The rein back might seem simple, but it's a crucial exercise for performance horses.
Or is it?
Part 1 of this blog will take a deep dive into the biomechanics of the rein back because how can we work on an exercise if we don’t truly understand it?
What is the rein back?
In my opinion, when done correctly, the rein back is one of the most beneficial exercises for improving your horse’s posture and athletic ability.
“Rein back is a rearward diagonal movement with a two-beat rhythm, without a moment of suspension. Each diagonal pair of legs is raised and returned to the ground alternatively, with the forelegs aligned on the same track as the hind legs.”
It's a highly gymnastic and dynamic exercise as it immediately engages your horse's entire body. When executed properly, this exercise requires your horse to engage and use its hindquarters by shifting weight from the front end to the hindquarters. It might sound easy, but as you'll soon read, the muscles involved in generating this movement are advanced. That explains why many horses struggle with their rein back and engaging their hindquarters.
The biomechanics of the rein back
The primary biomechanical elements of the rein back involve maximal concentric contraction of the iliopsoas on one side, initiating flexion of the LS joint. This action activates the forehand muscles, depending on the diagonal pair. For instance, if the left fore is back, these forehand muscles are lengthened, pulling the neck backward (refer to the image below).
The action of the diagonal pairs during the rein back allows us to assess the fore and hind limbs separately.
Forelimb Biomechanics
There are two principal phases regarding the forelimbs, neck, and head balance system. Protraction of the forelimb, compared to other gaits, occurs during weight bearing, pushing the horse backward (Denoix, 2014). During retraction, the forelimb is non-weight-bearing, leading to ground contact through the point of the toe (see image below).
Protraction of the forelimb 🐾
It begins with the forward swing of the lower scapula, as the rest of the limb extends and stabilizes through isometric contraction of the extensor muscles (see image below). The supraspinatus m extends the scapulohumeral joint, increasing the forelimb's range of motion (ROM).
Scapulohumeral joint angle extension involves a sliding movement. As the hoof is fixed on the ground, limb protraction shifts the body backward. The lower part of the scapula moves forward while the upper part is fixed backward due to the thoracic trapezius and serratus ventralis thoracic m.
Retraction of the forelimb 🏇
This occurs when the limb is non-weight-bearing, suggesting less stress compared to forward gaits. The entire limb's backward swing results from flexion of the Scapulohumeral joints. The overall ROM of the forelimb is determined by retraction and the associated muscle attachments pulling the scapula forward. Muscles involved in this action include the rhomboideus, trapezius, and serratus cervicis muscles. Simultaneously, the latissimus dorsi and ascending pectoralis pull the humerus backward.
Unlocking Equine Power: Exploring Hindlimb Biomechanics 🐎
Protraction of the hindlimb: 🏇
This action gets a boost from hip flexion, stifle, and hock extension.
The iliopsoas muscles kick off hip flexion, with an assist from the TFL and rectus femoris. Together, these muscle groups flex the LS junction, lengthening the gluteus medius muscle, aiding in enhanced engagement.
Hindlimb extension finds support from the quadriceps as the stifle extends. The gastrocnemius and superficial digital flexor muscles extend the hock, while tendinous extensions of the DF muscles and the suspensory ligament support the fetlock.
Retraction of the hindlimb: 🏇
Flexion of hindlimb joints comes into play due to hip flexion (TLF, rectus femoris), rendering the iliopsoas muscle inactive. The caudal femoral muscles flex the stifle through the reciprocal apparatus, automatically flexing the hock and distal limb.
As the hindlimb extends backward, the gluteus medius contracts, while the quadriceps femoris extends the stifle and consequently the hock (via the reciprocal apparatus). The gastrocnemius muscle assists in extending the hock, while the digital extensor muscles simultaneously extend the phalanges.
End of Part 1. Stay tuned for Part 2 next week.
If you have any questions, please email me them below:
info@animalchiropractorukcom
Thanks,
Nika