6 Theoretical Part – VM2G

View of Human Motion in Terms of

• Geometry
• Mechanics
• Biomechanics
• Anatomy
• Neurophysiology

“Only the type of certainty derived from the cooperation of mathematics and empiricism allows us to talk about science.” Professor Joseph Ratzinger
– Pope Benedict XVI

The aim of this chapter is to provide the view of the human locomotion from atypical standpoints. Current textbooks of biomechanics and anatomy describe the locomotion of the human body in the case of a fully-developed adult individual. I think, the fundamental principles of locomotion of the human body are based on the early developmental phase in the first year of life. This period is extremely intensive in many aspects. It is particularly essential for the future life and for building good fundamentals of locomotion that would become unchangeable in the older age.

For a deeper understanding, it is necessary to view the locomotion of the human body from the perspective of geometry followed by mechanics and, at the higher level, biomechanics. Anatomy then forms the basis of an even higher perspective. Finally, after passing through these stages it is possible to perceive movement regulation – i.e. the neurophysiology.

Fundamental Facts about the Geometry of Human Locomotion

• Supporting points, supporting lines and supporting surfaces
• Points of motion and their vectors
• Centre of gravity of the body, the head and the limbs
• Forces, chains of forces and their vectors

“God is a geometer and it is necessary to search the way from chaos to unravel the order.”
– Plato

Performance of any movement imposes necessary conditions of creating the points of support for the object and points that move together with the object. If we thought of the locomotive apparatus of the man from this point of view, we would also find the point that would serve as support and points that would serve as locomotion.

Similarly to physics, we can find the precondition of symmetry in the mechanics of the locomotion of the human body, too. Symmetry is important because it plays a significant role during the creation of stable systems with minimal concurrent energy requirements. Symmetry imposes many rigid restrictions, but on the other hand, it is extremely useful as it removes redundancies from the system.

Animation development of locomotion in the adult body

From a clinical point of view, deviations from symmetry lead to gradual decentralisation of joint surfaces, shifts in axial settings of the joints, blockages of the joints, herniations of, e.g., intervertebral discs and to degenerative changes due to incorrect load on joint cartilages.

Maintenance of joint symmetry in resting positions and in motion is the goal of autonomic regulation. From the outside, it is practically impossible to achieve the permanent recovery and normalisation of the symmetry itself by an analytical intervention. Symmetry completely depends on the complex system of regulation of muscle tone, regulation of righting and postural reflexes, autonomic regulation of the posture of the body and autonomic regulation of the basic stereotypical movements.

Symmetry as the fundamental precondition of locomotion enables muscular functional changes, “metamorphoses” within the system of stereotypical movements.

The general symmetry of the human body is extremely complex. It is provided by spirally organised muscular kinematic chains. There are two types of chain connections: right-to-left and left-to-right spiral chains. Concurrently, the chains are cranio-caudal and caudo-cranial. In terms of force mechanics and velocity, the chains could be divided into two types. Fast chains have a steep spiral. They are primarily intended to follow fast motion. The slow, power chains have shallow spirals and are intended for tensile exertion.

Animation development of locomotion in the adult body

Supporting Points, Supporting Lines and Supporting Surfaces

The development of motor skills is heading towards a gradual decrease in supporting surfaces down to supporting lines and supporting points.

A supporting surface is largest in a child after birth and it becomes even larger in the case of early developmental impairment. Concurrently, the centre of gravity is situated low in accordance with the width. This also applies conversely. The more the supporting surfaces diminish into supporting points, the higher and more labile the centre of gravity is situated.

Clinically, the enlargement of the supporting surface can be observed during the reaction of the reflex of Moro. The child abruptly extends both hands out to enlarge its supporting surface and the positional certainty that was disturbed by the stimulus.

Basically, there are two types of supporting surfaces: the stable ones with at least four supporting points and labile ones with three supporting points.

If the supporting surface were stable, the centre of gravity would be inside of this surface almost every time. Under normal circumstances, the stable surface can’t enable the locomotion of the body.

Three supporting points become a necessary precondition for movement. The elevation of the body’s centre of gravity and the limbs enables the points of motion to divert these centres of gravity from the supporting base. The centres of gravity have so far stayed inside the supporting surface. Hence, the body has been stable. The centres of gravity shift out of this inner space of support. The supporting surface diminishes to two supporting points, creating the supporting line. Bordered by two points, the supporting line is very labile. It allows the simple shift of the centres of gravity to a new position. This forms the basis of the movement.

