Stretching and Relaxation

Myths and Reality

Jean Luc Cornille

After contraction comes relaxation. Both aspects of muscular work

create movements. The quality of the movement is not proportional

to the relaxation, but the intensity and timing of both the

contraction and the relaxation is. In most instances, the relaxation

is not a muscular slackness, but instead, a return to the initial

muscle tones. This is part of the stabilization mechanism which

rules proper functioning of the equine vertebral column. The same

mechanism stabilizes the human’s vertebral column. “The reflex

contractions of the spinal column muscles compensate for the

bending of the spinal column. This is a characteristic behavior of

the spine stabilizing system during human movement.” (Obber, J. K.

2002)

After a concentric contraction, the type that involves a shortening

of the contracting muscles, the muscles then relax and return to

their initial length. Technically, the muscles “stretch” as they

elongate. In the case of lowering of the neck, the upper neck

muscles elongate beyond their initial length. This is where myth is

separated from reality.

A lowering of the neck is in fact a flexion, which is achieved by a

concentric contraction of the lower neck muscles, and is aided in

the task by the force of gravity that pulls the head and neck down

toward earth. The upper neck muscles, situated above the cervical

vertebrae, elongate to allow the lowering of the neck, but also

contract to support the burden of the head and neck. When a horse

is under heavy sedation, the upper neck muscles do not resist

gravity and the horse’s head hangs a few inches above the ground

at the limit of the nuchal ligament’s elastic compliance.

The work of muscles that elongate while contracting is referred to

as “active stretching”. The work of the upper neck muscles is also

called “eccentric contraction”. In terms of muscular work,

eccentric contraction is the most powerful type of muscular

contraction. “Muscles working eccentrically can absorb up to 15

times more energy than during concentric contractions.” (R. C.

Payne, P. Veenman and A. M. Wilson, 2004)

The myths suggest that as the horse lowers his neck, the upper

neck muscles stretch while relaxing. But in reality, the upper neck

muscles elongate as well as support the burden of the head and

neck, which is as much as 10% of the horse’s body weight. Hence,

they do not stretch and relax, but work in active stretching, i.e.,

eccentric contraction.

“Everything should be made as simple as possible but not

simpler.” (Albert Einstein) Stretching theories are simpler. They

involve two main muscle groups, the Longissimus dorsi, which

connect the sacral vertebrae to the middle of the neck, (cervical

vertebrae,) and the Spinaleus dorsi which extend from the wither

back along the vertebral column. Both terms are generic. The

longissiumus system is in fact composed of several muscles,

longissimus cervicis, capitis, lumborum, ect. Oriented in mirror

image direction is the spinaleus system that refers to muscles such

as the multifidius which fascicles are oriented downward and

backward. Downward, means that the fascicles are oriented from

the dorsal spinous processes down to the body of a vertebra

situated three to five vertebrae behind. Backward, means that the

fascicles are oriented toward the back.

Simplistic representations illustrate the longissimus system as a

long and thick bungee cord stretching from the sacrum to the

fourth cervical vertebra. Based on such schematic illustration

simplistic thoughts deducted that the lowering of the neck

elongated the horse’s whole top line.

A slightly more elaborated illustration of the longissimus system as

the one presented in 1946 by the Dutch scientist L.J. Slijper,

demonstrates that such simplistic theory does not apply to the back

muscles’ structure. The longissimus dorsi muscle group is

composed of fascicles bridging three to five vertebrae.

Therefore even if the upper neck muscles were pulling down and

forward on the back muscles, as claimed by stretching theories, the

effect would not go further back than the whither area.

Furthermore, if the upper neck muscles were pulling on the back

muscles down and forward, they would not be able to support the

burden of the head and neck. The horse’s head would then hang a

few inches above the ground at the limit of the nuchal ligament’s

elastic compliance, as demonstrated by the horse under heavy

sedation.

On the picture, the horse is prepared for the dentist and the effect

of the sedation is only starting.

The same horse holding a similar neck posture while not under

sedation shows a very different work of the upper neck muscles.

