Constrained Posture Research Articles

Ergonomics of work space: Changing dynamics on OCRA evaluation and work aids

The work space is the sancto sanctorum of the world’s economy. It has become increasingly clear that a functional, efficient work space is conducive to optimum output. Therefore the engineering concepts of comfort and ease of working for long durations have become the mainstay of industries the world over. These concepts are complemented by the inputs of safety, hygiene and worker friendliness especially in the global garment manufacturing industry. They need to be evaluated scientifically. One of these means is the evaluation by using OCRA. The basic concept of OCRA, therefore, is to determine and measure a defined technical action. It examines the series of complex movements necessary to complete a work task, involving the upper limb joints at the shoulder, elbow, wrist and finger level. Various scholars have documented the root causes of musculoskeletal discomfort among the seated workers and have delineated them as the constrained work posture and repetitive tasks. Currently, the researcher is working on three work aid prototypes by incorporating workstation design principles for modifications to improve working posture.

THE IMPACT OF OCCUPATIONAL RISK FACTORS ON THE DEVELOPMENT OF LOWER BACK PAIN IN INDUSTRIAL WORKERS

Introduction. Spondylogenic back pain is common in the working-age population and often results in a working disability. In order to ensure professional decision-making and inform preventive measures, occupational risk factors for low back pain (LBP) need to be identified. Material and methods. Using a regular medical check-up examination data, we analyzed the prevalence and the odds ratio of LBP in 3215 individuals working in physically demanding jobs and exposed to physical inactivity and vibration. Results. No statistically significant differences in LBP prevalence were found between workers exposed to low total physical activity (PA), in and out of work, and those exposed to physical overwork (38.9% и 33.8% respectively). Physical inactivity in the workplace and hypodynamia during leisure-time cause similar effects and increase the risk of LBP by 1.5 times. A combination of occupational factors such as a constrained posture (class 3.1-3.2 according to the National Labor Legislation) and whole-body vibration increases LBP risk up to 78.7%. Whereas the combination of a constrained posture, prolonged sedentary position, and whole-body vibration, increases LBP prevalence up to 84.21% (OR: 80). Conclusions. The highest risk of LBP (OR: 80.0) was assigned to the combination of constrained posture, prolonged sedentary position, and whole-body vibration. The obtained data suggest that both low PA and physical overwork increase the risk of LBP, whereas moderate PA reduces it.

Prevalence of Work Related Low Back Pain among Physical Therapists with Different Foot Postures at Fayoum, Egypt: A Survey Study

AbstractBackground: Low Back Pain (LBP) is the commonest form of musculoskeletal disorder among physical therapists. Repetitive tasks, high force manual techniques bending/twisting postures, patient transfer assisting with mat activities, lifting heavy equipment, prolonged constrained posture and foot abnormalties identified as risk factors of low back pain which is common in the field of physical therapy.Aim of the Study: The purpose of this study was to identify prevalence of work related LBP among physical therapists with different foot postures working in governmental hospitals in fayoum-Egypt.Subjects and Methods: 147 physical therapists who are working in the governmental hospitals in Fayoum-Egypt, the LBP will be measured by Nordic Questionnaires (NQ) and foot postures measured by Foot Posture Index (FPI).Results: 112 of the 147P. Ts (76.19%) have completed the questionnaire. WRLBP (n=68), non WRLBP (n=25), no LBP (n=19). The lifetime prevalence of WRLBP was 60.71%, the twelve-month prevalence of WRLBP was 52.67%, the point prevalence of WRLBP was 47.32%, concerning BMI and WRLBP 74.28% of subjects with BMI of 20-24.9kg/m2 and 54.54% of subjects with BMI of 25-29.9kg/m2, the WRLBP was present in 54.83% of female subjects and in 68% of male subjects, the WRLBP was present in 56% of subjects with normal foot posture, 55% of subjects with pronated foot posture, 91% of subjects with highly pronated foot posture, 100% of subjects with supinated foot posture and 67% of subjects with highly supinated foot posture.Conclusion: There was no statistically significant associ-ation between LBP and foot postures, however there was a statistically significant association between WRLBP and BMI. There was a high prevalence of WRLBP among physical therapists who working in governmental hospitals in Fayoum-Egypt.