The more the supporting base diminishes, the more the centre of gravity of the body is elevated into the space. This increases the overall lability of the body. Alternation of the stable and labile supporting bases is fundamental for the implementation of the movement. This alternation of supporting sectors is related to the phase shift of the centre of gravity within the space in terms of an increase in the lability of the centre of gravity against its stable position.

“Structurally”, this secures the ability of the body to offer to the centre of gravity compensation for its deviations. These deviations are also created at rest, but they are even more remarkable in motion. Their compensation is implemented in three basic spatial planes.

Points of Motion and Their Vectors

The situation concerning the compensations of the deviations from the centre of gravity becomes even more complex in motion. The deviations acquire an asymmetrical quality because the body is situated in the movement trajectory in three-dimensional space. During the compensation of the deviation, the kinetic energy of the axial organ and limbs, acceleration and deceleration of the movement of the very body, the extent of adhesion of the surface of support of the moving limb and many other factors must be “included”.

These complicated calculations of regulation of the equilibrium and maintenance of the symmetry of the motion happen naturally. It is possible to interfere with this action only marginally and for a short period. Only in individuals, who have undergone specific training, the ability of active interference with the course and regulation of the autonomic regulation of the movement could be observed, e.g., in ballerinas. This ability gradually diminishes after cessation of the training and the regulation falls under “the rule” of the autonomic programs.

During human motor development, the programs of automated stereotypical movements go through their genetically predetermined process. In the period of developing an upright stance, from birth to about 1.5 years of age, programs determined for the ability of the body to move in the environment with gravity are being “unpacked and loaded”.

The gravity wasn’t perceived by the child during the prenatal period. Thus, the program couldn’t be initiated.

Concurrently with the maturation of the basic righting, antigravity and balancing stereotypes, the basic stereotypical movements are initiated, e.g., stepping or grasping stereotypical movements. These antigravity programs and basic stereotypical movements mature with the body and are completed when full physical maturity is reached. Practically, the important autonomic programs of locomotion are completed concurrently with maturation of the physical constitution. In this period, and shortly afterwards, the best results in sports could be observed since the gross motor skills play the main role in the sport activities.

Video – New-born reflexes

Video – New-born reflexes

Middle age usually allows noncomplicated implementation of the motor programs and the musculoskeletal system. This relates to the necessary care of the next generation. If the programs were loaded inaccurately in the first year of life, the first severe impairments of the locomotive apparatus would start to appear.

Disturbances of the posture, righting, balancing and anti-gravity mechanisms and also related disturbances of the basic movement stereotypes formed and ossified. For example, intervertebral disc herniation is among the most common pathologies.

In later life, the disturbances of the locomotive apparatus related to premature degenerative processes of the joint cartilages start to play a part. They are also caused by the incorrect program regulation and subsequent erroneous physical growth. In all likelihood, these errors not only add on to each other, they in fact multiply each other. Due to the influence of its increasing entropy, the regulation of the locomotive apparatus generally degenerates. It is manifested at the level of increasingly inaccurate regulation and in progression of the degenerative processes of the joint cartilages, decrease in density of the bone matrix, reduction of elasticity of ligaments and joint capsules and atrophy and shortening of the muscular mass. These biomechanically unfavourable parameters constitute the common cause of falls and subsequent bone fractures and other serious injuries among the elderly.

The Centre of Gravity of the Body, the Head and the Limbs

Kinematic Mechanism

Kinematic mechanism represents another view of the function of the musculoskeletal apparatus of the human body. It’s extremely complex. Perhaps, it’s the most complex moving phenomenon on earth in terms of kinematics. The complexity is not an end in itself. It originates in the purpose, to which this mechanism has been “constructed”. Unlike various unhuman apparatuses for locomotion, the human body has been equipped with abilities of extraordinarily variable activities. The setting of fine motor skills is utterly unique. The essence of the excellent variability and faculty of fine motor skills of the hand and orofacial region consists of extremely complex regulation programs. Their growth and “program installation” takes a very long time, from a year to a year and a half. Due to this complexity and long complicated “installation”, the programs are concurrently very fragile and prone to damage. The damage could occur in utero, during delivery and during the whole development, i.e. up to a year and a half.

Muscular Forces, Chains of Forces and Their Vectors

Muscular forces generated by the locomotive apparatus, the way they’re still comprehended, would not allow the performance of basic locomotion or more complex kinetic functions. Normal motor development in the first year would not go through its milestones – the turning, the belly-crawling, the crawling on all fours and the standing upright.

The current view of the executive organ of motor force, i.e., the muscle, is quite reductive and compares its function to that of a piston in a rod. It only enables pulling in one direction or relaxation of the pulling in the opposite direction. This one-dimensional image of muscular function constitutes the basics for the examination of muscular strength according to muscular tests. Muscle functions are comprehended in isolation and analytically. The muscles are described anatomically by their beginnings and insertions, while the beginnings of the muscles had their paths decidedly set on the torso.