Even myths have their logic, however, and the belief that the

lowering of the head and cervical vertebrae pulls on the back

muscles, thereby stretching and relaxing the horse’s top-line, is

supported by the feeling of ease that is often associated with work

with a longer neck posture. The horse’s vertebral column does feel

more “round” and at ease when the neck is held in a longer

posture. The problem is not the accuracy of the rider’s perception

but rather the translation of the perception. The feeling of ease

does not result from relaxed elongation of vertebral column

muscles but instead from the way the vertebrae rotate in relation to

each other. The phenomenon is known as “Instant Center of

Rotation.”

Vertebrae rotate around each other, and if a study is made of just

two vertebrae of the equine spine, one would focus on an area that

scientific research defines as inter-vertebral joint complex, or

motion segment. “The functional unit in spinal kinematics is the

„inter-vertebral joint complex‟ or „motion segment‟, which is

composed of two contiguous vertebrae and their associated soft

tissues.” (Denoix)

Using a geometric model, the rotation arc of one vertebra around

the other can be described as the segment of a circle. The axis of

rotation of the rotating vertebra is situated toward the middle of the

previous vertebral body.

On this picture, the vertebral rotation that creates longitudinal

flexion of the spine is illustrated in red. The vertebral rotation that

creates extension of the spine is illustrated in green.

The theoretical center, wherein one vertebra rotates around the

other can be labeled “center of rotation”.

In our example, however, the central vertebra is fixed, while in

motion, this vertebra is also rotating around the previous vertebra

and therefore, the center of rotation can only last an instant. This is

why it is labeled “instant center of rotation”. When the neck is

lowered, the instant center of rotation moves down and forward

toward the inter-vertebral disk.

If one compares the rotation of one vertebra around the other as the

horse’s neck is held in a natural posture, with the rotation of the

same vertebrae when the neck is lowered, we can observe less

pressure on the lower end of the inter-vertebral disk. “The inter-

vertebral disk undergoes less tangential displacement (shearing)

than during thora-columbar flexion alone”.(Denoix)

The pressure on the inter-vertebral disk is quite impressive. This

picture illustrates the bulging that occurs in the lower end of inter-

vertebral disc during flexion of the lumbo-sacral junction.

The yellow arrow is directed toward the bulging of the

intervertebral disk .

The vertebral body on the left is the 6

th Lumbar vertebrae and the

vertebral body on the right is the first sacral. For comparison, the

same vertebral segment is pictured during extension of the spine.

(Power part of the picture.) The intervertebral disk is then stressed

differently

Watching the stress that a simple flexion of the vertebral column

induces on the lower end of the inter-vertebral disks may help to

understand the salient function of the back muscles. The whole

muscular system surrounding the horse’s vertebral column is

designed to primarily protect the spine from intensity and

amplitude of movements that would exceed the spine’s integrity

and possible range of motion.

Greater stress on the vertebral structure stimulates stronger

protective reflexive contraction of the surrounding muscles, while

less strain incurs less muscular intensity. The feeling of ease

associated with a lower neck posture may results from the

adjustment of the epaxial spinal musculature to lesser stress on the

vertebral structure. Lesser contraction might be described as

relaxation but the meaning is quite different from the concept of

relaxation that suggests looseness and elongation of the back

muscles.

Nicole Barthel, who translated General Decarpentry’s Academic

Equitation into English wrote in her preface, “Relaxation: The

French use the word „decontraction‟, as the opposite of

contraction. From the point of view that concerns us in equitation,

I would have preferred this term to „relaxation‟, but it would not

have been condoned by English linguists. Wherever the word

„relaxation‟ occurs, it must be understood that it signifies an

absence of sustained contraction and not a total slackness of

muscles”. (The French definition of “decontraction” is absence of

unnecessary contraction)

There have been many instances in history where it was

demonstrated subsequently that a situation was not as perceived.

The feeling of ease associated with lowering of the neck does not

result from looseness and elongation of the back muscles. Instead,

the feeling of ease results from better orchestration of numerous

and minuscule muscle contractions and compensatory contractions

that create the rotations of the vertebrae. As well, gaits and

performances cannot be enhanced increasing the horse’s vertebral

column’s range of motion. Rather, performances and soundness

rely on the rider’s ability to properly coordinate the minute

motions of the horse vertebral column.

