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    The respiratory muscles during exercise

    Although during exercise respiratory muscles are finely controlled, they can contribute to limit performance

    Breathe (Sheff). 2016 Jun; 12(2): 165–168.

    doi: 10.1183/20734735.008116

    PMCID: PMC4933622 PMID: 27408635

    The respiratory muscles during exercise

    Andrea Aliverti

    Author information Copyright and License information Disclaimer

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    Short abstract

    Although during exercise respiratory muscles are finely controlled, they can contribute to limit performance http://ow.ly/qYUc300m9uP

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    How is the “ventilatory pump” made?

    From a functional point of view, there are three groups of respiratory muscles: the diaphragm, the rib cage muscles and the abdominal muscles. Each group acts on the chest wall and its compartments, i.e. the lung-apposed rib cage, the diaphragm-­apposed rib cage and the abdomen. Contraction of the diaphragm expands the abdomen and the lower part of the rib cage (abdominal rib cage). The rib cage muscles, including the intercostals, the parasternals, the scalene and the neck muscles, mostly act on the upper part of the rib cage (pulmonary rib cage) and are both inspiratory and expiratory. The abdominal muscles act on the abdomen and the abdominal rib cage and are expiratory. When each muscle group contracts alone or the contraction is predominant compared to the other groups, undesirable effects (such as “paradoxical” inward or outward motion during inspiration and expiration, respectively) occur on at least one of the compartments. A highly coordinated recruitment of two or three muscle groups is required to avoid these effects. During breathing at rest, this is accomplished by the coordinated activity of the diaphragm and inspiratory rib cage muscles. Normally no expiratory muscles are used [1].

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    How does the ventilatory pump work during exercise?

    During exercise the increased ventilatory demands determine an increased neural drive to the respira­tory muscles. This determines an increased mechanical power developed by the muscles. Muscle power is equal to velocity of shortening multiplied by pressure.

    Differently than rest, during exercise the diaphragm is primarily a “flow generator”. This means that its mechanical power is mainly expressed as velocity of shortening rather than pressure. Conversely, rib cage and abdominal muscles are primarily “pressure generators”, i.e. develop the pressures required to move the rib cage and abdomen, respectively [1].

    Differently than rest, during exercise the expira­tory muscles play an active role in breathing. Within each single breath their action is highly coordinated with that of the inspiratory rib cage muscles. During inspiration, while the rib cage muscles contract, the abdominal muscles gradually relax, and vice versa during expiration. This mechanism has several effects: 1) it prevents rib cage distortion; 2) the diaphragm is unloaded and can act as a flow generator; and 3) the volume of the abdomen is decreased below resting levels [1, 2]. As a result, end-expiratory lung volume is decreased during exercise (figure 1) and the mechanics of breathing is optimised for several reasons. Tidal volume occurs in the most compliant part of the respiratory system; the diaphragm is lengthened and thus works near its optimal length; at each breath part of the required inspiratory work is previously stored in the form of elastic energy during the previous expiration [3].

    FIGURE 1

    The main features of respiratory muscle action during exercise. TLC: total lung capacity; EILV: end-inspiratory lung volume; EELV: end-expiratory lung volume; RV: residual volume.

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    How do respiratory muscles undertake the increased ventilatory demands of exercise?

    At moderate levels of exercise, metabolic requirements increase in parallel with alveolar ventilation, arterial blood–gas tensions and acid-base balance are maintained close to their levels at rest. The mechanics of the breathing pattern is regulated so precisely that the work performed by the respiratory muscles is minimised.

    At higher levels of exercise up to maximal exercise, the pressures produced by the respiratory muscles are well below their maximum. At maximal exercise, the oxygen consumed by the respiratory muscles to breathe is only ∼10% of the total [4]. However, this is only true for healthy subjects not those who are trained athletes. In fact, in highly fit endurance athletes the pressure produced by inspiratory muscles can approach the maximum and expiratory pressures are increased to levels at which dynamic compression of the airways determines expiratory flow limitation [5]. This phenomenon also frequently occurs in elderly subjects due to the age-related loss of lung elastic recoil [6], and is a common feature of patients with chronic obstructive pulmonary disease, not only during exercise but also at rest in the most severe cases. When expiratory flow is limited, end-expiratory lung volume has to be increased to allow for further increases of flow. In other words, expiratory flow limitation causes the so called “dynamic hyperinflation”. At high operational lung volumes, the inspiratory muscles have to overcome a higher elastic load offered by the lung and chest wall [7]. Moreover, they are shorter and, therefore, less capable of generating pressure. As a result, in these conditions the oxygen consumed by the respiratory muscles is increased [4, 8].