Constrained posture in dentistry \u2013 a kinematic analysis of dentists

BackgroundHow a dentist works, such as the patterns of movements performed daily, is also largely affected by the workstation Dental tasks are often executed in awkward body positions, thereby causing a very high degree of strain on the corresponding muscles. The objective of this study is to detect those dental tasks, during which awkward postures occur most frequently. The isolated analysis of static postures will examine the duration for which these postures are maintained during the corresponding dental, respectively non-dental, activities.Methods: 21 (11f/10 m) dentists (age: 40.1 ± 10.4 years) participated in this study. An average dental workday was collected for every subject. To collect kinematic data of all activities, the CUELA system was used. Parallel to the kinematic examination, a detailed computer-based task analysis was conducted. Afterwards, both data sets were synchronized based on the chronological order of the postures assumed in the trunk and the head region. All tasks performed were assigned to the categories “treatment” (I), “office” (II) and “other activities” (III). The angle values of each body region (evaluation parameter) were examined and assessed corresponding to ergonomic standards. Moreover, this study placed a particular focus on static positions, which are held statically for 4 s and longer.ResultsFor “treatment” (I), the entire head and trunk area is anteriorly tilted while the back is twisted to the right, in (II) and (III) the back is anteriorly tilted and twisted to the right (non-neutral position). Static positions in (I) last for 4–10s, static postures (approx. 60%) can be observed while in (II) and (III) in the back area static positions for more than 30 s are most common. Moreover, in (II) the back is twisted to the right for more than 60 s in 26.8%.ConclusionAwkward positions are a major part of a dentists’ work. This mainly pertains to static positions of the trunk and head in contrast to “office work.” These insights facilitate the quantitative description of the dentist profession with regard to the related physical load along with the health hazards to the musculoskeletal system. Moreover, the results allow for a selective extraction of the most unfavorable static body positions that dentists assume for each of the activities performed.

Effect of Constrained Arm Posture on the Processing of Action Verbs.

Evidence is increasing that brain areas that are responsible for action planning and execution are activated during the information processing of action-related verbs (e.g., pick or kick). To obtain further evidence, we conducted three experiments to see if constraining arm posture, which could disturb the motor planning and imagery for that arm, would lead to delayed judgment of verbs referring to arm actions. In all experiments, native Japanese speakers judged as quickly as possible whether the presented object and the verb would be compatible (e.g., ball–throw) or not (e.g., ball–pour). Constrained arm posture was introduced to the task by asking participants to keep both hands behind their back. Two types of verbs were used: manual action verbs (i.e., verbs referring to actions performed on an object by a human hand) and non-manual action verbs. In contrast to our hypothesis that constrained arm posture would affect only the information processing of manual action verbs, the results showed delayed processing of both manual action and non-manual action verbs when the arm posture was constrained. The effect of constrained arm posture was observed even when participants responded with their voice, suggesting that the delayed judgment was not simply due to the difficulty of responding with the hand (i.e., basic motor interference). We discussed why, contrary to our hypothesis, constrained arm posture resulted in delayed CRTs regardless of the “manipulability” as symbolized by the verbs.

Evaluation of Low Back and Neck Pain and Disability of Interns at Physiotherapy and Rehabilitation Department of Afyon Kocatepe University

Repetitive tasks, high force, direct pressure, and awkward joint and prolonged constrained posture are cited as prime risk factors, making particularly younger adult physiotherapists vulnerable to musculoskeletal injury. Fourth-grade students (interns) perform clinical practice at Afyon Kocatepe University Hospital. They apply hydrotherapy, electrotherapy, robotic therapy, virtual reality therapy and exercise therapy to patients (inpatient and outpatient) at both orthopaedic and neurology units approximately twelve months. Because we think they are under the risk of low back and neck disorders therefore aim of the present study is to evaluate recent low back and neck pain and disability of them. 50.6% participants had recent low back pain; 52.9% participants reported mild and moderate low back disability. 21.8% participants had recent neck pain; 16% participants showed mild, moderate and severe neck disability. The difference between units related to low back and neck pain or disability wasn’t significant statistically (p>0.05). Most participants announced that they used the body biomechanics correctly (84.1%) and took care of ergonomic conditions (91.5%). In conclusion, it is vital to identify prevalence of low back and neck pain among physiotherapy students and take necessary precautions to prevent further problems.