The perception of a rounder back is the outcome of the thoracic

flexion that can be created by a slight lowering of the neck. “The

lowering of the neck provoked flexion all along the thoracic

spine.” (Jean Marie Denoix, DVM. PhD, 1999) However, the thoracic

flexion does occur only if the lowering of the neck is treated as a

cervico-thoracic flexion, which is the combined work of the

muscles suspending the trunk from the front legs (Thoracic) and a

longer and consequently slightly lower neck posture (Cervical).

The difference between cervico- thoracic flexion and lowering of

the neck is illustrated here. Within approximately the same neck

posture, the horse sustains the trunk between the shoulder blades,

(left picture.) The horse sags then the trunk between the forelegs,

(right picture.)

We superimposed the two pictures placing on the back the horse

sustaining the trunk higher between the forelegs. The yellow doted

line follows the top line of the horse sustaining the trunk higher

between the forelegs. The green doted line follows the top line of

the horse sagging the trunk between the front limbs.

Due to the traction that the nuchal ligament exerts on the tip of the

dorsal spinous processes of the wither’s vertebrae, the lowering of

the neck induces a “verticalisation of the dorsal spinous process”

If the horse sustains the trunk between the forelegs, (Cervico-

thoracic flexion), the verticalization of the dorsal spinous processes

of the wither induces flexion of the thoracic spine. By contrast, if

the horse lowers the neck without adequate work of the muscles

supporting the trunk from the front legs, the lowering of the neck

cumulates damaging effects, increased weight on the forelegs, lost

of mobility of the lumbar vertebrae, restricted dorso-ventral

rotation of the pelvis.

The father of modern equitation wrote: “Theories teach us to base

our work on sound principles, and these principles, rather than

being opposed to what is natural, must serve to perfect nature with

the aid of art”. (Francois Robichon de la Gueriniere, 1731) Riding and

theirs professing greater amplitude of the horse’s vertebral column

movements via stretching and relaxation are opposed to what is

natural. Perfecting nature demands a subtle orchestration of the

myriad minute muscle contractions and compensatory contractions

that are the source of all body movements. “The biomechanics of

the vertebral column, although very complex, are of vital

importance because they form the basis of all body‟s movements,” (Leo B. Jeffcott, 1980)

The subtle orchestration of the minute and numerous muscle

contractions and compensatory contractions creating the work of

the horse’s vertebral column is mostly by the horse’s central

nervous system, the brain. It would be impossible to stimulate and

coordinate such complex mechanism through the traditional

concept of “stimulus response”. Guiding the horse’s brain toward

the most efficient body coordination demands understanding and

respect for reality. The horse’s brain may eventually explore

muscular coordination beyond the scope of natural reflexes, but

will resist amplitude of movements which exceed his vertebral

column’s possible range of motion. Hence, the horse’s brain will

protect his spine from stretching, muscles’ elongation, and

relaxation in the sense of loosing muscle tone.

The amplitude of the vertebral column’s movements is naturally

very limited and the main function of the back muscles is to

maintain the movements of the vertebral column within the limits

of the vertebral column’s range of motion. “Electromyographic

studies and movements data presented above strongly suggest that

the primary function of the back muscles during walking is to

control the stiffening of the back rather that to create movement.” (Hans Carlson, 1979)

These are the realities that the horse’s brain is designed to protect

and efficiency demands that riding and training principles adjust to

reality. In motion, considerable forces are induced on the horse’s

vertebral column. There are the forces created by the legs,

accelerations of gravity, inertia, rider’s movements, etc. The

vertebral linkage is designed to absorb, convert, and redirect these

forces while simultaneously maintaining amplitude and intensity of

the vertebral column movements within the limits of the vertebral

column’s range of motion.

Fundamentally, a large amount of forces have to be absorbed and

minimized within the limits of the equine vertebral column’s range

of motion. Simultaneously, great deals of diverse and minute

movements have to be orchestrated within these limits. “The

amount of joint range of motion at any vertebral motion segment is

small, but the cumulative vertebral movements can be

considerable.” (Kevin K. Haussler, DVM, DC, PhD, 1999) Therefore

the work of the back muscles is to reduce forces and movements

through supple resistance.

