As humans, we stand with our spine near to vertical so that gravity compresses our spinal column.
Unlike us, a horse’s spine is near horizontal. His weighty abdominal and chest organs are pulled down by gravity, effectively hanging from the spine, and his heavy head is held out in front on the end of a long neck.
We then ask him to be an athlete, creating power through his body to connect the hindlimbs to the forelimbs, and finally we add the weight of a rider to the equation. Supporting these body parts and coordinating these levers — while all the time maintaining balance and energy — is a complex procedure for the horse, involving a range of muscles and nerves.
We are now more aware of the importance of core muscle development in providing the strong, stable base needed for correct movement and to prevent injury.
Power and lift
During each stride a horse’s back moves in flexion and extension, from side to side and in slight rotation.
The bigger the horse’s action — whether dressage or jumping — the more the body moves and the wider this range of movement. To prevent overstraining of any areas of the body, movement must be controlled and stabilised. A stable platform is vital so that the additional weight of the rider does not cause the back to overextend during the stride.
The horse uses both large and small core muscles to maintain this stability and move athletically.
Extension of the back occurs when the large muscles on the top of the back are contracted. The large muscles underneath the spine enable flexion of the back, support the rider and help counteract the pull of the abdominal contents. These are assisted by the muscles that flex the lumbosacral joint behind the saddle, including the iliopsoas muscles.
In addition to controlling the movement of the spine, the core muscles are important for raising the thorax (chest) of the horse relative to the floor — literally lifting the withers. Because the horse does not have a collarbone, the muscles that attach his forelimbs to his trunk must contract to create lift.
The stronger he is through his core, the more easily he can transfer power from his limbs through his body to perform movements or generate lift.
Poor core strength can result in a number of problems.
A very flexible young horse usually starts with a wide range of motion, giving a very elastic appearance. The more extravagant the action, the more critical core muscle development becomes to stabilise movement and protect the horse from injury.
Likewise, the less balanced the rider or the heavier they sit, the greater the risk to a horse with a very mobile and unstable back. If the back is extended too far, the dorsal spinous processes can impact on each other and form kissing spines.
Although we can see evidence of large muscle development through a good topline and a tight abdomen, the small muscles lying close to the spine are less visible. These include the multifidus muscles — vital for managing subtle movement.
When a horse is working correctly, the multifidus muscles become well developed because they are in constant use. When back pain occurs, however, the multifidus muscles are used less and tend to atrophy — becoming small and scarred, rather than functional.
Control of subtle movement for stability then decreases and the larger, less effective muscles are used. These become tense and can spasm, which can be felt by palpating the horse’s back.
Development of core muscle strength can be assisted by correct day-to-day management.
Encouraging the horse to have his head down and his back in flexion will stretch his topline and use core muscles. Simply feeding his hay and hard feed from the floor in his stable and encouraging turnout will help.
Stable-based exercises are useful for horses in work, following the principles of core muscle development. These include a range of baited (carrot) stretches, lifts, flexions and tail pulls, and are generally safest to do when a horse is already warmed up.
Groundwork exercises are particularly effective in switching on the correct muscle patterns without the strain and complication of a rider. These could include pole work at walk, exercise on a water treadmill or with a training aid such as a Pessoa. The maximum benefit is likely to be obtained by developing these exercises under the direction of a physiotherapist with an interest in core muscle development.
Ridden exercise with the horse’s back flexed and his head down will encourage correct posture and core muscle use, as will correctly performed downward transitions and half halts, pole work and gridwork. If the rider or saddle restricts the horse from lifting his back, however, he will be unable to perform the exercise correctly and will use the wrong muscles.
Tactile stimulators can be used under the direction of a physiotherapist to “remind” a horse to use certain muscle groups during exercise. Proprioceptive tape placed on the skin over selected muscle groups, or elasticated bands around the abdomen or quarters, can assist with switching on the right muscle groups.
Functional electric stimulation, under veterinary and physiotherapy direction, has been used effectively to improve patterns of core muscle use in some horses with back pain.
Ref: Horse & Hound; 15 October 2015