Effect of acute inflation on the mechanics of the inspiratory muscles

2009 ◽  
Vol 107 (1) ◽  
pp. 315-323 ◽  
Author(s):  
André De Troyer ◽  
Theodore A. Wilson
Keyword(s):  
Adverse Effect ◽  
Muscle Activation ◽  
Muscle Force ◽  
Radius Of Curvature ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Respiratory Effect ◽  
Inspiratory Muscles ◽  
Generating Capacity ◽  
Very High

When the lung is inflated acutely, the capacity of the diaphragm to generate pressure, in particular pleural pressure (Ppl), is impaired because the muscle during contraction is shorter and generates less force. At very high lung volumes, the pressure-generating capacity of the diaphragm may be further reduced by an increase in the muscle radius of curvature. Lung inflation similarly impairs the pressure-generating capacity of the inspiratory intercostal muscles, both the parasternal intercostals and the external intercostals. In contrast to the diaphragm, however, this adverse effect is largely related to the orientation and motion of the ribs, rather than the ability of the muscles to generate force. During combined activation of the two sets of muscles, the change in Ppl is larger than during isolated diaphragm activation, and this added load on the diaphragm reduces the shortening of the muscle and increases muscle force. In addition, activation of the diaphragm suppresses the cranial displacement of the passive diaphragm that occurs during isolated intercostal contraction and increases the respiratory effect of the intercostals. As a result, the change in Ppl generated during combined diaphragm-intercostal activation is greater than the sum of the pressures generated during separate muscle activation. Although this synergistic interaction becomes particularly prominent at high lung volumes, lung inflation, either bilateral or unilateral, places a substantial stress on the inspiratory muscle pump.

scholarly journals Construct Validity of Muscle Force Tests of the Rotator Cuff Muscles: An Electromyographic Investigation

2010 ◽  
Vol 90 (4) ◽  
pp. 572-580 ◽  
Author(s):  
Rebecca L. Brookham ◽  
Linda McLean ◽  
Clark R. Dickerson
Keyword(s):  
Rotator Cuff ◽  
Muscle Activation ◽  
Muscle Force ◽  
Test Group ◽  
Clinical Test ◽  
Shoulder Muscles ◽  
Frequent Use ◽  
Medial Rotation ◽  
Generating Capacity ◽  
Teres Minor

Background Manual muscle tests (MMTs) are used in clinical settings to evaluate the function and strength (force-generating capacity) of a specific muscle in a position at which the muscle is believed to be most isolated from other synergists and antagonists. Despite frequent use of MMTs, few electromyographic evaluations exist to confirm the ability of MMTs to isolate rotator cuff muscles. Objective This study examined rotator cuff isolation during 29 shoulder muscle force tests (9 clinical and 20 generic tests). Design An experimental design was used in this study. Participants and Measurements Electromyographic data were recorded from 4 rotator cuff muscles and 10 additional shoulder muscles of 12 male participants. Maximal isolation ratios (mean specific rotator cuff muscle activation to mean activation of the other 13 recorded muscles) defined which of these tests most isolated the rotator cuff muscles. Results Three rotator cuff muscles were maximally isolated (obtained highest isolation ratios) within their respective clinical test groups (lateral rotator test group for the infraspinatus and teres minor muscles and abduction test group for the supraspinatus muscle). The subscapularis muscle was maximally isolated equally as effectively within the generic ulnar force and clinical medial rotation groups. Similarly, the supraspinatus and teres minor muscles were isolated equally as effectively in some generic test groups as they were in their respective clinical test groups. Limitations Postural artifact in the wire electrodes caused exclusion of some channels from calculations. The grouping of muscle force tests based on test criteria (clinical or generic tests and muscle action) may have influenced which groups most isolated the muscle of interest. Conclusions The results confirmed the appropriateness of 9 commonly used clinical tests for isolating rotator cuff muscles, but suggested that several other muscle force tests were equally appropriate for isolating these muscles.

scholarly journals The effects of 12 weeks of static stretch training on the functional, mechanical, and architectural characteristics of the triceps surae muscle–tendon complex

2021 ◽  
Author(s):  
Stefano Longo ◽  
Emiliano Cè ◽  
Angela Valentina Bisconti ◽  
Susanna Rampichini ◽  
Christian Doria ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Muscle Stiffness ◽  
Triceps Surae ◽  
Maximum Force ◽  
Passive Stiffness ◽  
Electromechanical Delay ◽  
Fascicle Length ◽  
Generating Capacity ◽  
Plantarflexor Muscles

