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The anatomical and physiological bases of en dehors





















The term en dehors, which literally means "outside", means the movement of external rotation of the hip capable of modifying the orientation of the entire lower limb, so that the toes are facing laterally and not forward. This attitude is the basis of all the movements of classical dance and allows you to perform the five basic positions of the feet.


A good performance of the en dehors is part of the correct setting of the dance students and conditions the achievement of the majority of both technical and artistic objectives; from the medical point of view, moreover, the difficulty to adequately perform the movement in question represents the main cause of risk for the onset of a high number of pathologies due to functional overload of the lower limb. In this article we will focus on analyzing the conditions that allow to obtain a correct en dehors while, in the next article, we will focus on all the problems related to the limitation of external rotation of the hips (en forced dehors or overturn).


The amplitude of the external rotation movement of the hip is different from individual to individual and is closely linked to innumerable structural and functional factors:


a) Position of the pelvis: the acetabulum, located on the external face of the pelvis at the junction of the ilium and pubis, is the cavity in the shape of a "cup" within which the head of the femur must rotate. Its orientation in space obviously changes with the movements of the pelvis itself: so that the head of the femur can easily perform external rotation, the pelvis must be kept in a neutral position, ie neither tilted forward nor backward.


The neutral position of the pelvis provides, in fact, that the muscles of the trunk (abdominal and dorsal) are activated and work in synergy with the muscles of the pelvic floor and with the diaphragm: in this way the load on the femoral heads is reduced and yes creates the optimal condition to facilitate mobility.


 


b) Angle of anteversion of the femur: the head of the femur has the shape of a sphere and is oriented upwards, inwards and forwards with respect to the frontal plane. This means that when a subject is lying in a supine position, the head of the femur is not parallel to the floor but looks slightly towards the ceiling and forms, with the support base, an angle called precisely the angle of anteversion of the femur, which can vary between 10 ° and 30 °.


The width of this angle is inversely proportional to the ability to rotate the hip out: the subjects who, having an anteversion angle of about 10 °, are able to carry without effort at 180 ° between them. On the other hand, subjects who have a wider anteversion angle (about 30 °) will not be able to bring their feet out by orienting them exactly 180 ° apart without compensatory movements on the knee and foot. The constant use of this type of forced movement represents one of the most important causes of spinal overload and lower limb patriques associated with the study of classical dance. For this reason it is of fundamental importance that dance teachers teach their pupils, from an early age, to work in compliance with their "physiological en dehors": the toes look in the direction allowed by the movement of the hip and the center of the patella constantly corresponds to the second toe.



It is clear that using this type of approach to movement does not mean "giving up" at the start and not trying to improve one's own dehors: what must be clarified is that the skeletal component cannot be modified with training and that efforts of the dancer must be focused on optimizing muscular work and proprioceptive control, thus obtaining the best possible en dehors, without forcing the articulation of the hip beyond the allowed limits.

c) Activation of the deep rotator muscles of the hip: traditionally, in most dance classes, the external rotation of the hips is associated with the contraction of the gluteal muscles and, more specifically, to the action of the large gluteal muscle, the largest the most superficial of the three gluteal muscles. From the functional point of view, instead, in order to be able to perform the external rotation movement of the hip in all the width allowed by the skeletal structures described above, it is necessary that the rotator muscles act in a very precise sequence. The initial phase of the external rotation of the hip is given by the contraction of the pelvis-trochanteric muscles, six small deep muscles that lie below the buttocks on the posterior aspect of the pelvis and which, with an almost horizontal course, connect the skeleton of the pelvis to the great trochanter of the femur.


The contraction of the gluteus maximus muscle, never massive but aimed only at "maintaining" the femoral head in external rotation, serves above all to stabilize the position reached thanks to the action of the deep muscles. It is of fundamental importance to note that, if the gluteus maximus muscle contracts first, it blocks the external rotation movement of the hip by moving the entire pelvis in retroversion.


At this point in the speech we must clarify that when we speak of en dehors we do not refer to a "position" but to a "movement": this means that once the result is achieved (the tip of the feet turned outwards), this it must also be maintained. For this it is necessary to use the action of the adductor muscles of the hip that attract the inner face of a thigh towards the contralateral like a magnet and the thrust of the sole of the foot on the ground that "repels" the floor involving the entire lower limb in the work, like a corkscrew planted in the floor.


            From all that has been said up to now it is clear that every dancer must be aware, from the first years of study, of his ability to rotate his hips externally, focusing not only on the global extent of the movement but also on the possible differences in mobility between one hip and the other that are far from rare and still condition the execution of the positions of the feet. Among all the types of tests proposed for the evaluation of external rotation of the hips, we believe that the most reliable and simple to perform is the passive test in a prone position in which the teacher or physiotherapist is the one who, with the subject completely relaxed, moves the lower limb with the knee flexed 90 ° in and out with the leg moving like the rod of a metronome.


            This simple maneuver can highlight the presence of a large and fluid movement in subjects "naturally rotated" or an early arrest of the movement of external rotation of the hip with different types of resistance to the attempt to continue the movement itself: in the latter case the 'Dance teacher will have to watch with particular care that the student does not get into the habit of compensating for the lack of hip rotation by building the en dehors movement from the bottom upwards, using compensations at the knee and foot level. Only in this way, in fact, the alignment of the lower limb will be respected without producing excessive strain on all its joints.

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