View source for The Effect of Posture on the Diaphragm

== Forward Head Posture ==
[[File:Chris-benson-yx-iJFybOBQ-unsplash.jpg|thumb|FHP]]
FHP is "a poor habitual neck posture that is defined by hyperextension of the upper cervical vertebrae and forward translation of the cervical vertebrae".<ref name=":2" />This postural malalignment can also become a compensatory pain relieving adaptation in chronic neck pain, an adaptation to improve lung capacity in obstructive lung condition or in response to postural changes in the thoracic spine. <ref>Ahmad AM, Kamel KM, Mohammed RG. Effect of forward head posture on diaphragmatic excursion in subjects with non-specific chronic neck pain. A case-control study. Physiother Quart. 2020;28(3):9–13</ref>

FHP affects chest expansion and the activity of the [[Muscles of Respiration|respiratory muscles]], which can lead to reduced [[Alveoli|alveolar]] ventilation.<ref name=":1" /><ref>Okuro RT, Morcillo AM, Ribeiro MÂ, Sakano E, Conti PB, Ribeiro JD. [https://www.scielo.br/j/jbpneu/a/tCkpp5ZTsgjpwqvSFmTZfxs/?lang=en Mouth breathing and forward head posture: effects on respiratory biomechanics and exercise capacity in children]. Jornal Brasileiro de Pneumologia. 2011;37:471-9.</ref> Zafar et al.<ref name=":1" /> found that induced FHP in healthy subjects has an immediate impact on respiratory function.  They suggested that this could be caused by a temporary entrapment of the [[Phrenic Nerve|phrenic nerve]] (i.e. the [[Neurone|nerve]], which supplies the diaphragm). This entrapment decreases neural activity and ultimately weakens the diaphragm.<ref name=":1" />

Patients with forward head posture have reduced diaphragmatic excursion. The abdominal muscle shortening and changes in the shape and expansion of the anteroposterior aspect of the lower thorax can explain this. As a result, diaphragm excursion becomes limited. Hodges et al<ref>Hodges PW, Gurfinkel VS, Brumagne S, Smith TC, Cordo PC. [https://link.springer.com/article/10.1007/s00221-002-1040-x Coexistence of stability and mobility in postural control: evidence from postural compensation for respiration.] Experimental brain research. 2002 Jun;144(3):293-302.</ref><ref>Hodges PW, Butler JE, McKenzie DK, Gandevia SC. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1160083/ Contraction of the human diaphragm during rapid postural adjustments]. J Physiol. 1997;505 ( Pt 2)(Pt 2):539-48.</ref> deduced that altered diaphragm function leads to [[Core Muscles|core muscle]] instability, which can result in other systemic and musculoskeletal disorders, including spinal instability.  

A FHP has an impact on respiratory [[biomechanics]].<ref name=":4">Triangto K, Widjanantie SC, Nusdwinuringtyas N. [https://www.researchgate.net/publication/344879018_Biomechanical_Impacts_of_Forward_Head_Posture_on_the_Respiratory_Function Biomechanical Impacts of Forward Head Posture on the Respiratory Function.] Indonesian Journal of Physical Medicine & Rehabilitation. 2019;8(02):50-64.</ref> A prolonged forward head posture can lead to kyphotic posture, reduction in the mobility of ribcage, and modification in function of all respiratory muscular attachments such as sternocleidomastoids, intercostals, and the diaphragm.  It results in an expansion of the upper thorax and a contraction of the lower thorax. Thoracic elevation observed in forward head posture and decreased mobility of the thoracolumbar region is caused by an increased tone in the sternocleidomastoid muscle. <ref>Huggare JA, Laine-Alava MT. Nasorespiratory function and head posture. Am J Orthod Dentofacial Orthop 1997;112(5):507-11.</ref> The biomechanical impacts of forward head posture on respiratory function include development of  restrictive lung disorder <ref name=":4" />, decreased respiratory function<ref name=":2">Koseki T, Kakizaki F, Hayashi S, Nishida N, Itoh M. [https://www.jstage.jst.go.jp/article/jpts/31/1/31_jpts-2018-328/_pdf/-char/ja Effect of forward head posture on thoracic shape and respiratory function.] Journal of Physical Therapy Science. 2019;31(1):63-8.</ref>, and decreasing the primary respiratory parameters: vital capacity (FVC), forced expiratory volume in the 1st second (FEV1), expiratory reserve volume (ERV), inspiratory reserve volume (iRV), and peak expiratory flow (PEF). <ref name=":2" />Additionally, the forward head posture tends to decrease the SNIP values compared to the normal upright sitting, indicating a reduction in the diaphragm strength.<ref name=":1" />