Our ancestors believed that the movements that they perceived on

the saddle were the motions of the horse’s vertebral column. Until

technology demonstrated otherwise, such belief was effectively the

most rational explanation. Today’s measurements demonstrate that

a large percentage of the movements, or “ kinematics”, that the

rider perceives on the saddle are in fact perceptions of forces, or

“dynamics”. “Kinematics is the geometry of movement, a

graphical record of the initial, intermediate, and final positions of

the various parts and pieces of the system – one in relation to the

other. Dynamics, on the other hand, is concerned with the forces

applied to and generated by the system and, therefore, includes

acceleration, mass, potential and kinetic energy, momentum, etc.”

(James R. Rooney,DVM, 1969)

This diagram shows the amount of vertical forces impacted on the

rider’s physique at a slow trot. The dots moving the most are

situated under the rider’ seat. Each dot represents a sensor,

(accelerometer), that was fixed on the horse’s back. The line

connecting the dots illustrates the forces placed on the horse’s

thoracolumnbar spine during locomotion. The computer program

was set to measure exclusively the vertical forces. The area that is

subjected to the largest amount of vertical force is the area where

the rider is seated. The sensors record the sum of the vertical

forces, which includes the upward propulsive forces developed by

the front and rear legs, as well as the vertical forces created by the

rotation of the vertebrae.

Under normal circumstances, the forelegs develop 57% of the

vertical forces while the hind legs produce only 43%. These

measurements focus exclusively on the limbs’ action. “In horses,

and most other mammalian quadrupeds, 57% of the vertical

impulse is applied through the thoracic limbs, and only 43%

through the hind limbs.” (H. W. Merkens, H. C. Schamhardt,G. J. van

Osch, A. J. van den Bogert, 1993).

To date, measurements differentiating the action of the limbs and

the vertical forces created by the rotations of the vertebrae have not

been achieved. We have observed through our approach that it

was effectively possible to modify the horse’ limbs kinematics

through specific orchestration of the horse’s vertebral column

mechanism. However, such control demands adapting riding

principles to actual knowledge. Principles of riding such as driving

the horse onto the bit and swinging motion of the rider’s lumbar

vertebrae, (doughy seat), are based on elementary knowledge of

the equine physiology. These principles do not permit any

sophisticated control of the horse’s vertebral column properties.

By contrast, riding principles based on actual knowledge of the

equine physiology promote reducing the sum of the forces induced

onto the rider’s physique by the horse’s movements through supple

resistance of the rider’s vertebral column muscles. “The subtle S-

curve of the spine allows the spine to oscillate minutely, a

movement so tiny hat it is hardly perceptible to the naked eye,

producing a “soft” seat. This “soft seat” differs fundamentally

from a “doughy” seat, in which we find a spine that is too flexible

and allowed to undulate freely in response to the horse‟s

movement.” (Waldemar Seunig).

Already in 1964, equine research studies suggested that the

rotations of the vertebrae were converting the thrust generated by

the hind legs into horizontal forces, (locomotion), and vertical

forces, (resistance to gravity), “An initial thrust on the column is

translated into a series of predominantly vertical and horizontal

forces which diminish progressively as they pass from one

vertebrae to the next” (Ricahrd Tucker, 1964). The findings strongly

suggest that equestrian theories such as the lowering of the neck

were too primitive. Even if the lowering of the neck had an effect

on the back muscles, it would be a general action. Instead,

efficiency in forward movement and balance control demands the

faculty to discriminate specific areas and movements. The rider’s

back, rather than any neck posture, influences efficiently the

horse’s vertebral column mechanism.

In 1946 E. J. Slijper investigated the insertion of the main back

muscles on the dorsal spinous processes of the vertebrae. The

Dutch scientist may not have been the first to think that the

muscles were rotating the vertebrae through their action on the

dorsal spinous processes, but he was the first to thoroughly assess

the hypothesis. Slijper compared many different species in order to

soundly determine the function of each muscle. The scientist even

raised a goat which was born with only two hind legs. Later,

Slijper euthanized the two legged goat and compared the angle of

the goat’s dorsal spinous processes by comparison with the dorsal

spinous processes of a normal goat. The bipedal goat allowed him

to demonstrate that his hypothesis was right. Slijper believed that

the angle of the dorsal spinous processes of the vertebrae was

influenced by the action of the muscles acting on the dorsal

spinous processes.

