Postural system throughout lifecourse

 “The postural system is an automatic system that assumes the constraint of maintaining the body in the vicinity of a fixed position defined in relation to the environment“, wrote Villeneuve in 1989. Bipedalism is only one aspect of the postural system which, in homo sapiens, has adapted to the verticality and gravity of the earth. Cosmonauts have proven that it also adapts to the absence of gravity in space.

 Since the work of Jean Pierre Flourens on the bipedal pigeon that became scoliotic after labyrinthine destruction, many studies have confirmed the links between scoliosis and the postural system. Even if we do not know for sure if it is a cause, it is admitted that scoliosis disturbs the vertebral proprioception. It is on this basis that Charles Gabriel Pravaz associates exercises to stimulate the postural system with the mechanical correction of scoliosis.

 The history of the postural system was described in 2018 by Ivanenko.

 The discovery of muscle tone dates back to the 16th century. It was not until the beginning of the 20th century that Sherrington defined the bases of postural regulation. The control of balance dates from the end of the 20th century and it is only recently that the chaotic system of the inverted pendulum and postural stability were described by Winter. In 1996 de Mauroy was the first to speak of chaotic scoliosis in his book: "La scoliose traitement orthopédique conservateur".

 In 2012 MacPherson and Horak clarify the fluctuations of the center of pressure in quadrupedia and bipedalism.

 More recently in 2019, Marzena Wiernicka confirms poorer postural stability in adolescent girls with scoliosis that is accentuated in right monopodal stance.

 The postural system acts directly on human biomechanics and indirectly through the adaptation of biomechanics to the environment.

 The maintenance of the posture requires:1. a permanent adaptation of postural tone,2. a static component with stabilization of this posture oscillating around the cone of economy,3. a cognitive component of body schema.

 The control of the postural system will develop with a progressive physiological maturation of the different components of the postural system: vision, vestibular, proprioception... At the same time, the subcortical integration areas develop strategies according to the environment and the tasks to be performed.

 The development of afferents, the maturity of integration centers and the myelination of extrapyramidal tracts evolve in parallel during growth. They interact permanently and allow for an adaptation specific to each individual. It is possible to guide them through physiotherapy.

 Massion in 1994 assimilated the control of the postural system to a summation of postural reflexes. The sensory-motor modulations or reflexes are dependent on the environmental context with a permanent oscillation between anticipation or feedforward and feedback. The automatic postural reactions are accomplished in accordance with the internal representation of the body schema. The elements of the body schema already exist at the level of the spinal cord and contribute to the processing of sensory data and to postural responses. Postural control is the result of multiple interactions integrating the musculoskeletal and nervous systems, the demands of the task and the variations of the environment. The result of the multiplicity of these interactions becomes motor skill. The objective of the Lyon Method is to improve these motor skills by acting on the entire system.

 Posture and tone are the basis of the organization and execution of the praxis: a movement cannot be executed without an adapted posture. Postural tone represents the tonic activation of muscles in order to provide specific postural attitude and generate force against the ground to keep the limbs extended. Postural tone is commonly viewed as low-level muscle tension observed in both distal and proximal (trunk and neck) skeletal muscles. Postural attitude is determined by both individual morphology and specific low-level muscle activity, Integration of several sensory and motor areas has developed through millions of years of life evolution with the purpose of providing accurate regulation of body orientation in the gravity field.

 This permanent tension of the postural tone is the basis of the Lyon Method's concept of tensegrity. Scoliosis creates a tension asymmetry between concavity and convexity by the simple modification of the muscular leverage arms. Plastic deformation aims to rebalance and reprogram the receptors into the most corrected position possible. In addition, during pubertal growth there is no muscular deficit, but there is a physiological hypotonia that hinders the action of the postural system at the musculature level. Physiotherapy and sports will counteract this hypotonia by strengthening the type I fibers.

 In 2016 Knight extended the sliding filament theory of muscle contraction to include regulatory and cytoskeletal proteins responsible for the nonlinear viscoelastic properties of muscle and the economy of force production that are key peripheral contributions to postural regulation.3 sliding filaments Actin, myosin and titin. Titin appears to have all the characteristics necessary to explain the static stiffness properties.

 In addition to Tonus adaptation, the Lyon method acts directly on maturation and chaotic approach to posture development. It intervenes indirectly on the predictive and anticipatory approach by the association of adapted sports activities.

