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PubMed1989

The effect of head posture on muscle contact position: the sliding cranium theory.

The effect of head posture on initial occlusive contacts has been studied extensively by researchers in the basic sciences, dentistry, and physical medicine. The purpose of this paper is to review their theories and propose a new mechanism that attributes the effect of head posture to a change in the upper to lower jaw relationship. This mechanism is referred to as the sliding cranium theory. To understand how head posture alters initial tooth contact or muscle contact position, the arthrokinematics of the occipital-atlantal joint are covered in detail. The implication of the proposed new theory have relevance for dentists concerned with occlusal function and the treatment of temporomandibular joint dysfunction with temporomandibular repositioning, as well as for physical therapists who effect a change in head posture through mobilization procedures and therapeutic exercise. To conceptualize the proposed theory two easily performed tests are described. The sliding cranium theory presents a mechanical model that explains the interrelationship between the head-neck complex and the craniomandibular system in a way that has not been previously done.

Atlanto-Occipital Joint↗
PubMed1990

Study of sitting posture variations using the nose and mandible as reference points.

The purpose of this study was to examine the average sitting posture in normals and to determine how clinically observed sitting posture varies as a function of the duration of relaxed sitting, patient awareness of being observed, and other situational factors. The head, neck, and upper thorax of five naive patients demonstrated increasingly anterior and inferior displacement during five minutes of relaxed sitting. These postural alternations were instantaneously reversed when the subjects were made aware that they were being observed. We conclude that sitting posture must be assessed in relationship to the patient's length of time sitting, awareness of being observed, level of instruction on how to sit, and chair style.

Adult↗
PubMed1998

Observations on the correlation between posture and jaw position: a pilot study.

The aim of this pilot study was twofold. The first was to show a method for having an objective and dynamic analysis of body posture, evaluating weight distribution and its connections with different mandibular positions. The second was to verify if a neuromuscularly stimulated occlusal position, called myocentric occlusal position, is associated with a positive or negative postural charge. For the second aim a group of 20 subjects (including both males and females), was chosen. Posture of each subject was analyzed in three different conditions: centric occlusion, rest position and myocentric position. To evaluate the dynamic of posture a platform capable of measuring the weight on the feet supporting points and the related variations during time of observation and the swinging of body barycenter was used. The data showed that there is an improvement in the position of the barycenter from the centric occlusion to the myocentric position. Such an improvement can't be observed from the intercuspal position to the rest position. The results of this pilot study are discussed.

Adult↗
PubMed2000

The influence of forward head posture on dental occlusion.

A well established premise in the field of craniomandibular and cervical spine orthopedics is that forward head posture (FHP) adversely affects mandibular position and therefore dental occlusion. The purpose of this study was to investigate the influence of FHP on the initial occlusal contact pattern (IOCP) in order to provide further clarification on this important topic. Thirty-nine healthy subjects, 10-74 years old, underwent a series of tests in which the IOCP was recorded in four different head positions using the T-Scan Occlusal Diagnostic System. Three tests each were performed in military posture (MP), natural sitting posture (NP), FHP, and maximal forward head posture (MFHP) for a total of twelve trials. A repeated measures analysis of variance failed to demonstrate a correlation between FHP and IOCP; however, a multiple linear regression analysis revealed a relationship between age and the IOCP. This study raises questions about the relationship between FHP and occlusion.

Adolescent↗
PubMed2004

Using immersive technology for postural research and rehabilitation.

Posture has traditionally been examined by isolating individual control pathways to determine their specific contributions. However, if these pathways are responsive to functional contexts, then their responses may differ when the system is receiving simultaneous inputs from multiple pathways. Thus, we may never fully understand how the central nervous system (CNS) organizes behaviors in the real world from studies conducted in the minimized environment of the laboratory. The consequence of this is that when findings from the laboratory are applied to therapeutic intervention, the intervention may not be appropriate for all circumstances and will not fully meet the needs of the patient. We have united an immersive dynamic virtual environment with motion of a posture platform to record the biomechanical and physiological responses to combined visual, vestibular, and proprioceptive inputs. The virtual environment possesses content, contrast, and texture so that we can examine postural responses as they might occur in a complex, real-world environment. In this paper we specifically describe the factors guiding our choices of virtual technology and present data from young adults, elderly adults, and an individual with bilateral labyrinthine loss to demonstrate how multimodal inputs influence their postural response organization. Significant implications for future experimental and rehabilitation protocols are also discussed.

Adult↗
PubMed1998

Two-Dimensional Automatic Control Modeling of a Posture Control System.

