Sport Horse Strengthen the Sling Want your horse to achieve better collection? Help him strengthen the muscles of his thoracic sling. Second of two parts. By Hilary M. Clayton, BVMS, PhD, Dipl. ACVSMR, FRCVS ward from the inner surface of the shoulder blade to the ribs and the lower cervical vertebrae on each side. Besides raising the withers, serratus ventralis resists forward and downward motion of the trunk when the horse’s forelimb(s) are on the ground. In other words, it helps to prevent the horse from falling onto the forehand.
TERRAIN TRAINING: Walking on a downhill gradient is a “magic bullet” for strengthening the muscles of the horse’s thoracic sling
causes the withers to become more prominent between the scapulae. During locomotion, the sling muscles contribute to an uphill posture and to centering the horse’s chest between its forelimbs. Poorly toned or inactive sling muscles allow the forehand to slump between the scapulae, making the withers less prominent. The main component of the thoracic sling is a muscle called serratus ventralis, which runs down-
Another characteristic of serratus ventralis is that it is encased in a strong elastic sheath that stretches as the limb bears weight, then recoils as the limb pushes off. The elasticity cushions force transmission to the horse’s trunk (and ultimately to the rider’s back) when the limbs hit the ground during such movements as the extended trot, which involve rapid deceleration just after limb contact. In summary, we can think of the
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functions of the serratus muscle as: • Providing attachment of the forelimbs to the trunk • Determining how the forehand is suspended relative to the position of the forelimbs, both from front to back and from side to side • Lifting the forehand to put the horse in an “uphill” balance • Centering the forehand between the forelimbs after the horse has been straightened • Restraining the forehand in the face of decelerating forces that tend to tip the horse onto the forehand. Visualize the sling muscles acting in harmony on the left and right sides to support the forehand in an uphill balance, with the ribcage centered so the rider can sit in the middle of the horse with both seat bones supported equally. As you can see, a strong thoracic sling is necessary for good dressage performance. Fortunately, there are many ways of strengthening a horse’s sling muscles. Some exercises are done unmounted while others are performed under saddle. Read on to learn how.
Exercises from the Ground Many readers are already familiar with the use of core-training exercises to stabilize the horse’s core muscles. Owing to their role in positioning the horse’s chest, the sling muscles are considered part of the core musculature. I will describe how to perform the following unmounted exercises from the horse’s left side, but they should be done with an equal number of repetitions on the left and right sides. Even
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n my last “Sport Horse” column (“The Thoracic Sling,” January/ February), I looked at the structure and function of the muscles— known as the thoracic sling—that suspend the horse’s trunk from the weight-bearing forelimbs. In a standing horse, well-toned sling muscles improve the horse’s posture by raising the forehand, which