 The maturation approach was developed in 1978 by Hillingworth. It is based on 6 principles; 1. it is a continuous process from conception to maturity, 2. the sequences are identical for all children, 3. it is linked to extrapyramidal maturation, 4.) it allows for the individuation of responses, 5. it progresses according to the cephalo-caudal law, 6. reflexes must disappear for voluntary movement to appear

 Throughout growth there are major stages. The stabilization of the pelvis, which is essential for walking. The stabilization of the head with its lateralization around 7 years old. At the age of 12, proprioceptive maturity at the level of the spine. The tracts of the extrapyramidal system will also follow a chronological development: reticulo, vestibulo, tecto and rubro-spinal. The exercises will be adapted taking into account this chronological progression during growth.

 The evolution of the postural system is a key element in psychomotor development. It is this maturation that will allow the child to progressively reach the seated position and then the erect position, to free the mobility of the shoulder and the hand, to orientate his body and within the framework of his expressive function, to initiate interactions. These acquisitions are the source of perceptive, motor, cognitive, affective and social development. Some characteristic motor elements of postural development are developed in this table. Bicycling and swimming before the age of 7, acquisition of body schema at the age of 9. Speed, precision and coordination until the age of maturity at 12 years. Endurance, strength and resistance continue to develop until age 16.

 Infantile scoliosis is often accompanied by cranial plagiocephaly, which may be a cause of asynchronism of cephalic receptors contributing to postural tonic control of the head during the first 3 months of life.

 During the first year of life, the prerequisite for organizing the control of locomotor balance is the stabilization of the pelvis. Once this stability is acquired, it is possible to observe 2 organizations in the maintenance of the balance: A descending organization from the head or pelvis to the feet until the acquisition of verticality. An ascending organization that starts from the feet or the pelvis towards the head until the acquisition of an adult-like gait before the age of 7 years..

 Assaiante in 1998 show that the pre-requisite to be able to organize the control of locomotor balance is the stabilization of the pelvis. The first year of life shows all the stages of this articulated descending organization. The referential of postural control is gravity.

 From 1 to 6 years, it is an ascending organization in block from the pelvic center of gravity to the head. It is the reticulo-spinal tract that is solicited in the sagittal plane of function. The egocentric frame of reference is the whole body. In scoliosis, adapted exercises can improve the development of postural anticipation. At age 2, standing. At 4 years old, toes up. At age 6, coordination with the corrective movement.

 The stabilization of the head in space in all 3 dimensions will serve as the basis for a descending organization of postural control. The age of 7 years, which is the age of lateralization, is considered a pivotal period in the evolution of balance strategies.

 Three-dimensional stabilization of the head occurs with lateralization around the age of 7 years and vestibular maturity. This integration of the horizontal and vertical semicircular canals is the basis for the three-dimensional descending organization of postural control. It is the vestibulo-spinal tract that is then called upon. The egocentric frame of reference is the segments.

 From 9 to 12 years of age, the postural system integrates vision with maturation of the tecto-spinal tract. The scapular girdle and the upper limbs can then compensate for vertebral asymmetries. The allocentric frame of reference is the external world,

 The maturity of the spinal proprioceptive system is reached around the age of 12. In scoliosis, there is a lack of use of proprioceptive information. Some authors also point out a delay in the integration of visual information. It should be noted, however, that the postural system is redundant and the integration circuits can compensate each other.

 This discordance and the frequency of scoliosis in girls confirms the major importance of the maturity of the vertebral proprioceptive system in the genesis of scoliosis. Pubertal vertebral growth begins before the average age of maturation. Burwell described this mechanism as Neuro-Osseous Timing of Maturation (NOTOM).

 This discordance and the frequency of scoliosis in girls confirms the major importance of the maturity of the vertebral proprioceptive system in the genesis of scoliosis. Pubertal vertebral growth begins before the average age of maturation. Burwell described this mechanism as Neuro-Osseous Timing of Maturation (NOTOM).

 Under the age of 40 and despite pregnancies, the situation is almost stable. The postural system manages the family, professional and sports environment as well as possible. After the age of 40, the aging of the anatomical structures accentuated by scoliosis imposes an adaptation to the postural system. The main stages are :1. the sarcopenia of scoliosis from the age of 40 with a decrease in type II fibers. 2. Then, up to the age of 55, the disturbance of visual and vestibular integrations. 3. Between 55 and 75 years of age, cognitive integrations are slower and will be re-educated by dual task exercises.4. The ultimate evolution is the degeneration of type I fibers with the Pisa syndrome and camptocormia.

 The evolution of posture is a key element in psychomotor development. It is this posture that will allow the child to progressively reach the seated position and then the erect position, to free the mobility of the shoulder and the hand, to orientate his body and within the framework of his expressive function, to initiate interactions. These acquisitions are the source of perceptive, motor, cognitive, affective and social development. Some characteristic motor elements of postural development are developed in this table.