Abstract Purpose We investigated the effects of 12 weeks of passive static stretching training (PST) on force-generating capacity, passive stiffness, muscle architecture of plantarflexor muscles. Methods Thirty healthy adults participated in the study. Fifteen participants (STR, 6 women, 9 men) underwent 12-week plantarflexor muscles PST [(5 × 45 s-on/15 s-off) × 2exercises] × 5times/week (duration: 2250 s/week), while 15 participants (CTRL, 6 women, 9 men) served as control (no PST). Range of motion (ROM), maximum passive resistive torque (PRTmax), triceps surae architecture [fascicle length, fascicle angle, and thickness], passive stiffness [muscle–tendon complex (MTC) and muscle stiffness], and plantarflexors maximun force-generating capacity variables (maximum voluntary contraction, maximum muscle activation, rate of torque development, electromechanical delay) were calculated Pre, at the 6th (Wk6), and the 12th week (Wk12) of the protocol in both groups. Results Compared to Pre, STR ROM increased (P < 0.05) at Wk6 (8%) and Wk12 (23%). PRTmax increased at Wk12 (30%, P < 0.05), while MTC stiffness decreased (16%, P < 0.05). Muscle stiffness decreased (P < 0.05) at Wk6 (11%) and Wk12 (16%). No changes in triceps surae architecture and plantarflexors maximum force-generating capacity variables were found in STR (P > 0.05). Percentage changes in ROM correlated with percentage changes in PRTmax (ρ = 0.62, P = 0.01) and MTC stiffness (ρ = − 0.78, P = 0.001). In CTRL, no changes (P > 0.05) occurred in any variables at any time point. Conclusion The expected long-term PST-induced changes in ROM were associated with modifications in the whole passive mechanical properties of the ankle joint, while maximum force-generating capacity characteristics were preserved. 12 weeks of PST do not seem a sufficient stimulus to induce triceps surae architectural changes.

scholarly journals Assessment of the influence of lung inflation state on the quantitative parameters derived from hyperpolarized gas lung ventilation MRI in healthy volunteers

2019 ◽  
Vol 126 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Paul J. C. Hughes ◽  
Laurie Smith ◽  
Ho-Fung Chan ◽  
Bilal A. Tahir ◽  
Graham Norquay ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Lung Volume ◽  
Lung Ventilation ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Longitudinal Measurements ◽  
Anatomical Images ◽  
Lower Lung ◽  
Ventilation Heterogeneity ◽  
Residual Capacity

In this study, the effect of lung volume on quantitative measures of lung ventilation was investigated using MRI with hyperpolarized 3He and 129Xe. Six volunteers were imaged with hyperpolarized 3He at five different lung volumes [residual volume (RV), RV + 1 liter (1L), functional residual capacity (FRC), FRC + 1L, and total lung capacity (TLC)], and three were also imaged with hyperpolarized 129Xe. Imaging at each of the lung volumes was repeated twice on the same day with corresponding 1H lung anatomical images. Percent lung ventilated volume (%VV) and variation of signal intensity [heterogeneity score (Hscore)] were evaluated. Increased ventilation heterogeneity, quantified by reduced %VV and increased Hscore, was observed at lower lung volumes with the least ventilation heterogeneity observed at TLC. For 3He MRI data, the coefficient of variation of %VV was <1.5% and <5.5% for Hscore at all lung volumes, while for 129Xe data the values were 4 and 10%, respectively. Generally, %VV generated from 129Xe images was lower than that seen from 3He images. The good repeatability of 3He %VV found here supports prior publications showing that percent lung-ventilated volume is a robust method for assessing global lung ventilation. The greater ventilation heterogeneity observed at lower lung volumes indicates that there may be partial airway closure in healthy lungs and that lung volume should be carefully considered for reliable longitudinal measurements of %VV and Hscore. The results suggest that imaging patients at different lung volumes may help to elucidate obstructive disease pathophysiology and progression. NEW & NOTEWORTHY We present repeatability data of quantitative metrics of lung function derived from hyperpolarized helium-3, xenon-129, and proton anatomical images acquired at five lung volumes in volunteers. Increased regional ventilation heterogeneity at lower lung inflation levels was observed in the lungs of healthy volunteers.

