Lumbar posture and trunk muscle activation during static and dynamic seated tasks on a novel dynamic ergonomic chair

peer-reviewedLow back pain (LBP) is a common musculoskeletal disorder and prolonged sitting often aggravates LBP. A novel dynamic ergonomic chair (‘Back App’), which facilitates less hip flexion while sitting on an unstable base has been developed. This study compared lumbar posture and trunk muscle activation on this novel chair with a standard backless office chair. Twelve painfree participants completed a typing task on both chairs. Lumbar posture and trunk muscle activation were collected simultaneously and were analysed using paired t-tests. Sitting on the novel dynamic chair significantly (p 0.05) between chairs. Maintaining lordosis with less muscle activation during prolonged sitting could reduce the fatigue associated with upright sitting postures. Studies with longer sitting durations, and in people with LBP, are required. Practitioner Summary: Sitting on a novel dynamic chair resulted in less lumbar flexion and less back muscle activation than sitting on a standard backless office chair during a typing task among pain-free participants. Facilitating lordotic sitting with less muscle activation may reduce the fatigue and discomfort often associated with lordotic sitting postures.ACCEPTEDpeer-reviewe

Photographic measurement of upper-body sitting posture of high school students: A reliability and validity study

<p>Abstract</p> <p>Background</p> <p>All the reported measures of sitting posture, as well as photographs, have one flaw, as these measures are external to the body. These measures use calculations from external bony landmarks to estimate spinal posture, on the understanding that what is being measured externally reflects the shape, health and performance of structures of the underlying spine. Without a comparative measure of the relative position of the structures of the spine, the validity of any external spinal posture measure cannot be established. This paper reports on a study which tests the validity of photographs to measure adolescent sitting posture.</p> <p>Methods</p> <p>The study was conducted in a laboratory at the Department of Human Biology, University of Cape Town. A random sample of 40 adolescents were recruited from the Cape metropolitan schools, to detect differences of three degrees or more between the repeated measures of upright, normal or slouched posture (photographs) and between the posture photographs and LODOX measures. Eligible participants were healthy male and female subjects aged 15 or 16 years old, in Grade 10, and who were undertaking Computer or Computype studies at their schools. Two posture measurement tools were used in the study, namely: Photographs were taken using the Photographic Posture Analysis Method (PPAM) and Radiograph<it>s </it>were taken using the LODOX (LODOX (Pty) Ltd) system. Subjects' posture was assessed in simulated computer workstations. The following angles were measured: the sagittal head angle, cervical angle, protraction/retraction angle, arm angle and the thoracic angle.</p> <p>Results</p> <p>Data from 39 subjects (19 males, 20 females) was used for analysis (17 15-year-olds (7 boys and 10 girls), 22 16-year-olds (12 boys and 10 girls)). All but one photographic angle showed moderate to good correlation with the LODOX angles (Pearson r values 0.67–0.95) with the exception being the shoulder protraction/retraction angle Pearson r values. Bland Altman limits of agreement illustrated a slight bias for all angles. The reliability study findings from repeated photographs demonstrated moderate to good correlation of all angles (ICC values 0.78–0.99).</p> <p>Conclusion</p> <p>The findings of this study suggest that photographs provide valid and reliable indicators of the position of the underlying spine in sitting. Clinically it is important to know whether a patient is showing true progression in relation to a postural intervention. Based on the results of this study, the PPAM can be used in practice as a valid measure of sitting posture.</p

The potential for actigraphy to be used as an indicator of sitting discomfort

Objective: A novel technique that uses actigraphy, the study of activity involving the use of body-mounted accelerometers, to detect the discomfort-related movements of a sitting individual has been proposed as a potential indicator of sitting discomfort, and the purpose of this study was to test its validity. Background: Objective measurement of sitting discomfort has always been challenging for researchers. Electromyographic measurements, pressure mapping, and a wide range of other techniques have all been investigated with limited success. Method: The activity monitor’s ability to detect and measure seated movement was assessed, and 12 participants were tested on four different chairs (100-min sessions for each). Results: The activity monitor was able to detect par-ticipants ’ sitting movements (Pearson coefficients&gt; 0.9). The chairs were shown to have significantly different subjective discomfort ratings, all of which increased over time. The movements detected by the activity monitor also increased significantly with time, and the amount measured was greater in the chairs rated as most uncomfortable. Regression analysis indicated that the actigraphy data were able to account for 29.6 % of the varia-tion in perceived discomfort ratings. Conclusion: Actigraphy can reliably detect sitting movements and may be of use in measuring sitting discomfort. Application: Potential applications of this technique exist for seating research in the automotive industry, health care, and office and leisure chairs

Analysis of Discomfort During a 4-Hour Shift in Quay Crane Operators Objectively Assessed Through In-Chair Movements

This study aims to investigate the existence of possible changes in postural strategies adopted by quay crane operators during a 4-h shift performed in a simulated environment. In particular, the analysis is carried out by analyzing the trend of in-chair-movement (ICM) as indicator of discomfort and fatigue. Using a pressure sensitive mat placed on the seat pan, average and peak body-seat pressure and trunk center-of-pressure (COP) time series were acquired and processed to calculate ICMs with two methods based on pressure changes and one which considers the COP shifts. The results show a well-defined linear trend for ICM, which was detected by all the tested approaches, with significant increases occurring after 45–60 min from the beginning of the shift. However, the method which employs COP data appears potentially more adequate to accurately identify ICM due to its relative insensitivity to external factors associated with individual’s anthropometry and body composition and presence of external vibrations. Future developments of the study will be focused on establishing the suitability of the method as non-invasive early predictor of fatigu