A robust back-stepping based trajectory tracking controller for the tanker with strict posture constraints under unknown flow perturbations

This paper proposes a novel robust back-stepping based trajectory tracking controller for the tanker with strict posture constraints under unknown flow perturbations in Autonomous Aerial Refueling (AAR). Firstly, by using the back-stepping technique, the proposed trajectory tracking control law design is separated into five loops. The 6 DOF model for tanker is tactfully transformed into several strict-feedback nonlinear forms, especially the dynamics of the translational kinematics which are originally non-affine nonlinear forms and are intractable for controller design. The influences of the unknown flow perturbations on tanker in each loop are viewed as the components of the “total disturbances” which are estimated and compensated by extended state observer (ESO). Secondly, the uncontrolled Euler angle constraints, which should also be considered in AAR, are transformed into extra boundary commands for the angular rates. And a novel command limiting tracking differentiator (CLTD), which considers not only the controlled but also uncontrolled state constraints, is specially designed for posture control. Thirdly, an integrated robust constrained posture control scheme is proposed for tanker's posture constraints based on Barrier Lyapunov (BL) function and CLTD. Then, with the position and ground velocity controller based on traditional active disturbance rejection control (ADRC) in the outer loop, a novel robust back-stepping based trajectory tracking controller is proposed for tanker in AAR. Finally, extensive simulations and comparisons on the 6 DOF tanker model are carried out to demonstrate the effectiveness of the proposed control scheme.

Constrained postures and spatial S-R compatibility as measured by the Simon effect.

Whereas working under constrained postures is known to influence the worker's perceived comfort and health, little is known in regard to its influence on performance. Employing an Auditory Simon task while varying posture, we investigated the relationship between constrained postures and cognitive processes in three experiments. In Experiment 1 and 2, participants operated a rocker switch or a control knob with one hand either in front or in the back of their body and while either sitting or kneeling. Perceived musculoskeletal exertion was gathered with a questionnaire. Results of the first two experiments showed differently perceived comfort and a minor effect of constrained posture on cognitive performance. However, results indicated that spatial coding in the back compares to either a virtual turn of the observer towards the control device (front-device coding) or along the observer's hand (effector coding). To clarify this issue the rocker switch was operated with one or two hands in Experiment 3, showing a comparable coding only in the one-hand condition and indicating evidence for the effector-coding hypothesis in the back.

Continuous assessment of back and upper arm postures by long-term inclinometry in carpet weavers

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h.Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.

The increased foreperiod duration to attain the neutral optimal preparation from sitting to standing

The purpose of the present experiment was to investigate the effects of a neutral preparation during the foreperiod on motor and postural programming processes in a voluntary upper limb movement. The foreperiod duration (300, 500, 700 and 900 ms) and the postural condition (sitting vs standing) were manipulated using a neutral preparation (no advanced information during the preparatory signal). Thirteen subjects performed a raising arm movement with 1 kg load at the wrist. Premotor time, latency of the anticipatory postural adjustments and the vertical torque were calculated. A previous experiment showed that the optimal foreperiod duration (i.e. leading to the shortest premotor time) increased from sitting to standing in a selective preparation (Cuisinier et al. in Brain Res Bull 66(2):163-170, 2005). The present experiment replicated this finding in a neutral preparation. It was found that (1) this optimal foreperiod duration still increased from 500 ms in sitting to 700 ms in standing in a neutral preparation, (2) this increased optimal foreperiod duration resulted from a greater level of alertness necessary to control a more constrained posture in standing than in sitting, and (3) the existence of a temporal modulation in the central organization of the postural and focal commands was according to the foreperiod duration.

Fingertip Forces While Using three Different Keyboards

The relationship of chronic musculoskeletal disorders, such as carpal tunnel syndrome and wrist tendinitis, to prolonged alphanumeric keyboard use is controversial. Known risk-factors for these disorders, such as repetition of task, forceful exertions, awkward joint postures, direct mechanical pressure, and prolonged constrained posture, may be applicable to keyboard use. In this study fingertip forces were measured for 10 typists using three alphanumeric keyboards that differed only in their key force and displacement characteristics. While subjects typed, peak fingertip force was collected for each keystroke using strain gauge load cells. The mean peak fingertip forces applied by all subjects for all keys for the three keyboards were 193 gm, 182 gm and 220 gm; significantly different means. The 18% reduction in fingertip force in the second keyboard compared with the third is attributed to a higher minimum force of activation and a higher force at total key travel in the third keyboard. This study indicates that keyboard key force-displacement characteristics can be altered to reduce the fingertip forces applied by typists and theoretically this may reduce the risk of developing chronic musculoskeletal disorders.

