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An Introduction to the Muscles of the horse and their uses.

Muscles of the forehand

Muscle / Ligament	*Origin / where the muscle starts*	*Insertion point; where the muscle starts*	*Action*	*Comment*
Massester; cheek muscle			Opens and closes the jaw. Allows chewing.
Brachiocephalicus Wide strap like muscle	Base of the skull behind the jaw	Below the point of shoulder to the humerus	Moves the head from side to side, pulls the scapula forward, raises it in collection, swings the foreleg forward.	Well developed for good movement. Too strong a rein contact stops free forward movement.
Sternocephalic	Jowl	Sternum	Moves the head and neck.	Over developed in ewe or bull necked horses, difficult to get into a relaxed shape.
Rhomboideus	Nuchal ligament	Scapula	Lifts shoulder and the forehand. Pulls the scapula forward.
Splenius	Behind the poll	Beginning of the Trapezius	Turns and extends the neck.	Makes up the top line if well developed.
Trapezius; flat sheet like muscle.	Occipital bone	Spines of the 7th cervical and all the Thoracic vertebrae	Lifts shoulder and forehand	If this is well developed the horse is working in a good outline.
Nuchal ligament	Poll	Withers	Helps muscles in the neck support the head
Deltoid	Scapula	Humerus	Flexes shoulder joint	If over developed it wil load the shoulder
Supraspinatus	Below the Trapezius	Point of shoulder	Maintains the shoulder in extension
Latissimus dorsi	Lower Thoracic vertebrae	Back of the humerus	Flexes the shoulder and pulls the foreleg back.
Triceps			Flexes the shoulder and extends the elbow
Biceps			Flexes the elbow and extends the shoulder
Pectoral			Helps pull the foreleg foreward.
Triceps Brachii			Extends the elbow joint
Biceps Brachii			Flexes the elbow joint
Extensor Carpus			Extend the knee
Flexor Carpus			Flexes the knee
Digital Extensor			Extends the toe and knee
Digital flexor			Flexes the toe and knee and extend the elbow.

Muscles of the trunk, back and ribs.

Muscles support the spine together with 3 ligaments and abdominal muscles.

Muscle or ligament	*Origin; where it starts*	*Insertion point; where it finishes*	*Action*	*Comment*
Spinalis Dorsi	Beneath thoracic part of Trapezius	4th cervical vertebrae
Lumbar muscles or Longissimus dorsi	Ilium	Vertebrae along the sine and the last 4 cervical vertebrae	Extends the spine and raises and supports the head, neck . Main muscle used in rearing, kicking, jumping and aids turning	Longest and strongest muscle, rider sits on them
Intercostal muscles	Spaces between ribs		Aids breathing
External and internal abodominal oblique	Attach to ribs and pelvic bones		Supports the internal organs
Supraspinous ligament	Poll	Sacrum	Supports head and neck, traction force aids support in weak thoracic lumbar area.	Spreads out, attaching to spines of the cervical vertebrae, Called nuchal ligament in the withers and neck area.

Muscles in the hindquarters.

Hindquarters are the engine of the horse, they should be well developed, strong to move the horse forward, particularly in the competition horse.

*Muscle or ligament*	*Origin; where it starts*	*Insertion point; where it finnishes*	*Action*	*Comment*
Superficial gluteal	Croup	Bottom of the hip attached to the sacrum	Flex and extend the hip, pulls hindleg toward the body, used for rearing, galloping and kicking	More developed in a dressage horse.
Biceps femoris	Behind gluteals	Bottom of the high attached to the patella and tibia	Maintains hip joint in extension	Main muscles over the hindquarters, part of the hamstring group, well developed in eventers, race horses.
Semitendinosis	Behind biceps femoris	Back of the hindquarters	Extends the hip and hock joints	Part of the hamstring group, well developed in eventers and race horses.
Semi membranosus				Part of hamstring group, well developed in race horses /eventers.
Gastrocnemius	Rear of the femur	Point of hock	Maintains hip extension
Peroneus tertius	Femur	Cannon bone	With superficial digital muscle moves the stifle and hock.
Achillies tendon	Gastrocnemius	Over point of hock
Sacrosciatic ligament	Sacrum and coccygeal vertebrae	Pelvic bone

Article provided by Hayfield Riding Centre