A posture control model has been developed on the basis of the 2-dimensional feedback control theory. Human postural characteristics were investigated in 5 healthy participants. Tests were performed with eyes open and eyes closed. After 5 s of quiet standing, each participant was unexpectedly pulled forward by 30 mm at his pelvis height and then released. Postural sway was measured over 20 s at a rate of 100 per second. Transfer functions to represent the posture control characteristic were identified by the least squares' method. These showed good results of the model's fitness, predictability, and stability. The response of the eyes-closed condition to perturbation is more oscillatory than that of the eyes-open condition. It seems that the model identified could be applicable to ergonomics, sports, or clinical situations.

model fitness↗
PubMed2000

Maintenance operations: workstation adjustment, working posture, and workers' perceptions.

In the study maintenance workers were involved in pneumatic wrenching, oxy-gas cutting, and grinding at 5 different heights. Working posture and workers' perceptions were measured. Guidelines on working height were formulated in order to minimize the load on the musculoskeletal system. Data from the present experiment as well as from literature were studied in depth in order to disclose generic mechanisms behind the adoption of working postures during visual-manual operations in relation to workstation adjustment. It was found, for instance, that the working posture was constrained by a strictly followed relationship between gaze inclination and head inclination for-/backwards. Also, the study provided insight into the role of visual interference, viewing distance, manipulation distance, hand grip of the tool, and body support for stability. Concerning evaluation criteria for working postures, it was concluded that neck flexion/extension (i.e., head inclination for-/backwards versus trunk inclination for-/backwards) seems to be the dominant determinant of neck load, as compared to head inclination for-/backwards. Furthermore, the position of the upper arm with respect to the trunk, that is, shoulder flexion/retroflexion in particular, seemed to be a dominant determinant of shoulder and shoulder girdle load, as compared to upper arm elevation.

Adult↗
PubMed2003

Examining RULA's postural scoring system with selected physiological and psychophysiological measures.

The Rapid Upper Limb Assessment (RULA) survey is a posture-sampling tool used specifically to examine the level of risk associated with upper limb disorders of individual workers. This paper examines the relationship between RULA's postural scoring system and measures of surface electromyography (EMG), self-reports of discomfort, and job attitude questionnaires. Twenty participants each performed a 30-min typing task on a computer in 3 working postures based on RULA's scoring system. A statistically significant difference was found only in perceived discomfort. The perceived discomfort results demonstrated that RULA was able to identify "high risk" postures. The next question we need to ask is, does perceived discomfort result in tissue damage, or does tissue damage yield discomfort?

Adult↗
PubMed2005

Differences in dentists' working postures when adopting proprioceptive derivation vs. conventional concept.

New technologies and changes in dental care, including the proprioceptive derivation (Pd) concept, aimed at providing dentists with greater comfort and better health, were introduced in Thailand. The aim of this study was to investigate the differences in dentists' working postures when adopting different work concepts: Pd and the conventional concept. The results showed differences in dentists' sitting posture, clock-related working positions, and Rapid Upper Limb Assessment (RULA) scores. This implied that Pd helped dentists to discover new ways of positioning themselves, and working comfortably and effectively, which made it possible for them to adopt better working posture and have lower RULA scores. In conclusion, the Pd concept had a positive effect on dentists' working posture.

Adaptation, Physiological↗
PubMedDate not supplied

Improved ambulation and speech production in an adolescent post-traumatic brain injury through a therapeutic intervention to increase postural control.

PURPOSE: This case study examined the effectiveness of a programme designed to improve anticipatory postural control in an adolescent over years 2 and 3 post-traumatic brain injury (TBI). It was hypothesized that her difficulty in walking and talking simultaneously was caused by excessive co-activation of extremity, trunk, and oral musculature during upright activities. METHODS: The participant was treated weekly by physical and speech therapy. Treatment focussed on improving anticipatory postural control during gross motor activities in conjunction with oral-motor function. RESULTS: Initially, the participant walked using a walker at a speed of 23 cm s(-1). Two years later, she could walk without a device at 53 cm s(-1). Initial laryngoscopic examination showed minimal movement of the velum or pharyngeal walls; full movement was present after treatment. The measure of intelligibility improved from no single word intelligible utterances to 85% intelligible utterances after 2 years. DISCUSSION: The results suggest that less compensatory rigidification of oral musculature was needed to maintain an upright position against gravity as postural control improved. CONCLUSION: An adolescent 1-year post-TBI was followed as she underwent additional rehabilitation focussed on improving anticipatory postural control. The functional goal of simultaneously talking while walking was achieved through this intervention.

Accidents, Traffic↗
PubMedDate not supplied

The effect of hyperbaric oxygen treatment on postural stability and gait of a brain injured patient: single case study.

