Physiological Motion Axis for the Seat of a Dynamic Office Chair

Applied Ergonomics, 2012

Prolonged and static sitting postures provoke physical inactivity at VDU workplaces and are therefore discussed as risk factors for the musculoskeletal system. Manufacturers have designed specific dynamic office chairs featuring structural elements which promote dynamic sitting and therefore physical activity. The aim of the present study was to evaluate the effects of four specific dynamic chairs on erector spinae and trapezius EMG, postures/joint angles and physical activity intensity (PAI) compared to those of a conventional standard office chair. All chairs were fitted with sensors for measurement of the chair parameters (backrest inclination, forward and sideward seat pan inclination), and tested in the laboratory by 10 subjects performing 7 standardized office tasks and by another 12 subjects in the field during their normal office work. Muscle activation revealed no significant differences between the specific dynamic chairs and the reference chair. Analysis of postures/joint angles and PAI revealed only a few differences between the chairs, whereas the tasks performed strongly affected the measured muscle activation, postures and kinematics. The characteristic dynamic elements of each specific chair yielded significant differences in the measured chair parameters, but these characteristics did not appear to affect the sitting dynamics of the subjects performing their office tasks.

BioMed Research International, 2013

Increasing numbers of people spend the majority of their working lives seated in an office chair. Musculoskeletal disorders, in particular low back pain, resulting from prolonged static sitting are ubiquitous, but regularly changing sitting position throughout the day is thought to reduce back problems. Nearly all currently available office chairs offer the possibility to alter the backrest reclination angles, but the influence of changing seating positions on the spinal column remains unknown. In an attempt to better understand the potential to adjust or correct spine posture using adjustable seating, five healthy subjects were analysed in an upright and reclined sitting position conducted in an open, upright MRI scanner. The shape of the spine, as described using the vertebral bodies' coordinates, wedge angles, and curvature angles, showed high inter-subject variability between the two seating positions. The mean lumbar, thoracic, and cervical curvature angles were 29±15 ∘ , −29±4 ∘ , and 13±8 ∘ for the upright and 33±12 ∘ , −31±7 ∘ , and 7 ± 7 ∘ for the reclined sitting positions. Thus, a wide range of seating adaptation is possible through modification of chair posture, and dynamic seating options may therefore provide a key feature in reducing or even preventing back pain caused by prolonged static sitting.

International Journal of Environmental Research and Public Health

Employing dynamic office chairs might increase the physical (micro-) activity during prolonged office sitting. We investigated whether a dynamic BioSwing® chair increases chair sway and alters trunk muscle activation. Twenty-six healthy young adults performed four office tasks (reading, calling, typing, hand writing) and transitions between these tasks while sitting on a dynamic and on a static office chair. For all task-transitions, chair sway was higher in the dynamic condition (p < 0.05). Muscle activation changes were small with lower mean activity of the left obliquus internus during hand writing (p = 0.07), lower mean activity of the right erector spinae during the task-transition calling to hand writing (p = 0.036), and higher mean activity of the left erector spinae during the task-transition reading to calling (p = 0.07) on the dynamic chair. These results indicate that an increased BioSwing® chair sway only selectively alters trunk muscle activation. Adjustments of chai...

Medicine, 2020

Lumbar and pelvic alignment may have a huge impact on the posture of the spine and other parts. The aim of this study were to compare the spinal curvature of the cervical, thoracic, and lumbar spine and the muscle activity of the cervical erector spinae muscle, upper trapezius muscle, and thoracic erector spinae muscle when sitting at 3 different sloped, seating surfaces. A 10°wedge was used as the seating surface and we compared a forward sloping seat surface, a flat seating surface, and a rear sloping seat surface, in that order. Twenty healthy officers were recruited for this study. The subjects sat on the seat of 3 different slopes and watched a total of 3 videos, 10 minutes each. The rest time was 10 minutes. Subjects were photographed while viewing videos and muscle activity was measured. There were significant differences in cervical, thoracic, lumbar curvatures, and muscle activity in the 3 different sitting positions according to seat tilt (P < .05). Among the 3 slopes, the forward slope decreased forward head posture and cervical erector spinae muscle activity (P < .05). The activity of the cervical erector spinae muscle was 2.67% with a forward sloping seat, 5.45% with a flat sloping seat, and 6.77% with a rear sloping seat, revealing a significant difference (P < .05). This suggests that a forward sloping seat surface was effective in maintaining a neutral alignment of the spine, and this decreased the cervical spine erector muscle activity. Based on this result, equipment and chair development to incline seats forward may improve posture and health, and prevent chronic pain. Abbreviations: CES = cervical erector spinae muscle, CVA = craniovertebral angle, FHP = forward head posture, MVC = maximal voluntary contractions, TES = thoracic erector spinae muscle, UT = upper trapezius muscle.