In this analytical model, the resulting movement the muscle can perform is planar. Thus, it is how the muscle is examined during the muscle test. This simplified image is further implicated into the practical approach to the musculoskeletal apparatus in training or rehabilitative care.

Muscular Chains of Forces and Their Vectors

To perform basic stereotypical movements and the “overlying” complex kinetic creations, the human locomotive apparatus needs much more complex force mechanisms. One-dimensional muscular levers wouldn’t be able to move it. The kinematic mechanism of the locomotive apparatus is “powered” by a complex and extremely spatially-complicated set of force vectors. The effective mechanisms that generate these force vectors are muscular chains. Because of their extraordinary complexity, and because they haven’t complied with the established analytical anatomy of the locomotive apparatus, their existing description is quite imperfect.

Muscular chains wrap the skeleton in spiral loops and run inside through it. The loops cross each other on multiple levels. Muscular chains are significantly functionally and anatomically interconnected. (Myers 2014) 1

Force vectors generated by muscular loops are very complex and they exhibit spatial spiral trajectories. The system is extremely complicated and the possibility to measure it through a muscle test or similar tools is totally impossible.

Functional connections of muscular chains take place as soon as the intrauterine developmental period (Langmeier, 2006).1 Muscular chains responsible for the connection of basic antigravity and righting functions, and the functions of the basic stereotypical movements spring into action during the first year of life after birth. Interventions within this motor and neurophysiological maturation are highly undesirable, except in cases of necessary therapeutic interventions due to the necessary repair of the impaired motor development.

2D – Functional Anatomy

The existing view of the locomotive apparatus is strongly reductionist. It is based on an anatomical view that originated in the 16th century in accordance with the descriptions of the anatomist A. Vesalius. This concept is only two-dimensional. It was useful for practical surgical and later orthopaedic interventions into the musculoskeletal apparatus. It was utterly sufficient for these purposes and the reduction of the muscular activity to a formula: origin + insertion = function wasn’t detrimental.

Gradual increase in demands on the locomotive apparatus, for example, widening and intensification of sport activities, forces more training and methodological approaches. They ought to improve the general condition and the kinetic abilities. They are also related to therapeutic interventions on the overloaded and overtly worn-out and increasingly injured musculoskeletal apparatus. Thus, all these training rules and methods, performance or leisure sport activities, fitness and the subsequent therapeutic intervention on the musculoskeletal apparatus are based on a 2D anatomical concept, which is remarkably simplified, analytical in nature and intended for completely different “treatment” with the musculoskeletal apparatus.

These anatomical basics can’t be useful for other requirements. Other specialties have also been evolving on this 2D anatomical model: biomechanics, kinesiology, sports medicine, etc. The limited view of the 2D anatomy is being expressed by an increase in, and multiplication of, this essential “error” in several scientific specialties and the methodologies of sport trainings etc.

The motion of the limbs and the axial organ that originate within such a system could only be planar. The didactic crutch that represents the anatomical planes of the body, has further narrowed or even closed the perception. Individual muscles and muscle groups were given the functions that are based on the autopsy description of the corpse. This also corresponds to the topography of the body and the muscles of a standing or lying figure of an adult individual with palms turned forward. Regulation of this simplified system is practically reduced to regulation of individual muscles and muscle groups.

3D – Functional Anatomy

A functional 3D anatomical model is based on the observations of the real muscular functions. Muscle function is determined by the actual movement that is being performed by the musculoskeletal apparatus. Searching for the muscle function through its origin and insertion is secondary regarding the working of the musculoskeletal apparatus. Muscle functions are extremely variable and completely depend on their involvement within the muscular kinematic chains. The muscles are only the effector organs of the brain motor cortex. Their function constitutes the primary expression of the motor regulation by the CNS.

It is only necessary to look for the muscular functions in the actual movement in which the muscles participate. The locomotion of the musculoskeletal system is always global. It is based on the biomechanical principles. They are the only clue for the determination of the actual muscle function relevant for the current moment. Every next moment within the course of the movement that shifts the whole centre of gravity of the body and the limbs fundamentally affects the new and further changing functions of the muscles.

The attempt to describe the muscular functions on an “immobilised” torso or the limbs on the contrary results in a totally misleading image. Under physiological kinetic conditions, muscular function is “fluidised” and always changing. The real muscular function could be seen only in context with actual points of support and motion. In every moment, the supporting points show the direction of the “origin” of the muscle, from which the movement initiates. On the other hand, in each moment, the points of motion constitute the direction in which the muscle “inserts”. These “origins and insertions” continuously change during the course of the movement. If it wasn’t so, man wouldn’t be able to move within the 3D space at all. Movement, which has been trapped in a descriptive flat 2D anatomy, is totally non-physiological.

