidly modulate force and work output to minimize perturbations in uneven terrain. Here we probe the role of reflexes in the rapid perturbation responses of muscle by studying the effects of proprioceptive loss. We induced bilateral loss of autogenic proprioception in the lateral gastrocnemius muscle (LG) using self-reinnervation. We compared in vivo muscle dynamics and ankle kinematics in birds with reinnervated and intact LG. Reinnervated and intact LG exhibit similar steady state mechanical function and similar work modulation in response to obstacle encounters. Reinnervated LG exhibits 23ms earlier steady-state activation, consistent with feedforward tuning of activation phase to compensate for lost proprioception. Modulation of activity duration is impaired in rLG, confirming the role of reflex feedback in regulating force duration in intact muscle.

Relationship of Motor Mechanisms to Gastroparesis Symptoms: Towards Individualized Treatment

2021 ◽  
Author(s):  
Michael Camilleri
Keyword(s):  
Animal Studies ◽  
Gastrointestinal Symptoms ◽  
Feedback Regulation ◽  
Individualized Treatment ◽  
Control Mechanisms ◽  
Gastric Accommodation ◽  
Billroth I ◽  
Gastric Sensitivity

Following a classical paper by Dr. Keith A. Kelly published in this journal, and over the past 40 years, there has been increased understanding of the functions of different regions of the stomach, specifically the fundus, antrum, and pylorus. Several of the important physiological principles were based on in vivo animal studies that led to the appreciation of regional function and control mechanisms. These include the roles of the extrinsic parasympathetic vagal innervation, the gastric enteric nervous system and electrical syncytium consisting of pacemaker cells and smooth muscle cells, and duodenogastric reflexes providing feedback regulation following the arrival of food and hydrogen ions stimulating the release of hormones and vagal afferent mechanisms that inhibit gastric motility and stimulate pyloric contractility. Further insights on the role of regional motor functions in gastric emptying were obtained from observations in patients following diverse gastric surgeries or bariatric procedures, including fundoplication, Billroth I and sleeve gastrectomy, and sleeve gastroplasty. Antropyloroduodenal manometry as well as measurements of pyloric diameter and distensibility index provided important assessments of the role of antral hypomotility and pylorospasm, and these constitute specific targets for individualized treatment of patients with gastroparesis. Moreover, in patients with upper gastrointestinal symptoms suggestive of gastroparesis, the availability of measurements of gastric accommodation as well as pharmacological agents to reduced gastric sensitivity or enhance gastric accommodation provide additional specific targets for individualized treatment. It is anticipated that, in the future, such physiological measurements will be applied in patients to optimize choice of therapy, possibly including identifying the best candidate for pyloric interventions.

Relationship of intracellular creatine concentration and uptake to muscle mass in vivo

1978 ◽  
Vol 235 (5) ◽  
pp. C199-C203 ◽  
Author(s):  
W. W. Hofmann ◽  
J. Butte ◽  
H. A. Leon
Keyword(s):  
Isometric Exercise ◽  
Major Change ◽  
Creatine Phosphate ◽  
Control Mechanisms ◽  
Relationship Of ◽  
Developing Muscle ◽  
Hydrolysis Of

Attempts have been made to evaluate the role of intracellular creatine in conditions leading to increased or decreased amounts of contractile protein in rat skeletal muscles. Resting concentrations of intracellular creatine ([Cr]i) and creatine phosphate ([CrP]i) were compared in gastrocnemius and soleus muscles with those immediately after a 20-s tetanic stimulation. The hydrolysis of creatine phosphate was the same after heavily and lightly loaded contractions, suggesting that hypertrophy of isometric exercise is not mediated by creatine. With atrophy after denervation or interruption of sciatic axoplasmic flow [Cr]i also remained unchanged, though [CrP]i and the rate of Cr uptake fell after denervation. The major change in adult red and white muscle bulk with unaltered [Cr]i suggests that the Cr sensitivity found by others in developing muscle in vitro has been supplemented or replaced by other control mechanisms.

Nondominant Arm Advantages in Load Compensation During Rapid Elbow Joint Movements

2003 ◽  
Vol 90 (3) ◽  
pp. 1503-1513 ◽  
Author(s):  
Leia B. Bagesteiro ◽  
Robert L. Sainburg
Keyword(s):  
Muscle Activity ◽  
Considerable Increase ◽  
Feedforward Control ◽  
Elbow Flexion ◽  
Control Mechanisms ◽  
Final Position ◽  
Flexor Muscle ◽  
Load Compensation ◽  
Air Jet