Ergonomics, 2001

Seated work has been shown to constitute a risk factor for low-back pain. This is attributed to the prolonged and monotonous low-level mechanical load imposed by a seated posture. To evaluate the potential health eOE ects with respect to the low back of o ce chairs with a movable seat and back rest, trunk kinematics, erector spinae EMG, spinal shrinkage and local discomfort were assessed in 10 subjects performing simulated o ce work. On three separate occasions subjects performed a 3 h task consisting of word processing, computer-aided design and reading. Three chairs were used, one with a ® xed seat and back rest and two dynamic chairs, one with a seat and back rest movable in a ® xed ratio with respect to each other, and one with a freely movable seat and back rest. Spinal shrinkage measurements showed a larger stature gain when working on the two dynamic chairs as compared with working on the chair with ® xed seat and back rest. Trunk kinematics and erector spinae EMG were strongly aOE ected by the task performed but not by the chair type. The results imply that dynamic o ce chairs oOE er a potential advantage over ® xed chairs, but the eOE ects of the task on the indicators of trunk load investigated were more pronounced than the eOE ects of the chair.

The Scientific World Journal, 2012

Sitting is the most frequently performed posture of everyday life. Biomechanical interactions with office chairs have therefore a long-term effect on our musculoskeletal system and ultimately on our health and wellbeing. This paper highlights the kinematic effect of office chairs on the spinal column and its single segments. Novel chair concepts with multiple degrees of freedom provide enhanced spinal mobility. The angular changes of the spinal column in the sagittal plane in three different sitting positions (forward inclined, reclined, and upright) for six healthy subjects (aged 23 to 45 years) were determined using an open magnetic resonance imaging (MRI) scanner. An MRI-compatible and commercially available office chair was adapted for use in the scanner. The midpoint coordinates of the vertebral bodies, the wedge angles of the intervertebral discs, and the lumbar lordotic angle were analysed. The mean lordotic angles were 16.0 ± 8.5 • (mean ± standard deviation) in a forward inclined position, 24.7 ± 8.3 • in an upright position, and 28.7 ± 8.1 • in a reclined position. All segments from T10-T11 to L5-S1 were involved in movement during positional changes, whereas the range of motion in the lower lumbar segments was increased in comparison to the upper segments.

2014

While data on postures exhibited by users on office tasks chairs are available; similar information for office side chairs are lacking. The purpose of this study was to collect posture data exhibited by individuals sitting in an office side chair for a period of two hours. Five side chairs differing in seat pan, backrest and armrest designs were utilized in the study. Ten participants were required to watch a two hour video while seated in a randomly assigned side chair over a period of 5 days. During a testing session, user postures were recorded at 15-minute intervals. Pressure map of seat pan and subjective responses using Shackel scale were also collected at pre-determined time periods. Pressure map data for 7 postures (reclined, upright, forward bending, pronounced lean (left/right), and crossed legs (left/right)) were also collected at the start and end of a session. Results from this study will provide information on sitter self-selected postures, and potential influence of s...

European Spine Journal, 2011

Low back pain is regarded as the primary cause of occupational disability in many countries worldwide. However, there is a lack of valid assessment of kinematic spine and trunk parameters to provide further insight into occupational spine loads. A new 3-dimensional mobile measurement system (3D-SpineMoveGuard) was developed and evaluated by means of repeated dynamic and isometric trunk positions by 10 male and 10 female volunteers. The interclass correlation coefficient indicates high test-retest reliability (r = 0.975-0.999) of the 3D-Spine-MoveGuard. Moreover, analysis of validity revealed almost identical results for the new measurement system. The evaluation study indicates a good scientific quality for the use in occupational task analyses. The objective assessment of indirectly measured spine and trunk kinematics will give further insight to predict and prevent job-related spine loads.

Human Factors and …, 2008

Journal of sport rehabilitation, 2017

Clinical evaluation of the spine is commonplace in musculoskeletal therapies such as physiotherapy, physical medicine/rehabilitation, osteopathic, and chiropractic clinics. Sit-to-stand (STS) is one of the most mechanically demanding of daily activities and crucial to independence. Difficulty or inability to perform STS is common in individuals with a variety of motor disabilities such as low back pain. The purpose of this systematic review was to evaluate available evidence in literature to determine 2D and 3D kinematics of the spine during STS in patients with LBP and healthy young adult participants using motion analysis systems (electromagnetic and marker based). Electronic databases PubMed/Medline (NLM), Scopus, Science Direct, and Google scholar were searched between January 2002 and February 2017. Additionally, the reference lists of the articles that met the inclusion criteria were also searched. Prospective studies published in peer-reviewed journals, with full text availab...