27/09/2018
Hard ground and feeling “jarred up”…………a common complaint this summer!
Now the long hot dry summer is passing some horses are feeling the effects of this; hard ground increases the concussive forces to the joints and can lead to horses becoming jarred and restricted in their action. This may occur progressively over time or be a sudden acute response following an increase in impact such as competing on hard ground. Don’t forget the horse in some cases, is spending up to an additional 23 hours a day running around on this hard ground if on 24 hour turn out; this is also contributing significantly to the overall effect.
Horses may feel shorter striding, loose their action and elevation, may appear to be hugging the ground in their flat work or working over fences and coming in shorter to fences. They may show reluctance to go forward, showing less generosity, particularly over drop fences and the stride becomes tricky to find – hence the expression “jarred up”. These effects are compounded if the horse has underlying pathology susceptible to aggravation in these conditions. The joints will be exposed to increased concussion and can look puffy with a generalised filling to the lower limb and the horse maybe susceptible to splints or sore feet.
The thoracic sling muscles are responsible for creating elevation in the forehand; they suspend and elevate the thorax between the two scapulae and are engaged when absorbing and controlling vertical and horizontal forces through the limbs. The muscles of the thoracic sling are of particular interest amongst others, to the physiotherapist when a horse appears to be jarred up. When a horse is jarred up these muscles become shortened and hypertonic. Over time this can lead to adaptive postural changes, muscle imbalance and altered bulk to the key muscle groups.
The thoracic sling is a diverse arrangement of muscles relating to the neck, sternum, thorax and scapulae. It is interesting to note that the horse has no collar bone and elevation of the thorax is created and absorbed through these powerful muscles.
This is an interesting article by Hilary Clayton that explains the action of these muscles in more detail;
http://www.dressageheadlines.com/articles/dressage/significance-horse%E2%80%99s-chest-sling-muscles-biomechanic-research-hilary-clayton
Seventeen years of collecting data on gait analysis for dressage horses in the equine laboratory at the McPhail Center at Michigan State University, biomechanics research veterinarian Hilary Clayton, BVMS, PhD, DACVSMR, MRCVS, conducted studies to evaluate a horse’s body during collection.