The action of the functional 3D kinematics can be well demonstrated on the locomotion of the limbless body.

Spiral muscular loops work like springs that are concurrently being pulled tight in opposite directions. In terms of mechanics, there are compression and tension types of springs. They provide the propulsion to the swinging kinematics of the locomotive apparatus of the human body. The very swinging kinematics is spatially oriented so that the centre of gravity of the body, the limbs and the head copy the spatial curves. These curves get close to the ideal only if they are sinusoidal in shape.

In terms of the influence on the very biomechanical construction of the musculoskeletal apparatus, movement through 2D trajectories is harmful. It doesn’t respect the essential rules of the function of the human locomotion.

video

video

General Biomechanics of the Locomotion of the Human Body

Musculoskeletal Apparatus in 3D Space – Spatial Course of the Movement

The musculoskeletal apparatus of the human body organised into the 3D spatial system becomes the fundamental precondition for the course of locomotion in 3D space. Vojta repeated very often, that the “posture follows the motion like a shadow”. Spatial organisation of the bodily system should enable a course of movement that would always contain all three spatial motion vectors and would more or less approach the ideal symmetrical spiral trajectory in its course.

Biomechanical Construction of the Musculoskeletal Apparatus and the Spiral Dynamics of the Vectors of Motion

Clinical observation performed by V. Vojta allowed him to describe the muscular chains, which are responsible for the locomotion of the body. He classified them as straight or oblique chains and described their function in detail within the motor development from the birth to the unaided gait, in terms of both physiological and pathological course of development. The very courses of individual muscles indicate that the biomechanical construction of the musculoskeletal apparatus is built with regards to the combination of two components – the force and the velocity.

Basically, the system can be classified so that the force components of motion are situated rather medially on the axial organ, and rather proximally on the limbs (on the shoulder and hip girdles). Again, components responsible for the velocity are located rather laterally predominantly on the axial organ and distally in the limbs.

Combining the force and velocity components of locomotion, the musculoskeletal apparatus reaches the highest possible efficacy for which it’s been constructed. It’s capable of fast movements, predominantly on the limbs, as well as strong movements, predominantly on the torso. Of course, it also performs a wide range of exact and adjusted movements within the fine motor skills of the hand and in the orofacial region.

It turns out that the course of individual muscles, muscle groups and muscle chains is curved into a spiral. According to the steepness or the shallowness of each spiral it could be distinguished by whether it was determined for the creation of predominantly fast movement or predominantly strong movement, respectively. The spirals of great steepness have been constructed for fast movements with a great degree of acceleration but small degree of force. The spirals of shallow course have been projected for slow movement with a slow degree of acceleration, but they possess the capacity to escalate the force involved.

“Different muscles and muscle groups group together during all more complex movements into functional units – the functional chains are called muscular loops. These loops could generate a completely different motor expression that would correspond to contractions of each individual muscle contained within the respective loop. A kinematic chain is specific for each movement and changes even during more complex kinematic sequence. According to the ending of the chain, we recognise open kinematic chains. (The last link is free and doesn’t contain a loop) or closed kinematic chains. (There is no free ending.)” (Kovařík and Langer, 1994)1

The implementation of muscular loop takes place in any position.

Muscle spirals wrap around both the axial organ and the limbs so that they rotate spirally around the medial axes. In the axial organ, they are formed by the ribcage, spine and pelvis; in limbs, they are formed by the long bones. The spirals describe curves in the right-to-left and left-to right directions. Forced expiration of the chest or clenching of the hand into the fist could stand for an example of concurrent “tightening” of the right-to-left and the left-to-right spiral.

Balanced regulation of the spiral locomotion is what enables the musculoskeletal apparatus to essentially move the body and all other extension motor formations. Permanent centration of all joints of the musculoskeletal apparatus, i.e. both the peripheral, bearing and spinal joints, is mediated by the spiral locomotion. The impairment of the regulation of the spiral muscular coordination leads to joint dislocations including the pathological shifts of intervertebral discs or knee menisci.

Performance of the movement via spiral trajectories is highly economical and safe for the locomotive apparatus. Spiral trajectory occurs in all types of movements, and each stereotypical movement and its components are implemented through it. Spiral trajectory that approaches the physiological ideal approaches the rotatory ideal as well. The greater the deviation of the trajectory is from the physiological ideal, the greater the deviation is from its rotatory shape.