Hyperbaric oxygen (HBO) therapy has been found to reduce intracranial and cerebrospinal fluid pressures, and increase grey matter metabolic activity in patients with brain injuries. To date, few studies have quantitatively assessed the changes in the patient's functional outcomes following this expensive therapeutic intervention. The purpose of this case study was to examine the immediate and longer term changes in postural stability and gait in a 17 year old patient who sustained a traumatic brain injury, following administration of hyperbaric oxygen (HBO) therapy combined with physical and occupational therapy. The patient underwent assessments of postural stability and gait 1 week prior to HBO therapy, immediately following, and 6 weeks after completion of HBO therapy. Some improvements in postural stability were observed immediately following HBO, although these improvements were not evident 6 weeks later. Only slight improvements were noted in his walking abilities immediately following the intervention, with essentially little change evident 6 weeks later. The results of this do not support anecdotal evidence that there were substantial improvements in the subject's postural stability and gait following HBO therapy.

Adolescent↗
PubMed1983

Working posture and musculoskeletal problems of video display terminal operators--review and reappraisal.

In order to minimize the stresses on the musculoskeletal system, attempts have been made to develop design guidelines for video display terminal workstations. Evaluations of VDT workstations reveal that many of the health problems experienced by operators might be attributed to awkward postures caused by lack of consideration of these guidelines. In other cases, it may be a matter of specific individuals not fitting "average" workstations. This has led to an increasing emphasis on designing adjustable workstations which can be adapted to the individual worker's needs. Even when guidelines are followed and workstations are adjusted to fit individuals, a variety of postural complaints may arise. One of the most important contributing factors is the constraint which is typically placed on the posture of the VDT operator. Many tasks lead to prolonged static positioning of the back, neck, arms and legs; producing rapid fatigue and increasing the risk of chronic problems. Another factor which must be considered is the effect of repetitive motion patterns which could lead to disorders in the muscles, tendons, nerves and joints. Finally, the effects of job pressures must not be overlooked as a potential contributing factor in postural complaints.

Bone Diseases↗
PubMed2006

Influence of seat geometry and seating posture on NIC(max) long-term AIS 1 neck injury predictability.

OBJECTIVE: Validated injury criteria are essential when developing restraints for AIS 1 neck injuries, which should protect occupants in a variety of crash situations. Such criteria have been proposed and attempts have been made to validate or disprove these. However, no criterion has yet been fully validated. The objective of this study is to evaluate the influence of seat geometry and seating posture on the NIC(max) long-term AIS 1 neck injury predictability by making parameter analyses on reconstructed real-life rear-end crashes with known injury outcomes. METHODS: Mathematical models of the BioRID II and three car seats were used to reconstruct 79 rear-end crashes involving 110 occupants with known injury outcomes. Correlations between the NIC(max) values and the duration of AIS 1 neck injuries were evaluated for variations in seat geometry and seating posture. Sensitivities, specificities, positive predictive values, and negative predictive values were also calculated to evaluate the NIC(max) predictability. RESULTS: Correlations between the NIC(max) values and the duration of AIS 1 neck injuries were found and these relations were used to establish injury risk curves for variations in seat geometry and seating posture. Sensitivities, specificities, positive predictive values, and negative predictive values showed that the NIC(max) predicts long-term AIS 1 neck injuries also for variations in seat geometry and seating postures. CONCLUSION: The NIC(max) can be used to predict long-term AIS 1 neck injuries.

Accidents, Traffic↗
PubMed2007

Effect of aviation snip design and task height on upper extremity muscular activity and wrist posture.

Hand tools described as ergonomic in design are intended to reduce exposure to physical risk factors associated with work-related musculoskeletal disorders. Additionally, using the right tool for the job is believed to reduce exposure and, consequently, risk of disease. Sheet metal workers frequently use a cutting tool called aviation snips when fabricating and installing ductwork. The purpose of this laboratory simulation study was to determine the effect of (1) aviation snip design; and (2) work height on muscle activity, wrist posture, and user satisfaction among sheet metal workers. We hypothesized that specific aviation snips designs would be most appropriate for use at specific heights. Twenty-three sheet metal workers used three different designs of aviation snips to make curved cuts in sheet metal placed both at waist height and shoulder height. Conventional circular snips, straight snips, and an alternate design of offset snips were used. Upper extremity muscle activity was measured with surface electromyography, wrist posture was measured with electrogoniometry, and user satisfaction was rated by the participants on a survey. Statistically significant effects of snip design and task height on muscle activity, wrist posture, and user satisfaction were observed. However, no snip was preferable for all dependent variables. Work height had a greater effect on muscle activity and wrist posture than snip design. Field studies are indicated to determine the long-term effect of snip design on physical risk factors and risk of musculoskeletal disorders.