This study was designed to examine interlimb asymmetries in responding to unpredictable changes in inertial loads, which have implications for our understanding of the neural mechanisms underlying handedness. Subjects made repetitive single joint speed constrained 20° elbow flexion movements, while the arm was supported on a horizontal, frictionless, air-jet system. On random trials, a 2-kg mass was attached to the arm splint prior to the “go” signal. Subjects were not given explicit information about the mass prior to movement nor were they able to view their limb or the mass. Accordingly, muscle activity, recorded prior to peak tangential finger acceleration, was the same for loaded and baseline trials. After this point, substantial changes in muscle activity occurred. In both limbs, the load compensation response was associated with a reduction in extensor muscle activity, resulting in a prolonged flexion phase of motion. For the nondominant arm, this resulted in effective load compensation, such that no differences in final position accuracy occurred between loaded and baseline trials. However, the dominant arm response also included a considerable increase in flexor muscle activity. This substantially prolonged the flexor acceleration phase of motion, relative to that of the nondominant arm. As a result, the dominant arm overcompensated the effects of the load, producing a large and systematic overshoot of final position. These results indicate more effective load compensation responses for the nondominant arm; supporting a specialized role of the nondominant arm/hemisphere system in sensory feedback mediated error correction mechanisms. The results also suggest that specialization of the dominant arm system for controlling limb and task dynamics is specifically related to feedforward control mechanisms.

scholarly journals Leg muscles that mediate stability: mechanics and control of two distal extensor muscles during obstacle negotiation in the guinea fowl

2011 ◽  
Vol 366 (1570) ◽  
pp. 1580-1591 ◽  
Author(s):  
Monica A. Daley ◽  
Andrew A. Biewener
Keyword(s):  
Muscle Activation ◽  
Critical Role ◽  
Body Height ◽  
Neuromuscular Control ◽  
Guinea Fowl ◽  
Fascicle Length ◽  
Uneven Terrain ◽  
Leg Muscles ◽  
And Control

Here, we used an obstacle treadmill experiment to investigate the neuromuscular control of locomotion in uneven terrain. We measured in vivo function of two distal muscles of the guinea fowl, lateral gastrocnemius (LG) and digital flexor-IV (DF), during level running, and two uneven terrains, with 5 and 7 cm obstacles. Uneven terrain required one step onto an obstacle every four to five strides. We compared both perturbed and unperturbed strides in uneven terrain to level terrain. When the bird stepped onto an obstacle, the leg became crouched, both muscles acted at longer lengths and produced greater work, and body height increased. Muscle activation increased on obstacle strides in the LG, but not the DF, suggesting a greater reflex contribution to LG. In unperturbed strides in uneven terrain, swing pre-activation of DF increased by 5 per cent compared with level terrain, suggesting feed-forward tuning of leg impedance. Across conditions, the neuromechanical factors in work output differed between the two muscles, probably due to differences in muscle–tendon architecture. LG work depended primarily on fascicle length, whereas DF work depended on both length and velocity during loading. These distal muscles appear to play a critical role in stability by rapidly sensing and responding to altered leg–ground interaction.

Myogenic reactivity and resistance distribution in the coronary arterial tree: a model study

2000 ◽  
Vol 278 (5) ◽  
pp. H1490-H1499 ◽  
Author(s):  
Annemiek J. M. Cornelissen ◽  
Jenny Dankelman ◽  
Ed VanBavel ◽  
Henk G. Stassen ◽  
Jos A. E. Spaan
Keyword(s):  
Maximum Effect ◽  
Myogenic Response ◽  
Control Mechanisms ◽  
Arterial Tree ◽  
Model Study ◽  
In Series ◽  
Myogenic Activity ◽  
And Control

The objectives of this study were to evaluate the myogenic behavior of blood vessels and their interaction within the coronary arterial tree and to evaluate the possible role of the myogenic response in autoregulation. The model consists of 10 compartments in series, each representing a class of vessel sizes. Diameter and resistance in each class are determined by their value at full dilation ( d p, R p) and by the myogenic response. Three distributions of R p and three distributions of myogenic strength, M i (slope of pressure-diameter curve, range −0.05 to −0.4%/mmHg) were evaluated (9 cases). It was found that larger vessels attenuate the myogenic activity of smaller vessels and that myogenic responsiveness is sufficient to achieve autoregulation. When M i has a maximum in vessels of 84 μm, the maximum effect of perfusion pressure on active diameter occurs in vessels between 123 and 181 μm, depending on the distribution of R p. Distribution of resistance and control mechanisms in the coronary arterial tree are important for interpretation of individual vessel responses as observed in vivo.

scholarly journals Adding carbon fiber to shoe soles may not improve running economy: a muscle-level explanation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Owen N. Beck ◽  
Pawel R. Golyski ◽  
Gregory S. Sawicki
Keyword(s):  
Carbon Fiber ◽  
Energy Expenditure ◽  
Bending Stiffness ◽  
Running Economy ◽  
Whole Body ◽  
Leg Muscles ◽  
Muscle Dynamics ◽  
Energy Consuming ◽  
Shoe Soles

