28/10/2025
🐎 Scapulohumeral and Humeroradioulnar Rhythms in the Horse
The Scapulohumeral Rhythm
The scapulohumeral rhythm describes the coordinated motion between the scapula and the humerus during protraction and retraction of the forelimb.
Because the horse’s scapula is not attached to the skeleton by a bony joint but instead suspended within the thoracic sling of muscles and fascia, this rhythm depends entirely on myofascial coordination and neuromuscular timing.
As the limb moves forward:
• The scapula glides and rotates cranially and dorsally along the thoracic wall.
• The humerus flexes at the scapulohumeral (shoulder) joint, swinging forward.
During retraction:
• The scapula rotates caudally,
• The humerus extends, aligning to bear weight and transfer load through the sling.
This continuous interplay allows the shoulder to function as a shock-absorbing, energy-conserving unit, distributing motion and tension smoothly between the scapular and humeral segments.
A well-tuned scapulohumeral rhythm keeps the forehand light, lengthens the stride, and maintains balance through the thoracic region.
The Humeroradioulnar Rhythm
The humeroradioulnar rhythm is the coordinated movement between the humerus, radius, and ulna as the limb flexes and extends in stride.
• During protraction, as the scapula and humerus swing forward, the elbow flexes, helping lift the forelimb and clear the ground.
• As the limb retracts into stance, the elbow extends, allowing the radius and ulna to align with the humerus and efficiently transmit ground forces upward through the limb.
This rhythm ensures that movement initiated at the scapula and shoulder is carried seamlessly down the limb, maintaining stride integrity, shock absorption, and timing between upper and lower segments.
Integration Through the Thoracic Sling
Both rhythms rely on the stability and elasticity of the thoracic sling—the muscular and fascial network that suspends the trunk between the forelimbs.
When the sling is strong and responsive:
• The scapula glides freely against the ribcage.
• The humerus moves smoothly within its joint.
• The elbow maintains synchronized timing with the rest of the limb.
Loss of tone or asymmetry within the sling disrupts this chain, leading to:
• Reduced shoulder freedom
• Shortened stride
• Compensatory tension in the neck, pectoral region, or back
Restoring Healthy Rhythm
Reestablishing these rhythmic relationships depends on coordination, proprioceptive clarity, and fascial suppleness, not force or range alone.
• Manual therapies such as massage or myofascial release reduce adhesions and allow the scapula to slide freely over the thorax.
• Targeted movement work—hill work, raised poles, and controlled in-hand exercises—retrain timing between scapular rotation, humeral swing, and elbow extension.
• Balance and confidence within the nervous system are essential; a relaxed, supported horse naturally re-patterns efficient rhythm.
When these systems work together, the result is effortless movement:
the forehand becomes supple, the stride lengthens, and energy flows freely from ground to spine.