=== Interventions ===
For the diaphragm of patients with an FHP to be more effective during breathing, we need to:<ref name=":3" />

* Restore the normal length-tension relationship
** Postural alignment is necessary for effective respiratory muscle training as trunk rotation posture may limit chest wall movement. Diaphragm asymmetry is consistent with trunk rotation, negatively affecting lung volume. <ref name=":5" />
** Myofascial release of the diaphragm to indirectly stretch the diaphragm muscle fibres for muscle tension reduction, normalising fibre length, and promoting muscle contraction efficiency.<ref>Rocha T, Souza H, Brandão DC, Rattes C, Ribeiro L, Campos SL, Aliverti A, de Andrade AD. [https://www.sciencedirect.com/science/article/pii/S1836955315001009?via%3Dihub The Manual Diaphragm Release Technique improves diaphragmatic mobility, inspiratory capacity and exercise capacity in people with chronic obstructive pulmonary disease: a randomised trial]. J Physiother. 2015 Oct;61(4):182-9. </ref>
The following video demonstrates a self-release technique for the diaphragm:{{#ev: youtube|v=b_xXvW_BOJw|300}}<ref>Stop chasing pain. Diaphragm Muscle Self Release for Tension.  Available from: s://www.youtube.com/watch?v=b_xXvW_BOJw [last accessed 8/11/2023]</ref>

* Improve mobility and expansion in the chest wall
** Increase strength and mobility of the intercostal muscles through chest expansion exercises, rotation movement, swimming and various ball games (use of upper limbs).<ref name=":5">Cao Y, Li P, Wang Y, Liu X, Wu W. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9108326/pdf/fphys-13-872277.pdf Diaphragm Dysfunction and Rehabilitation Strategy in Patients With Chronic Obstructive Pulmonary Disease]. Front Physiol. 2022 May 2;13:872277. </ref>
** Chest mobilisation: The patient sits and bends away from the tight side. Next, the patient inhales to expand that side of the chest. Then, the patient bends toward the tight side during expiration. Repeat multiple times for a total of 6 minutes of exercises.
** The upper chest mobilisation and stretching of the pectoralis muscles: The patient sits in a chair with hands clasped behind the head. The patient horizontally abducts the arms during a deep inspiration followed by bringing the elbows together and bending forward during expiration. Repeat multiple times for a total of 6 minutes of exercises.
** Chest mobilisation and core stabilisation exercises improve forced expiratory volume and vital capacity.<ref>Park SJ, Lee JH, Min KO. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509578/pdf/jpts-29-1144.pdf Comparison of the effects of core stabilization and chest mobilization exercises on lung function and chest wall expansion in stroke patients]. J Phys Ther Sci. 2017 Jul;29(7):1144-1147.</ref>
* Relieve the load on accessory respiratory muscles in the [[Cervical Anatomy|neck]]<ref name=":3">Haghighat F, Moradi R, Rezaie M, Yarahmadi N, Ghaffarnejad F. [https://assets.researchsquare.com/files/rs-53279/v1/4bd8d8b9-3540-4500-a169-66aab3be8027.pdf?c=1631854601 Added Value of Diaphragm Myofascial Release on Forward Head Posture and Chest Expansion in Patients With Neck Pain: A Randomized Controlled Trial.]</ref>
** The accessory inspiratory muscles consist of the sternocleidomastoids (SCM), scalenes, pectoralis major and minor, and inferior fibres of the serratus anterior and latissimus dorsi
** Forward head posture induces muscle imbalances. Levator scapulae, sternocleidomastoid, anterior scalene, posterior cervical extensor, upper trapezius and pectoralis muscles become short or stiff.  The deep cervical neck flexor, rhomboid, and serratus anterior muscles become inhibited or weak. These postural changes lead to overactivity of accessory respiratory muscles.<ref name=":6">Haghighat F, Moradi R, Rezaie M, Yarahmadi N, Ghaffarnejad F. Added Value of Diaphragm Myofascial Release on Forward Head Posture and Chest Expansion in Patients With Neck Pain: A Randomized Controlled Trial. Available from https://assets.researchsquare.com/files/rs-53279/v1/4bd8d8b9-3540-4500-a169-66aab3be8027.pdf?c=1631854601 [last access 8.11.2023]</ref>  
** Weak, overactive, or tight accessory muscles of respiration, especially SCM and anterior scalenus, can increase respiratory inefficiency
** Diaphragm myofascial release combined with an exercise program can improve FHP and chest mobility compared to exercises alone.<ref name=":6" />  

Watch this 6-minute video on how to measure and correct FHP.{{#ev: youtube|9OdAid7vO5w}}