Human position
From Wikipedia, the free encyclopedia
Human position refers to a position of a human body. It can also be called a person's attitude or bearing.
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[edit] Basic human positions
While not moving, a human can be in one of the following main positions.
[edit] Standing
Although quiet standing appears to be static, modern instrumentation shows it to be a process of rocking from the ankle in the sagittal plane. Standing posture is often likened to an inverted pyramid. [1]
Standing posture relies on dynamic rather than static balance. Our Center of Mass (COM) is in front of the ankle. A static pose would cause us to keel over on our face. In addition, we are constantly subjected to external perturbations such as breeze and internal perturbations from respiration. Erect posture requires adjustment and correction. Traditionally our correction was explained by the spring action of our muscles. This is a local mechanism that takes place without the intervention of the Central Nervous System (CNS). Recent studies, however, show that spring action by itself is insufficient to prevent a forward fall. Also, human sway is too complicated for spring action to be the sole mechanism. [2]
According to current theory, the CNS continually monitors our direction and velocity below our conscious awareness. Our vertical body axis alternates between forward and backwards tilts. Before each tilt reaches the tipover point the CNS counters with a signal to reverse direction. Sway also occurs in the hip and there is a slight winding and unwinding of the lower back.[3] [4]
An analogy would be a ball that is volleyed back and forth between two players and is not allowed to touch the ground. The muscle exertion required to maintain an aligned standing posture is crucial but minimal. A little goes a long way. Electromyography has detected slight activity in the muscles of the calves, hips and lower back. [5]
Although the pendulum model is a good approximation, a time series of postural sway shows much more variation than is seen in a physical pendulum. In the past the variation was attributed to random effects[6]. A more recent interpretation is that sway has a fractal structure[7][8]. A fractal pattern consists of a motif repeated at varying levels of magnification. The levels are related by a ratio called the fractal dimension. It is believed that the fractal pattern offers a range of fine and gross control tuning. Fractal dimension is altered in some motor dysfunctions[9].
Lately, attention has focused on the role of the core muscles in maintaining stability. The core muscles are deep muscle layers that lay close to the spine and provide structural support. The transverse abdominals wrap around the spine and function as a compression corset. The multifidi are intersegmental muscles. Dysfunction in the core mucles has been implicated in back pain.[10][11]
[edit] Sitting
Sitting requires a more or less horizontal structure, e.g. a chair or the ground; special ways of sitting are with the legs horizontal, and in an inclined seat; while on a chair the shins are usually vertical, on the ground the shins may be crossed in the lotus position or go horizontally underneath the thigh in a seiza.
[edit] Supine
Lying horizontal, face up. Toes up
[edit] Prone
Lying horizontally, facing down..
[edit] Optimal human positions and balanced erect posture
Posture is the emergent alignment of the body that remains relatively constant in its underlying structure and unity across various forms of human positions. It refers to the unconscious and stable structural disposition of the body framework attained over a long period of continuous body movements and patterns.
These stable postures attained over time is a result of one's lifestyle and orientation. Over time people come to attain an average posture, bad or inefficient posture, and sometimes a good or effective posture. The quality or effectiveness of posture is related to the proportionate structure of the body framework and the optimal balance of the body.
A bad posture or slouching posture is unable to optimally distribute weight across the body framework, and hence is ineffective. An average posture is able to maintain distribution of weight and form but does not attain optimal form and maintenance. A good posture or an erect posture is able to completely and optimally attain balance and proportion of the body mass and framework. A well proportioned erect posture optimizes breathing and affects the circulation of bodily fluids. An erect posture is therefore most desirable and highly effective for the body structure and proportion.
An erect posture or well-proportioned posture involves various elements of the body and its co-ordination. It includes optimally unfurling the spine until the lower back curves inside while holding the chest raised high without straining breathing. The head assumes an optimal position while keeping the chin parallel to the ground. In an erect posture, the shoulders are very straight and pulled back. This acts like the yardarm (horizontal spar on the mast of a ship). Hence while bending, even though the spine would curve, the posture still remains erect because the shoulders remain straight and pulled back maintaining the body proportion and balance. The optimal structural alignment of the body leads to a straight back. This structural alignment consolidates over a long span of time leading to a well balanced posture that becomes a natural disposition.
In posturology, posture is elaboration and active preservation of the configuration of the various segments of the body in the space; it expresses the way body faces the stimulation of the outside world and gets ready to react to it.
The configuration of the various segments of the body in space is elaborated on a mode rather phasic but not exclusively, it is maintained on a rather tonic mode but not exclusively.
[edit] Human positions and posture in society
A well balanced or erect posture is considered as an integral part of physical attractiveness. In most cultures an erect posture is considered as a mark of a well balanced and adaptable personality. Young boys and men are expected to have erect postures. Military regimentation and several boarding schools enforce regimen on young people to have an erect posture, the consequence often being what is termed a military posture or over-correct posture which may be considered excessively erect with poor balance resulting from excessive tension in the back muscles. Women consider erect posture as one of the most salient features of attractiveness in men.[citation needed] This appeal for erectness also makes women have erect postures themselves. It is also observed that significantly more women have erect postures than men. Other communities stress posture as an integral part of their lifestyle. The Nuba people in Africa are also famed for their posture, which is a product of their natural lifestyle. Their beauty was documented by the Motion Picture director Leni Riefenstahl. Across societies, various stylizations of human positions and postures are set for specific occasions, which include etiquette and ceremonial conducts.
[edit] See also
- Alexander Technique
- Dance position
- Ergonomics
- Fetal position
- Kohnstamm's phenomenon
- Lodging
- Mitzvah Technique
- Motor control
- Positional asphyxia
- Postural Integration
- Yoga
- Terrestrial locomotion in animals
