01/02/2026
💨 𝗧𝗵𝗲 𝗗𝗶𝗮𝗽𝗵𝗿𝗮𝗴𝗺: 𝗠𝗼𝗿𝗲 𝗧𝗵𝗮𝗻 𝗮 𝗕𝗿𝗲𝗮𝘁𝗵𝗶𝗻𝗴 𝗠𝘂𝘀𝗰𝗹𝗲
From an Equine osteopathic perspective, the diaphragm is one of the most influential structures in the horse’s entire body, yet it’s still commonly thought of as “just” a breathing muscle.
𝘠𝘦𝘴, 𝘪𝘵 𝘱𝘭𝘢𝘺𝘴 𝘢 𝘤𝘦𝘯𝘵𝘳𝘢𝘭 𝘳𝘰𝘭𝘦 𝘪𝘯 𝘳𝘦𝘴𝘱𝘪𝘳𝘢𝘵𝘪𝘰𝘯.
But more accurately, the diaphragm is a pressure regulator, a mechanical integrator, and a meeting point between structure, organs and the nervous system.
𝗪𝗵𝗮𝘁 𝘁𝗵𝗲 𝗱𝗶𝗮𝗽𝗵𝗿𝗮𝗴𝗺 𝗮𝗰𝘁𝘂𝗮𝗹𝗹𝘆 𝗶𝘀:
The diaphragm is a large, dome-shaped musculotendinous structure separating the thoracic (chest) cavity from the abdominal cavity.
It is not a flat sheet > it is a dynamic, three-dimensional structure designed to move, adapt and transmit force.
𝗔𝗻𝗮𝘁𝗼𝗺𝗶𝗰𝗮𝗹𝗹𝘆, 𝘁𝗵𝗲 𝗱𝗶𝗮𝗽𝗵𝗿𝗮𝗴𝗺 𝗮𝗻𝗰𝗵𝗼𝗿𝘀 𝗶𝗻𝘁𝗼 𝗸𝗲𝘆 𝘀𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗮𝗹 𝗿𝗲𝗴𝗶𝗼𝗻𝘀:
♦️The Sternum (Sternal Fibres): The ventral part of the diaphragm attaches to the xiphoid process (the rear part of the breastbone).
♦️The costae (ribs)often listed around ribs 9–18, depending on the source
♦️The lumbar spine (crural attachments)
At its centre lies the central tendon, a strong tendinous region that acts as a hub for pressure transmission and mechanical continuity.
From this centre, the diaphragm forms two domes, left and right, which attach caudally into the lumbar spine via the crura:
➡️The right dome and right crux are stronger and extend further caudally into the lumbar region
➡️The left dome and left crux are shorter and less robust
This asymmetry is normal, but it has important implications for spinal mechanics, visceral tension and movement patterns.
(These implications will be explored in later parts of this series.)
‼️𝗪𝗵𝗮𝘁 𝗺𝗮𝘁𝘁𝗲𝗿𝘀 𝗵𝗲𝗿𝗲 𝗶𝘀 𝘁𝗵𝗶𝘀:
The diaphragm is structurally integrated into the ribs, sternum and lumbar spine, it cannot move well if those structures cannot move well.
𝘏𝘰𝘸 𝘪𝘵 𝘴𝘩𝘰𝘶𝘭𝘥 𝘮𝘰𝘷𝘦:
During the process of both inspiration and expiration, the diaphragm should move rhythmically:
Caudally and ventrally (backwards and downwards) on inspiration
Cranially (forwards towards the head) on expiration
When the diaphragm contracts, it flattens and moves caudally.
This caudal–ventral movement creates expansion in three dimensions:
Vertical: the dome descends
Transverse: the ribs widen and elevate
Sagittal: the sternum lifts
𝗔𝘀 𝗮 𝗿𝗲𝘀𝘂𝗹𝘁:
Pressure within the chest cavity drops, drawing air into the lungs
The abdominal contents are gently compressed and then released
Pressure is redistributed rather than trapped
During expiration, the diaphragm returns cranially with a smaller amplitude, relying on rib mobility and abdominal compliance to regulate airflow and pressure efficiently.
Crucially, as the ribs move ventrally at the costovertebral joints, the spine is passively guided into extension, allowing the vertebral column to follow the respiratory motion while maintaining integrity of the spinal canal.
Straight away, we can see why rib mobility, sternum alignment and thoracolumbar freedom are so important for something as seemingly simple as breathing. Here we can think of why thoracic adjustments without rib n diaphragm & visceral assessment may not bring real long term alignment!
Why this matters beyond breathing
Because the diaphragm attaches to the ribs, sternum and lumbar spine, and blends into fascial continuities with the liver, stomach, spleen and kidneys, its movement affects far more than respiration.
When diaphragmatic motion is free and elastic:
✴️The ribs, spine and viscera move as a coordinated unit
✴️Blood and lymphatic flow are supported
✴️Pressure is managed efficiently throughout the body
In faster gaits such as canter and gallop, this becomes even more relevant.
At that point, breathing and locomotion are mechanically linked ↙️ the diaphragm becomes the primary driver of respiration, working in rhythm with spinal motion and abdominal mass.
If it cannot move well, the horse must compensate elsewhere.
𝗛𝗼𝘄 𝗿𝗲𝘀𝘁𝗿𝗶𝗰𝘁𝗶𝗼𝗻 𝗰𝗮𝗻 𝘀𝗵𝗼𝘄 𝘂𝗽:
When diaphragmatic movement is restricted; whether by rib stiffness, fascial tension, visceral load or neurological irritation, the effects are rarely local.
This is why diaphragm restriction may present as:
°Reduced performance or stamina
°Rib or thoracolumbar stiffness
°Apparent loss of core stability
°Hindquarter or “terrain-related” issues
°Horses that look barrel-shaped or bloated > then visibly change after treatment
Many owners are surprised when a horse looks physically slimmer or lighter post-treatment.
That isn’t weight loss, it’s pressure redistribution.
🧠 𝗧𝗵𝗶𝘀 𝗶𝘀 𝗣𝗮𝗿𝘁 𝟭 𝗼𝗳 𝗮 𝘄𝗲𝗲𝗸𝗲𝗻𝗱 𝘀𝗲𝗿𝗶𝗲𝘀 𝗲𝘅𝗽𝗹𝗼𝗿𝗶𝗻𝗴 𝘁𝗵𝗲 𝗱𝗶𝗮𝗽𝗵𝗿𝗮𝗴𝗺 𝗳𝗿𝗼𝗺 𝗺𝘆 𝘃𝗶𝗲𝘄𝗽𝗼𝗶𝗻𝘁.
Over the coming parts, I’ll begin to unpack:
Its anatomical relationships in more depth
Why ribs and sternum matter so much
How pressure, posture and organs influence one another
And why diaphragm work is never just about breathing.
Some parts will be subscriber-only, where I’ll go deeper into clinical thinking, assessment priorities and real-world patterns I see repeatedly in practice.
📩 For professionals: this topic alone forms multiple days of CPD content coming in March.. There is far more to this than can ever fit into a social media post.
👉 Part 2 next weekend: the anatomy and pressure story behind the diaphragm.