Deviated and pathological kinetic trajectories significantly increase the economical demands on the movement. The degree of the skeletal motor components’ wear increases. Fatigue increases along with a concomitant decrease in the performance of the locomotive apparatus at all levels.

The Basic Preconditions for the Performance of the Normal Stereotypical Movement – Coordinated Contractionary Waves

To perform any stereotypical movement in an ideal way, all muscular chains must necessarily contribute to the coordinated contractionary wave.

The regulation of the muscular coordination in the contractionary waves takes place according to a predefined algorithm. To perform the correct coordinated movement, it is necessary to provide ideal biomechanical conditions.

The course of the stereotypical movement in the contractionary waves of the muscular chains utilises all types of muscular contractions, i.e. the isometric, dynamic (formerly known as isotonic), eccentric and concentric contractions.

The result of the activity of the coordinated contractionary waves in the muscular chains

The current view of the muscular kinematic chains or muscular loop originates from the conception of the classical descriptive anatomy, i.e. the 2D view. Therefore, the chains and loops are only thought about and depicted in the planar sense.

Foundations of the Developmental Biomechanics of the Locomotion of the Human Body

Functional Description

For easier characterisation and simpler illustration of the developmental biomechanics, we borrow the terminology of general mechanics of the machines. In terms of function, the musculoskeletal apparatus of the human body represents a specific form of an extremely complex mechanical system.

The axial organ of the body itself could be divided into the pelvic girdle and the thoracic girdle with scapulae. We will call the pelvic girdle “the lower differential” and the thoracic girdle with scapulae “upper differential”.

Both differentials, unlike those commonly used, e.g., automobile differentials, are triaxial.

Unlike the classical differentials that have been constructed for transmission of the torsion momentum, the triaxial differentials of the motor apparatus of the human body have only been adapted for the transmission of momentums from swinging motion. These momentums are transmitted to forces of the levers of the limbs.

The lower pelvic differential transmits the swinging momentum directly to the lower limbs. This differential is a firm pelvic girdle and the connection with the lower limbs is secured by the robust musculature. Hip joints have been constructed as bearing joints with a limited range of motion.

Compared to the lower one, the upper differential is significantly more complex due to scapulae that represent in a certain sense “inserted” bones. Together with claviculae, they constitute the foundations for two functionally and anatomically separate arm girdles. Concurrently, the bony base of the ribcage of this differential is more elastic than the pelvic bone girdle. The function of the upper differential, except the transmission of the swinging momentums to the upper limbs, is to ensure the functions of breathing mechanics and to carry the head. In terms of mechanics, the head could be viewed as a counterweight.

Connection and the transmission of the forces between both differentials is primarily enabled by the lumbar vertebrae L1 – L5, including the discs. In terms of general mechanics, they are the “cardan joints”, which are, however, triaxial ones, too. Their function involves the transmission of the swinging force momentums between the upper and lower differential. Besides the mutual transmission of the forces between both differentials, these cardan joints indirectly contribute to the force transmission on the upper and lower limbs.

The Limbs – The Transmission Levers

In terms of general mechanics, the limbs could be considered the “transmission and efficient levers” of the system of the musculoskeletal apparatus of the human body. Their goal is to highlight the functional efficiency of the kinematic system.

The transmission levers significantly increase the efficiency of the whole musculoskeletal system of the human body, particularly the variability and efficiency of all motor skills.

Head as the Counterweight

Again, in terms of general mechanics, the function of the head can be viewed as the counterweight suspended on the triaxial cardan joints, i.e., on seven cervical vertebrae. The mechanical role of the counterweight is helping to counterbalance the highly placed centre of gravity of the body during the upright bipedal gait.

Biomechanical Construction of the Musculoskeletal Apparatus and Its Interlinking

Current analytical conception of the musculoskeletal apparatus is suitable for the didactical purpose of the descriptive anatomy than for the real functional view. The description of individual parts of the body divided to the head, thorax with spine, pelvis, upper and lower limbs creates the generally mistaken illusion of some practically independent and loosely interconnected parts of the body.

The reality is shown to be different. The musculoskeletal apparatus can work only as a whole. Individual parts are completely intrinsically bound or rather chained in the structurally anatomical and, particularly, functional meaning. For easier understanding, the view of the body could be comprehended as multiple interconnected kinematic chains. These chains could be further classified as closed and opened ones.

The very kinematics of the interlinking of the musculoskeletal apparatus is very complex as it is intrinsically linked to the 3D anatomical model of the musculoskeletal apparatus. It exhibits a large amount of freedom within the kinematic vectors.