    स्रोत : www.ncbi.nlm.nih.gov

    Muscles of Respiration

    Original Editors - Rachael Lowe

    Muscles of Respiration

    Online Course: Respiratory Management Following a Spinal Cord Injury

    Introduction

    The muscles of respiration are also called the 'breathing pump muscles', they form a complex arrangement in the form of semi-rigid bellows around the lungs.

    All muscles that are attached to the human rib cage have the inherent potential to cause a breathing action.

    Muscles that helpful in expanding the thoracic cavity are called the inspiratory muscles because they help in inhalation.

    Those that compress the thoracic cavity are called expiratory muscles and they induce exhalation.

    These muscles possess exactly the same basic structure as all other skeletal muscles, and they work in concert to expand or compress the thoracic cavity.[1]

    The speciality of these muscles are that they are composed of fatigue resistant muscle fibers, they are controlled by both voluntary and involuntary mechanisms (if we want to take a breath we can, even if we do not think about breathing the body automatically does it)[2]

    Image: Overview of the respiratory system[3]

    [4] [5]

    Primary Muscles

    The primary inspiratory muscles are the diaphragm and external intercostals. Relaxed normal expiration is a passive process, happens because of the elastic recoil of the lungs and surface tension. However there are a few muscles that help in forceful expiration and include the internal intercostals, intercostalis intimi, subcostals and the abdominal muscles.[6]

    The muscles of inspiration elevate the ribs and sternum, and the muscles of expiration depress them.[7].

    Accessory Muscles

    The accessory inspiratory muscles are the sternocleidomastoid, the scalenus anterior, medius, and posterior, the pectoralis major and minor, the inferior fibres of serratus anterior and latissimus dorsi, the serratus posterior superior may help in inspiration also the iliocostalis cervicis[7]. Technically any muscle attached to the upper limb and the thoracic cage can act as an accessory muscle of inspiration through reverse muscle action (muscle work from distal to proximal)[2]

    The accessory expiratory muscles are the abdominal muscles: rectus abdominis, external oblique, internal oblique, and transversus abdominis.

    And in the thoracolumbar region the lowest fibres of iliocostalis and longissimus, the serratus posterior inferior and quadratus lumborum. The accessory muscles are recruited during times of exercising because of the increased metabolic need and also during dysfunction in the respiratory system[6]

    Diaphragm

    It's a double-domed musculotendinous sheet of internal skeletal muscle located at the inferior-most aspect of the rib cage that separates the thoracic cavity from the abdominal cavity.

    It serves two main functions:

    [8]

    Diaphragm(inferior view)

    Origin: Xiphoid process (posterior surface), lower six ribs and their costal cartilage (inner surface) and upper three lumbar vertebrae as right crus and upper two lumbar vertebrae as left crus.

    Insertion: central tendon

    Nerve Supply: Motor nerve supply by Phrenic nerve (C3 C4 C5) and sensory supply by phrenic nerve to central tendon and lower 6 or 7 intercostal nerve to peripheral parts.[8]

    Blood supply: inferior phrenic arteries deliver the majority of blood supply and the remaining supply is delivered via superior phrenic, musculophrenic and pericardiacophrenic arteries.

    Action: diaphragm is the main inspiratory muscle, during inspiration it contracts and moves in an inferior direction that increases the vertical diameter of the thoracic cavity and produces lung expansion, in turn, the air is drawn in.[9]

    Intercostal muscles

    They are three types: External intercostal muscles (the most superficial muscle of intercostal muscles), internal intercostal muscles, and innermost intercostal muscles.

    External intercostal muscles

    Origin: inferior border of rib above and

    Insertion: superior border of rib below

    Internal intercostal muscles

    Origin: from the costal groove (lower part of inner surface of rib near the inferior border) of the rib above and

    स्रोत : www.physio-pedia.com

    Muscles of respiration

    Muscles of respiration

    From Wikipedia, the free encyclopedia

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    Muscles of respiration

    Muscles of the body’s respiration

    Identifiers MeSH D012132

    Anatomical terminology

    [edit on Wikidata]

    The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during quiet breathing. The elasticity of these muscles is crucial to the health of the respiratory system and to maximize its functional capabilities.