Adult↗
PubMed2004

Investigation of cerebral haemodynamics by near-infrared spectroscopy in young healthy volunteers reveals posture-dependent spontaneous oscillations.

Autonomic reflexes enable the cardiovascular system to respond to gravitational displacement of blood during changes in posture. Spontaneous oscillations present in the cerebral and systemic circulation of healthy subjects have demonstrated a regulatory role. This study assessed the dynamic responses of the cerebral and systemic circulation upon standing up and the posture dependence of spontaneous oscillations. In ten young healthy volunteers, blood pressure and cerebral haemodynamics were continuously monitored non-invasively using the Portapres and near-infrared spectroscopy (NIRS), respectively. Oscillatory changes in the cerebral NIRS signals and the diastolic blood pressure (DBP) signal have been identified by the fast Fourier analysis. Blood pressure increased during standing and returned to basal level when volunteers sat on a chair. The mean value of cerebral tissue oxygen index (TOI) as measured by NIRS did not demonstrate any significant changes. Oscillatory changes in DBP, oxyhaemoglobin concentration [O2Hb] and TOI showed a significant increase when subjects were standing. Investigation of the low frequency component (approximately 0.1 Hz) of these fluctuations revealed posture dependence associated with activation of autonomic reflexes. Systemic and cerebral changes appeared to preserve adequate blood flow and cerebral perfusion during standing in healthy volunteers. Oscillatory changes in [O2Hb] and TOI, which may be related to the degree of cerebral sympathetic stimulation, are posture dependent in healthy subjects.

Adolescent↗
PubMed2005

Development of a quantitative assessment system for correlation analysis of footprint parameters to postural control in children.

It is known that neurological impairments impact postural stability, but few studies have observed the biomechanical influence of foot structure on balance. The aim of this study was to develop an integrated device for investigating the relationship between static balance and the foot structure, derived from a footprint image, under clinical tests of sensory interactions. Quantitative analysis of the footprint image acquired during balanced standing was developed as an indirect measure of the longitudinal arch, an important structural component of the foot. A data pool was collected from 64 children, 32 children from each of two age groups (4-5 years old versus 8-10 years old). Six common footprint parameters derived from the footprint angle or contact area were used to investigate the relationship between footprint parameters and postural stability. Postural balance ability was evaluated by analyzing sway area in posturography under visual or somatosensory confliction conditions. The footprint parameters, derived from the footprint image, inter-correlated well with each other (p < 0.01). The relationships between footprint parameters and sway area were correlated only for younger children under visually deprived (eye close) and cutaneous unreliable (standing on compliant foam) conditions. This implies that the correlations between footprint parameters and sway area are very subtle which can only be observed in unreliable visual and somatosensory conditions of younger children. In addition, younger children with a lower arch height would have a smaller sway area and better posture control which might result from more cutaneous somatosensation or a flexible biomechanical structure in low arch feet during conditioned static standing.

Child↗
PubMed1983

Age-related changes in autonomic function: relationship with postural hypotension.

Eleven elderly subjects, six with signs and symptoms of postural hypotension, were investigated for autonomic neuropathy of their cardiovascular and pupillary systems. The results were compared with those from a group of nine young subjects to define the reductions in autonomic activity that normally occur with age. There was evidence of a decline in autonomic function in the elderly, but this was no greater in the group with postural hypotension. A positive correlation was found between the level of the supine systolic pressure and the degree of postural drop. It is suggested that pathology in the vasculature and not in the sympathetic innervation is responsible for postural hypotension in the elderly.

Adult↗
PubMed1991

Posture control and the risk of industrial accident: a stabilographic investigation in a naval shipyard.

In a previous case-control study on the effect of impaired perceptual acuity on the risk of industrial injuries at a naval shipyard, three factors which might influence the perception and processing of sensory impressions--alcohol consumption, hearing loss exceeding 20 decibels (dB) and exposure to noise exceeding 82 dB(A)--were found to contribute to the risk of injury. According to recent reports, these factors can all lead to impaired posture control. Because in general about 40% of all accidents are associated with falling, tripping, slipping and the like, a supplementary study has been carried out to unravel possible confounding effects of posture control on these three risk factors. Cases (who had suffered two or more accidents during the preceding 4 years) and controls (who had been accident-free in the same period) were compared as regards posture control measured during silence or noise. No significant difference in posture control was found between cases and controls, either in silence or during exposure to heavy noise.

Accidents, Occupational↗