Endotoxin administration alters the force vs. pCa relationship of skeletal muscle fibers

2000 ◽  
Vol 278 (4) ◽  
pp. R891-R896 ◽  
Author(s):  
G. Supinski ◽  
D. Nethery ◽  
T. M. Nosek ◽  
L. A. Callahan ◽  
D. Stofan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Force ◽  
Fiber Type ◽  
Contractile Proteins ◽  
Hill Coefficient ◽  
Control Group ◽  
Fiber Types ◽  
Endotoxin Administration ◽  
Generating Capacity ◽  
The Hill

Recent work indicates that endotoxemia elicits severe reductions in skeletal muscle force-generating capacity. The subcellular alterations responsible for these decrements have not, however, been fully characterized. One possibility is that the contractile proteins per se are altered in endotoxemia and another is that the mechanism by which these proteins are activated is affected. The purpose of the present study was to assess the effects of endotoxin administration on the contractile proteins by examining the maximum calcium-activated force (Fmax) and calcium sensitivity of single Triton-skinned fibers of diaphragm, soleus, and extensor digitorum longus (EDL) muscles taken from control and endotoxin-treated (8 mg/kg) rats. Fibers were mounted on a force transducer and sequentially activated by serial immersion in solutions of increasing Ca2+ concentration (i.e., pCa 6.0 to pCa 5.0); force vs. pCa data were fit to the Hill equation. All fibers were typed at the conclusion of studies using gel electrophoresis. Fmax, the calcium concentration required for half-maximal activation (Ca50), and the Hill coefficient were compared as a function of muscle and fiber type for the control and endotoxin-treated animals. Control group Fmax was similar for diaphragm, soleus, and EDL fibers, i.e., 112.34 ± 2.64, 111.55 ± 3.66, and 104.05 ± 4.33 kPa, respectively. Endotoxin administration reduced the average Fmax for fibers from all three muscles to 80.25 ± 2.30, 72.47 ± 2.97, and 78.32 ± 2.43 kPa, respectively ( P < 0.001 for comparison of each to control). All fiber types in diaphragm, soleus, and EDL muscles manifested similar endotoxin-related reductions in Fmax. The Ca50 and the Hill coefficient for all fiber types and all muscles were unaffected by endotoxin administration. We speculate that these alterations in the intrinsic properties of the contractile proteins represent a major mechanism by which endotoxemia reduces muscle force-generating capacity.

Effects of body position change on thoracoabdominal motion

1978 ◽  
Vol 45 (4) ◽  
pp. 581-589 ◽  
Author(s):  
V. P. Vellody ◽  
M. Nassery ◽  
W. S. Druz ◽  
J. T. Sharp
Keyword(s):  
Supine Position ◽  
Muscle Force ◽  
Body Position ◽  
Tidal Breathing ◽  
Position Change ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Residual Capacity ◽  
Lateral Decubitus ◽  
Local Compliance

With a linearized respiratory magnetometer, measurements of anteroposterior and lateral diameters of both the rib cage and the abdomen were made at functional residual capacity and continuously during tidal breathing. Twenty-five subjects with normal respiratory systems were studied in the sitting, supine, lateral decubitus, and prone body positions. When subjects changed from sitting to supine position anteroposterior diameters of both rib cage and abdomen decreased while their lateral diameters increased. Both anteroposterior and lateral tidal excursions of the rib cage decreased; those of the abdomen increased. When subjects turned from supine to lateral decubitus position both anteroposterior diameters increased and the lateral diameters decreased. This was associated with an increase in both lateral excursions and a decrease in the abdominal anteroposterior excursions. Diameters and tidal excursions in the prone position resembled those in the supine position. Diameter changes could be explained by gravitational effects. Differences in tidal excursions accompanying body position change were probably related to 1) differences in the distribution of respiratory muscle force, 2) differences in the activity or mechanical advantage of various inspiratory muscles, and 3) local compliance changes in parts of the rib cage and abdomen.