Back pain and exposure to whole body vibration in helicopter pilots

In a questionnaire survey the prevalence of back pain in 163 helicopter pilots was compared to that in a control group of 297 non-flying air force officers who underwent the same pre-employment medical examination. Since pilots document their hours of flight in a personal flight log, an accurate estimate of the duration of exposure could be made. In addition, vibration levels of the helicopters were measured and an accumulative vibration dose was calculated for each pilot. 'Transient' back pain of a short duration was more frequent amongst the pilots compared to the control group, and the prevalence of 'chronic' back pain of a persistent nature was also higher amongst the helicopter pilots. Transient back pain seemed to be most strongly related to the average hours of flight per day, whereas chronic back pain was more closely related to total hours of flight or the accumulative vibration dose. A significant higher prevalence of this chronic back pain was observed only after 2000 hours of flight or a vibration dose of 400 m2h/s4. The observed health effects may be due to vibration or constrained posture but are most likely due to concomitant exposure to both factors.

Health Hazards Associated with Constrained Posture in Visual Display Terminal Workplaces

Health Hazards Associated with Constrained Posture in Visual Display Terminal Workplaces

A Study on the Posture of the Operator in Dental Treatment

There has been much literature published on the subject of working postures of various operators, which are regarded as being important from human engineering and industrial medicine points of view. However, studies on working postures of the dentist are scanty. In view of the fact that individual dentists assume their own particular postures, the author carried out the present study as part of a series of researches on the occupational and hygienic study of the dentist, conducted for a long time by the Department of Hygiene and Public Dental Health where the author belongs. In the belief that the working posture of a dentist might exert some influence on his spinal column, observations were mode of the occlusal plane angle, inclination of the back of dental chair and position assumed in terms of various treatment spots and contents. As the same time, radiograms were taken of the spinal column and photographs were also taken of various working postures. An artificial spinal column was constructed from these data and careful analyses of changes in the artificial spinal column revealed the following conclusions:1) Angles of the occlusal plane.On the average, 27.1° and 23.8° were respectively measured for the treatment of upper and lower jaws in a standing position. In a sitting position, on the other hand, the measured values were 46.6° for the upper and 37.4° for the lower jaw respectively. In either position, the angles were found to be larger in the treatment of the upper jaw.2) Inclination of the chair back.On the average, 130.8° and 128.8° were respectively measured for the treatment of upper and lower jaws in a standing position. In a sitting position, on the other hand, the inclinations were 155.8° for the upper and 252.9° for the lower jaw. Here again, upper jaw revealed the tendency of a slight increase over the lower jaw.3) Treatment positions.In a standing position, 8.8 o'clock and 9.0 o'clock were measured for the upper and lower jaws respectively. On the other hand, in a sitting position the measured values were 9.8 o'clock and 9.9 o'clock for the upper and lower jaws. In either case, the lower jaw revealed somewhat higher values.4) As for the lateral curvature of the spinal colum on the part of dentists, those who were above 4° gave an incidence of 52.2%. Distorsion of the spinal column was seen in 87.0% of dentists. The distorsion in many cases was either to the right or in the form of an S and, for this reason, it was thought that unnatural or constrained posture assumed in dental treatment had some bearing on this phenomenon.5) About 5.9 vertebrae per dentist suffered from the lateral curvature and these were chiefly concentrated around Th, 8 and Th, 9 thoracal vertebrae.6) The simulation of various movements revealed the following facts. That is, at a standing position the body tended to incline itself forward to the right around the Th, 7 thoracal vertebra, while a distorsion made the cervical region turn to the left. In a sitting position, on the other hand, there was observed a tendency that a backward bending occurred from the Th, 12 thoracal vertebra to the lumbar region.7) From these findings, it is urged that those conditions should be established which willmaintain the safety of spinal column on the part of dentists engaged in treatment.8) From a standpoint of health control of dentists, it is thought desirable that some kind of exercises to rotate and extend the spinal column should be routinely performed.