Seated posture

The ability to relax at will is essential for occult work. All meditations should be preceded by relaxation. At first, it may take some time, but practice will increase your skill. Relaxation makes your body a clear channel, transparent to the in-flowing light, and so enabling energy to flow unimpeded. When seated in the meditation posture, focus first upon your feet. Tense the muscles of both feet for about four seconds, then allow them to relax. 

Atonic seizures are those in which the patient has sudden loss of postural tone. If standing, the patient falls suddenly to the floor and may be injured. If seated, the head and torso may suddenly drop forward. Although most often seen in children, this seizure type is not unusual in adults. Many patients with atonic seizures wear helmets to prevent head injury. 

The basal ganglia are part of what is referred to as the brain s extrapyra-midal system of motor control, so called to distinguish it from the pyramidal nerve tracts that control voluntary movement. The extrapyra-midal system is most directly associated with involuntary aspects of movement such as muscle tone and posture. However it has extensive connections with other parts of the brain, especially the frontal cortex, the seat of personality and rationality. This functional network... mediates volitional motor activity, saccadic eye movements, emotion, motivation, cognition and social behaviour (Wonodi, Hong, Thaker 2005, p. 340). Thus conditions that effect neurotransmission in the basal ganglia can be expected to have far-reaching functional consequences. 

Hsiao, H., and Keyserling, W. M., Evaluating Posture Behavior During Seated Tasks, International Journal of Industrial Ergonomics, Vol. 8, 1991, pp. 313-334. 

Even with an ergonomic chair, many people will have back pain if they sit continuously. The reason is that the disks of the back are nourished by movement of the back—no movement, no nourishment. Thus, encourage seating posture variability by having the person walk occasionally (to answer the phone, discuss things with others, take breaks). 

A critical consideration when selecting or designing a user interface is that the ability of the user to accurately control the interface is heavily dependent upon the stability of the user within the wheelchair. Often custom seating and postural support systems are required for a user interface to be truly effective. The placement of the user interface is also critical to its efficacy as a functional control device. 

Many people cannot use the wheelchairs as they come from the manufacturer. Specialized seating is required to help persons to remain in a comfortable and functional seated posture for activities that enable them to access work and attend educational and recreational activities. Orthotic supports, seating systems in wheelchairs, chairs that promote dynamic posture in the workplace, and chairs for the elderly that fit properly, are safe, and encourage movement all fit into the broad category of sitting technology. 

Ityury from Shock and Impact. Physiological responses to shocks and objects impacting the body include those discussed for whole-body vibration. For small contact areas, the injuries are often related to the elastic and tensile limits of tissue (Haut, 1993 von Gierke et al., 2002). The respcmses are critically dependent on the magnitude, direction, and time history of the acceleration and forces entering the body, the posture, and on the nature of any body supports or restraints (e.g., seat belt or helmet). 

Apparent Mass of Seated Persons. The apparent mass is often used to describe the response of the body at the point of stimulation rather than the mechanical impedance, and is the complex ratio between the dynamic force applied to the body and the acceleration at the interface where vibration enters the body. It is commonly expressed as a function of frequency, and is equal to the static weight of a subject in the limiting case of zero ftequency when Ae legs are supported to move in unison with the torso. The influence of posture, muscle tension, and stimulus magnitude on the... 

FIGURE 10.4 Effect of posture (N— normal E—erect B—with backrest), muscle tension (T— tensed muscles), and stimulus magnitude (0.25,0.5,1.0, and 2.0 m/s ) on the apparent mass of a seated person for four subjects (see text for explanation). (Fairley el at., 1989.)... 

Ill) Seating facilities In special decompression chambers shall be so arranged as to permit a normal sitting posture without cramping. Seating space, not less than 18 inches by 24 inches wide, shall be provided per occupant. 

Many jobs require performance of tasks in the seated position. Constant sitting in poorly designed chairs, in stressful postures, to carry out visual or manipulative tasks is a common source of recurrent or persistent back pain. Appropriate worlq)lace and chair design promote maintenance of correct posture and the prevention of postural strain. 

The keyboard should be detachable so that it can be positioned anywhere on the desktop and a correct posture adopted while working at the keyboard. The chair should be adjustable in height, stable and have an adjustable backrest. If the knees of the user are lower than the hips when seated, then a footrest should be provided. The surface of the desk should be nonreflecting and uncluttered. 

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