A model for the relation between respiratory neural and mechanical outputs. II. Methods

1981 ◽  
Vol 51 (4) ◽  
pp. 979-989 ◽  
Author(s):  
W. Riddle ◽  
M. Younes
Keyword(s):  
Theoretical Analysis ◽  
Respiratory System ◽  
Spontaneous Breathing ◽  
Muscle Activation ◽  
Indirect Evidence ◽  
Present Communication ◽  
Inspiratory Muscles ◽  
Flow Profiles ◽  
Preceding Communication ◽  
Pressure Output

In the preceding communication we developed a model for the conversion of neural output to mechanical output. We were left with two qualitative uncertainties, namely, the relation between neural output and isometric pressure, and the behavior of inspiratory muscles during expiratory flow; and two quantitative uncertainties concerning the effect of configurational pathway on pressure output, and the slope of the pressure-flow relation. For each of the above uncertainties we made certain assumptions based on indirect evidence but defined reasonable error limits. In the present communication we describe the method of implementing the model and evaluate the significance, in terms of spirometric output, of possible errors in the assumptions. Volume and flow profiles were generated from different neural output profiles. Analysis was repeated when the different assumptions were systematically altered within the limits set by the previous theoretical analysis. We conclude that the pattern of inspiratory muscle activation during spontaneous breathing and the existence of several mechanical interactions within the respiratory system combine to render spirometric output fairly insensitive to most potential errors in our assumptions.

High lung volume increases stress failure in pulmonary capillaries

1992 ◽  
Vol 73 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Z. Fu ◽  
M. L. Costello ◽  
K. Tsukimoto ◽  
R. Prediletto ◽  
A. R. Elliott ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Lung Volume ◽  
Autologous Blood ◽  
Physiological Mechanism ◽  
Transpulmonary Pressure ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Pulmonary Capillaries ◽  
Scanning Electron

We previously showed that when pulmonary capillaries in anesthetized rabbits are exposed to a transmural pressure (Ptm) of approximately 40 mmHg, stress failure of the walls occurs with disruption of the capillary endothelium, alveolar epithelium, or sometimes all layers. The present study was designed to test whether stress failure occurred more frequently at high than at low lung volumes for the same Ptm. Lungs of anesthetized rabbits were inflated to a transpulmonary pressure of 20 cmH2O, perfused with autologous blood at 32.5 or 2.5 cmH2O Ptm, and fixed by intravascular perfusion. Samples were examined by both transmission and scanning electron microscopy. The results were compared with those of a previous study in which the lung was inflated to a transpulmonary pressure of 5 cmH2O. There was a large increase in the frequency of stress failure of the capillary walls at the higher lung volume. For example, at 32.5 cmH2O Ptm, the number of endothelial breaks per millimeter cell lining was 7.1 +/- 2.2 at the high lung volume compared with 0.7 +/- 0.4 at the low lung volume. The corresponding values for epithelium were 8.5 +/- 1.6 and 0.9 +/- 0.6. Both differences were significant (P less than 0.05). At 52.5 cmH2O Ptm, the results for endothelium were 20.7 +/- 7.6 (high volume) and 7.1 +/- 2.1 (low volume), and the corresponding results for epithelium were 32.8 +/- 11.9 and 11.4 +/- 3.7. At 32.5 cmH2O Ptm, the thickness of the blood-gas barrier was greater at the higher lung volume, consistent with the development of more interstitial edema. Ballooning of the epithelium caused by accumulation of edema fluid between the epithelial cell and its basement membrane was seen at 32.5 and 52.5 cmH2O Ptm. At high lung volume, the breaks tended to be narrower and fewer were oriented perpendicular to the axis of the pulmonary capillaries than at low lung volumes. Transmission and scanning electron microscopy measurements agreed well. Our findings provide a physiological mechanism for other studies showing increased capillary permeability at high states of lung inflation.

scholarly journals Nature of the coupling between neural drive and force-generating capacity in the human quadriceps muscle

2015 ◽  
Vol 282 (1819) ◽  
pp. 20151908 ◽  
Author(s):  
François Hug ◽  
Clément Goupille ◽  
Daniel Baum ◽  
Brent J. Raiteri ◽  
Paul W. Hodges ◽  
...  
Keyword(s):  
Muscle Force ◽  
Vastus Lateralis ◽  
Quadriceps Muscle ◽  
Myoelectric Activity ◽  
Neural Drive ◽  
Fascicle Length ◽  
Cross Sectional ◽  
Muscle Fascicle ◽  
Generating Capacity ◽  
The Relationship