Slijper‟s diagram compares the vertebral column of the bipedal

goat with the vertebral column of a normal goat.

Slijper’s work demonstrated similarities between all terrestrial

mammals but also offered specializations related to the animal’s

size, gaits, and survival needs. Slijper (1946) already established,

as did James Rooney (1969), Kevin Haussler (1999) and others,

that the main back muscles were set and functioning in opposite

direction. Therefore, vertebral rotations are created, measured,

compensated, and specialized, by the subtle coordination of

muscles acting in opposite directions.

The findings should have raised a few rational thoughts. First, it is

very unlikely that a neck posture acting on the back muscles in a

single direction would be able to coordinate muscles groups

working in opposite directions. In the same line of thought, riding

principles emphasizing shifts of the rider’s weight acting back to

front are unlikely to properly coordinate muscles groups such as

the main muscles of the horse’s back, which are acting in opposite

directions.

The topic of this series, “a failure of Olympics dimension,” offers

that by failing to evolve with recently advanced knowledge of

equine physiology, riding and training techniques are leaving

equine athletes unprepared for the performances.

Riders’ skills and horses’ talents deserve better riding and training

techniques than driving the horses into an overly flexed neck.

Many great riders have found efficient solutions but their legacy

cannot be understood as long as one’s thinking remains at the level

of driving the horses onto the bit.

The purpose of this series is to provide the knowledge to

discriminate riding and training principles that efficiently prepare

the horse’s physique for the performance from riding principles

that fail the horse’s talent and exploit the horse’s generosity until

there is impairment.

Jean Luc Cornille

References;

- ( Obber J. K. 1074, A dynamic concept for the diagnosis of

idiopathic scoliosis. In: Biomechanics IV. Proceedings of the 4th

International Seminar of Biomechanics. Eds R. C. Nelson & C. A.

Moorhouse, Mcmillian Press Ltd, London & bastingstoke)

- (R. C. Payne, P. Veenman and A. M. Wilson, The role of the

extrinsic thoracic limb muscles in equine locomotion, 2004. J.

Anat. 205 pp479-490)

- (Jean Marie Denoix,DVM, PhD, Spinal Biomechanics and

Functional Anatomy, The Veterinary Clinics of North America,

Back problems, Volume 15. Number 1. April 1999)

- (Nicole Barthel, Translation of General Decarpentry‟s Academic

Equitation, 1971)

- (Francois Robichon de la Gueriniere, Ecole de Cavalerie, 1731)

- (Leo B. Jeffcott, Natural rigidity of the horse‟s backbone, 1980)

- (Hans Carlson, Halberstma, J. and Zomlefer, M. 1979, Control of

the trunk during walking in the cat, Acta physical, scand. 105,251-

253)

- (Kevin K. Haussler, DVM, DC, PhD, Anatomy of the

Thoracolummbar Vertebral Region, 1999)

- (James R. Rooney, Biomehcanics of lameness in horses 1969,The

William & Wilkins Company, Baltimore)

- (Richard Tucker, Contribution to the Biomechanics of the

vertebral Column, Acta Thoeriologica, VOL. IX, 13: 171-192,

BIALOWIEZA, 30. XL. 1964).

- (E. J. Slijper, 1946. Comparative Biologic-Anatomical

Investigations on the Vertebral Column and Spinal Musculature of

Mammals. Institute of veterinary anatomy of the state university,

Utrecht, Holland. Tweede Sectie, Deel XLIL, Nº 5)

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- (Leonardo da Vinci, 1452-1519)

- (Francois Robichon de la Gueriniere, Ecole de Cavalerie, 1733)

- (General Decarpentry, L‟Equitation Academique, 1949)

- (Mikael Holmström, Quantitative studies on conformation and

trotting gaits in the Swedish Warmblood riding horse,

Dissertation, Uppsala, 1994)