    Contents

    1 Diaphragm 2 Accessory muscles

    3 Muscles of exhalation

    4 References 5 Further reading

    Diaphragm[edit]

    Main article: Thoracic diaphragm

    The diaphragm is the major muscle responsible for breathing. It is a thin, dome-shaped muscle that separates the abdominal cavity from the thoracic cavity. During inhalation, the diaphragm contracts so that its center moves caudally (downward) and its edges move cranially (upward). This compresses the abdominal cavity, raises the ribs upward and outward and thus expands the thoracic cavity. This expansion draws air into the lungs. When the diaphragm relaxes, elastic recoil of the lungs causes the thoracic cavity to contract, forcing air out of the lungs, and returning to its dome-shape.[1] The diaphragm is also involved in non-respiratory functions, helping to expel vomit, faeces, and urine from the body by increasing intra-abdominal pressure, and preventing acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus.

    Accessory muscles[edit]

    Along with the diaphragm, the intercostal muscles are one of the most important groups of respiratory muscles. These muscles are attached between the ribs and are important in manipulating the width of the rib cage. There are three layers of intercostal muscles. The external intercostal muscles are most important in respiration. These have fibres that are angled obliquely downward and forward from rib to rib.[2] The contraction of these fibres raises each rib toward the rib above, with the overall effect of raising the rib cage, assisting in inhalation.

    Accessory muscles of respiration are muscles that assist, but do not play a primary role, in breathing. Use of these while at rest is often interpreted as a sign of respiratory distress.[3] There is no definitive list of accessory muscles, but the sternocleidomastoid and the scalenes (anterior, middle, and posterior) are typically included, as they assist in elevating the rib cage.[4] The involvement of these muscles seems to depend on the degree of respiratory effort. During quiet breathing, the scalenes are consistently physically active, while the sternocleidomastoids are quiet.[5] With an increase in the respiratory volume, sternocleidomastoids also become active.[6] Both muscles are simultaneously activated when one breathes in at the maximal flow rate.[5]

    Apart from the above neck muscles, the following muscles have also been observed contributing to respiration: serratus anterior, pectoralis major and pectoralis minor, trapezius, latissimus dorsi, erector spinae, iliocostalis, quadratus lumborum, serratus posterior superior, serratus posterior inferior, levatores costarum, transversus thoracis, subclavius (Kendall et al., 2005). The levator labii superioris alaeque nasi muscle lifts the sides of the nostrils.

    Muscles of exhalation[edit]

    During quiet breathing, there is little or no muscle contraction involved in exhalation; this process is simply driven by the elastic recoil of the lungs. When forceful exhalation is required, or when the elasticity of the lungs is reduced (as in emphysema), active exhalation can be achieved by contraction of the abdominal wall muscles (rectus abdominis, transverse abdominis, external oblique muscle and internal oblique muscle). These press the abdominal organs cranially (upward) into the diaphragm, reducing the volume of the thoracic cavity.[1]

    The internal intercostal muscles have fibres that are angled obliquely downward and backward from rib to rib.[2] These muscles can therefore assist in lowering the rib cage, adding force to exhalation.[1]

    References[edit]

    ^ Jump up to:

    Ratnovsky, Anat (2008). "Mechanics of respiratory muscles". . 163 (1–3): 82–89. doi:10.1016/j.resp.2008.04.019. PMID 18583200. S2CID 207505401.

    ^ Jump up to:

    Kim E. Barrett; Susan M. Barman; Scott Boitano; Heddwen Brooks (24 July 2009). "35. Pulmonary Function". . McGraw-Hill Companies,Incorporated. ISBN 978-0-07-160567-0.

    Further reading[edit]

    Kendall, F., McCreary, E., Provance, P., Rodgers, M., Romai, W. (2005). Muscles testing and function with posture and pain (5th ed.). PA, USA: Lippincott Williams & Wilkins.

    Authority control: National libraries

    GermanyIsraelUnited StatesCzech Republic

    Categories: Respiration

    स्रोत : en.wikipedia.org

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