The force produced by a muscle depends on both the neural drive it receives and several biomechanical factors. When multiple muscles act on a single joint, the nature of the relationship between the neural drive and force-generating capacity of the synergistic muscles is largely unknown. This study aimed to determine the relationship between the ratio of neural drive and the ratio of muscle force-generating capacity between two synergist muscles (vastus lateralis (VL) and vastus medialis (VM)) in humans. Twenty-one participants performed isometric knee extensions at 20 and 50% of maximal voluntary contractions (MVC). Myoelectric activity (surface electromyography (EMG)) provided an index of neural drive. Physiological cross-sectional area (PCSA) was estimated from measurements of muscle volume (magnetic resonance imaging) and muscle fascicle length (three-dimensional ultrasound imaging) to represent the muscles' force-generating capacities. Neither PCSA nor neural drive was balanced between VL and VM. There was a large ( r = 0.68) and moderate ( r = 0.43) correlation between the ratio of VL/VM EMG amplitude and the ratio of VL/VM PCSA at 20 and 50% of MVC, respectively. This study provides evidence that neural drive is biased by muscle force-generating capacity, the greater the force-generating capacity of VL compared with VM, the stronger bias of drive to the VL.

Characteristics of the defocused spherical Fabry-Pérot interferometer as a quasi-linear dispersion instrument for high resolution spectroscopy of pulsed laser sources

1968 ◽  
Vol 263 (1140) ◽  
pp. 209-223 ◽  
Keyword(s):  
Laser Beam ◽  
Optical Design ◽  
Pulsed Laser ◽  
Resolving Power ◽  
High Resolution Spectroscopy ◽  
Radius Of Curvature ◽  
Spherical Mirror ◽  
Linear Dispersion ◽  
Fabry Perot ◽  
Very High

Defocused spherical mirror Fabry—Pérot etalons, in which the mirror separation is slightly less than the common radius of curvature, produce a multiple-beam fringe pattern of concentric rings, with quasi-linear spectral dispersion over an appreciable annular region corresponding to two free spectral ranges. The characteristics of these interferograms are discussed in relation to their many advantages for pulsed laser spectroscopy. These advantages include: (i) accuracy of frequency difference measurement; (ii) high illumination of the detector with moderate energy density in the laser beam; (iii) ease of alinement and permanent adjustment of the mirrors leading to the attainment in practice of a very high instrumental finesse (N R values of up to 90 have been achieved); (iv) measurement of degree of spatial coherence of laser beam; (v) ease of matching the interferogram to the spatial resolution of the detector. A simple optical path relation determines the positions of the fringes and the location of the quasilinear dispersion region. The interfering wavefronts, formed by multiple reflexion, have been numerically computed and summed to provide information on the finesse, fringe profiles, contrast and optimum conditions of use of this new, very high resolving power (107 to 108) quasi-linear spectrographic disperser. Constructional details are described and optical design criteria are discussed, together with the various experimental arrangements for employing the instrument. Comparison is made with the equivalent confocal and plane Fabry—Pérot etalons and methods of simultaneously measuring

The Rate of Isometric Inspiratory Pressure Development as a Measure of Responsiveness to Carbon Dioxide in Man

1975 ◽  
Vol 49 (1) ◽  
pp. 57-68 ◽  
Author(s):  
A. W. Matthews ◽  
J. B. L. Howell
Keyword(s):  
Initial Rate ◽  
Ventilatory Response ◽  
Pressure Change ◽  
Normal Subjects ◽  
Inspiratory Pressure ◽  
Pulmonary Mechanics ◽  
Inspiratory Muscles ◽  
Pressure Development ◽  
Respiratory Centre ◽  
Very High

1. A technique has been developed for assessing CO2 responsiveness by measuring the maximum rate of isometric inspiratory pressure change at the mouth [(dP/dt)max.]. 2. By use of a rebreathing technique, the (dP/dt)max. response to CO2 was shown to correlate well with the ventilatory response in thirty-two normal subjects. 3. The addition of an external flow resistance sufficient to reduce the ventilatory response by a mean of 33.4% produced no significant mean change in the (dP/dt)max. response in thirty subjects. 4. In six patients recovering from bronchial asthma, reduction of airways obstruction led to a mean increase in the ventilatory response of 109% without any significant mean change in the (dP/dt)max. response. 5. An increase in lung volume did not reduce the (dP/dt)max. response in five normal subjects. 6. At very high lung volumes, six normal subjects were able to develop a higher (dP/dt)max. during voluntary inspiratory efforts than has been recorded during spontaneous breathing response to CO2. 7. It is believed that (dP/dt)max. represents the initial rate of development of force by the inspiratory muscles before this can be modified by mechanical loading, proprioceptive feedback mechanisms or conscious response and can therefore be used to study changes in the motor output of the respiratory centre in response to ventilatory stimuli independently of pulmonary mechanics.

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