Abstract In an attempt to improve their distance-running performance, many athletes race with carbon fiber plates embedded in their shoe soles. Accordingly, we sought to establish whether, and if so how, adding carbon fiber plates to shoes soles reduces athlete aerobic energy expenditure during running (improves running economy). We tested 15 athletes as they ran at 3.5 m/s in four footwear conditions that varied in shoe sole bending stiffness, modified by carbon fiber plates. For each condition, we quantified athlete aerobic energy expenditure and performed biomechanical analyses, which included the use of ultrasonography to examine soleus muscle dynamics in vivo. Overall, increased footwear bending stiffness lengthened ground contact time (p = 0.048), but did not affect ankle (p ≥ 0.060), knee (p ≥ 0.128), or hip (p ≥ 0.076) joint angles or moments. Additionally, increased footwear bending stiffness did not affect muscle activity (all seven measured leg muscles (p ≥ 0.146)), soleus active muscle volume (p = 0.538; d = 0.241), or aerobic power (p = 0.458; d = 0.04) during running. Hence, footwear bending stiffness does not appear to alter the volume of aerobic energy consuming muscle in the soleus, or any other leg muscle, during running. Therefore, adding carbon fiber plates to shoe soles slightly alters whole-body and calf muscle biomechanics but may not improve running economy.

scholarly journals Adding carbon fiber to shoe soles does not improve running economy: a muscle-level explanation

2020 ◽  
Author(s):  
Owen N. Beck ◽  
Pawel R. Golyski ◽  
Gregory S. Sawicki
Keyword(s):  
Carbon Fiber ◽  
Energy Expenditure ◽  
Bending Stiffness ◽  
Running Economy ◽  
Whole Body ◽  
Leg Muscles ◽  
Muscle Dynamics ◽  
Energy Consuming ◽  
Shoe Soles

AbstractIn an attempt to improve their distance-running performance, many athletes race with carbon fiber plates embedded in their shoe soles. Accordingly, we sought to establish whether, and if so how, adding carbon fiber plates to shoes soles reduces athlete aerobic energy expenditure during running (improves running economy). We tested 15 athletes during running at 3.5 m/s in four footwear conditions that varied in shoe sole carbon fiber plate bending stiffness. For each condition, we quantified athlete aerobic energy expenditure and performed biomechanics analyses, which included the use of ultrasound imaging to examine soleus muscle dynamics in vivo. Overall, increased footwear bending stiffness lengthened ground contact time (p=0.048), but did not affect ankle (p≥0.060), knee (p≥0.128), or hip (p≥0.076) joint angles or moments. Additionally, increased footwear bending stiffness did not affect muscle activity (all seven measured leg muscles (p≥0.146)), stride averaged active soleus volume, (p=0.068) or aerobic power (p=0.458) during running. Hence, footwear bending stiffness does not appear to alter the volume of aerobic energy consuming muscle in the soleus, or any other leg muscle, during running. Therefore, adding carbon fiber plates to shoe soles slightly alters whole-body and calf muscle biomechanics but does not improve running economy.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

Meiotic CENP-C is a shepherd: bridging the space between the centromere and the kinetochore in time and space

2020 ◽  
Vol 64 (2) ◽  
pp. 251-261
Author(s):  
Jessica E. Fellmeth ◽  
Kim S. McKim
Keyword(s):  
Chromosome Segregation ◽  
New Technologies ◽  
Early Prophase ◽  
Unique Role ◽  
Kinetochore Assembly ◽  
M Phase ◽  
In Vivo Analysis ◽  
Meiosis I

Abstract While many of the proteins involved in the mitotic centromere and kinetochore are conserved in meiosis, they often gain a novel function due to the unique needs of homolog segregation during meiosis I (MI). CENP-C is a critical component of the centromere for kinetochore assembly in mitosis. Recent work, however, has highlighted the unique features of meiotic CENP-C. Centromere establishment and stability require CENP-C loading at the centromere for CENP-A function. Pre-meiotic loading of proteins necessary for homolog recombination as well as cohesion also rely on CENP-C, as do the main scaffolding components of the kinetochore. Much of this work relies on new technologies that enable in vivo analysis of meiosis like never before. Here, we strive to highlight the unique role of this highly conserved centromere protein that loads on to centromeres prior to M-phase onset, but continues to perform critical functions through chromosome segregation. CENP-C is not merely a structural link between the centromere and the kinetochore, but also a functional one joining the processes of early prophase homolog synapsis to late metaphase kinetochore assembly and signaling.

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