 The aging of anatomical structures leads to a functional vicious circle. Muscle weakness, Orthopedic constraints, Sensory impairment with distorted or missing information Vision: distant contrats sensisitivity & depth perception, Vestibular function, Proprioception: plantar tactile sensitivity. But Allison et al. (2006)’s result suggested that, even in higher age, the plasticity of sensorimotor processes and especially of multisensory integration is preserved.  Sufficient peripheral sensation allowed intra- and inter-sensory reweighting similar to young participants. 

 Sarcopenia is a loss of muscle mass that reaches 20% by age 70 without scoliosis. Scoliosis will accentuate sarcopenia. Weight training must be measured out, for example by avoiding crossfit and by avoiding strengthening the quadriceps and glutes, which increase pelvic retroversion. These well-dosed exercises, done regularly and consistently, on a daily basis, bring into play all afferent, visual, vestibular and proprioceptive components, as well as strengthening muscles, and of course cognitive performance, if systematically combined with a double task of mental work, have a preventive effect.

 Detect and, if necessary, correct any degradation of intrinsic (intracorporeal or somatic) factors from age 45 years; these include vision, vestibular function and balance, proprioception, and psychological and neurological status. For the vision, the lighting must be uniform by increasing the brightness and decreasing the contrast. Beware of polarized lenses that are not compatible with the LCD screens of modern cars. At night, night lights are recommended.

 The vestibular integration will be favored by unipodal supports of 5 seconds alternating right and left. Golf practice is ideal at this age.

 The decrease in proprioceptive afferences will be compensated by regular walking with shoes adapted to the ground. The proprioception of the feet can be compensated by using a stick with a handle adapted to stimulate the Tactile biofeed back of the hands like haptic supplementation. The environment will also be modified by avoiding carpets and slippery surfaces.

 The dual task involves combining the exercise with an intellectual task such as counting backwards starting at 100 or keeping a tray or stick level.

 Many specific techniques can improve control such as stochastic resonance which has been found to lower sensory thresholds. This technique ameliorates sensory integration and, consequently, postural stability.

 Posture and movement are closely linked: the realization of a successful and harmonious gesture cannot be freed from an active and effective maintenance of the posture (Massion et al., 1999). This posture-movement association is made possible by the presence of multiple internal representations, in particular the body schema, the representations of the action to be performed and a representation of the environment in which the action is performed. Thanks to the integration of different sensory information, whether visual, tactile, proprioceptive or vestibular, these representations are constructed and updated throughout life.

 The second approach is a non-linear chaotic approach that complements the maturation delay of the postural system. The Lyon method takes into account this approach for scoliosis of less than 20°. For Gibson, gesture thus emerges from an interaction between the environment and the organism. For Bernstein, synergy allows the ordering of behavior from a spatiotemporal point of view. According to Zanone (1990), the dynamic perspective is non-linear. An organism, whatever its initial state, is always oriented towards a stable and stationary state called the "attractor" of the system's behavior. The attractor results from of an interaction between the environment and the organism. During an imbalance, the system becomes active, chaotic, then finds an attractor: either the initial one if the system is stable, or another one and it is a transition of phase, if the system is flexible.

 In growing scoliosis, the interaction with the environment occurs before the deformation of the vertebral body. The difficulty of scoliosis is the passage beyond 25° from deviation to deformation. The initial deviation becomes a structural deformity with the onset of a vicious biomechanical cycle described by Ian Stokes and accentuated by a pubertal growth of 25 cm at the spine.

 Sensorimotor circuits have nonlinear properties. We note: - Thresholds, - time delays of proprioceptive feedback, - neuromuscular delays of force production. The nonlinear geometry of musculo-skeletal connections (e.g., the dependence of the moment arm of muscles upon joint angle) contributes to non-linear properties of the sensorimotor system. The system of posture control must deal with the two tasks simultaneously, one sets a distribution of tonic muscle activity (“posture attitude”) and the other is assigned to compensate for internal or external perturbations (“equilibrium”). The system constantly oscillates between anticipation and postural feedback. Postural stability requires constant activity of axial muscles to stabilize the trunk (and head) and to compensate for movements of the distal parts of the body, if necessary. Learning and physiotherapy aims at transforming retroactive postural corrections into anticipated postural corrections,

 The pyschological environment evolves with age in parallel with the motor function. The child is not a miniature adult. After a spatial exploratory phase, his initially imaginary environment will become integrated into reality. He will share his world with his friends of the same age. It is a sometimes a magical world populated by heroes. The beginning of puberty will put an end to this world and bring him closer to the world of the adults. This will be his world with social and cultural codes different from those of his parents. He will be autonomous with his powerful technology.

 In the Lyon Method, the corrective exercise will be performed with a stimulation of the postural system by slightly anticipating the physiological maturation and taking into account the environment. For example, for a scoliosis of 20° at the age of 11, we will insist on agility and coordination like wonderwoman.