2017-06-01 12:00 - Messages

Evaluating biomechanics of user-selected sitting and standing computer workstation

A standing computer workstation has now become a popular modern work place intervention to reduce sedentary behavior at work. However, user's interaction related to a standing computer workstation and its differences with a sitting workstation need to be understood to assist in developing recommendations for use and set up. The study compared the differences in upper extremity posture and muscle activity between user-selected sitting and standing workstation setups. Twenty participants (10 females, 10 males) volunteered for the study. 3-D posture, surface electromyography, and user-reported discomfort were measured while completing simulated tasks with each participant's self-selected workstation setups. Sitting computer workstation associated with more non-neutral shoulder postures and greater shoulder muscle activity, while standing computer workstation induced greater wrist adduction angle and greater extensor carpi radialis muscle activity. Sitting computer workstation also associated with greater shoulder abduction postural variation (90th–10th percentile) while standing computer workstation associated with greater variation for should rotation and wrist extension. Users reported similar overall discomfort levels within the first 10 min of work but had more than twice as much discomfort while standing than sitting after 45 min; with most discomfort reported in the low back for standing and shoulder for sitting. These different measures provide understanding in users' different interactions with sitting and standing and by alternating between the two configurations in short bouts may be a way of changing the loading pattern on the upper extremity.

Source: Lin, M. Y., Barbir, A., & Dennerlein, J. T. (2017). Applied Ergonomics.

Pre-existing low-back symptoms impact adversely on sitting time reduction in office workers

Objectives: Initiatives to reduce office-workplace sitting are proliferating, but the impact of pre-existing musculoskeletal symptoms on their effectiveness has not been determined. We assessed the influence of musculoskeletal symptoms on the outcomes of a workplace sitting intervention.
Methods: Baseline and 3-month data from a cluster-randomized controlled trial of a workplace sitting intervention (Stand Up Victoria; trial registration number ACTRN12611000742976) were used. Office workers (n = 231) from 14 work teams within one organisation were randomised (by worksite) to a multicomponent program with individual-, organisational-, and environmental-level (sit-stand workstations) change strategies; or, to a control condition (no intervention). Musculoskeletal symptoms in the low-back, upper and lower extremities (present/absent) were assessed through self-report. Linear regression models tested the moderation by baseline musculoskeletal symptoms of intervention effects on workplace sitting and standing time and on sitting and standing bout durations, assessed by the activPAL3™ activity monitor.
Results: There were significant reductions in sitting and increased standing at work (p < 0.05). However, effects varied significantly by the presence of pre-existing low-back (but not other) symptoms, with greater benefit being seen in those without symptoms. Effects on sitting time and sitting bout duration were weaker in those with low-back symptoms compared to those without by 34.6 [95% CI (0.9; 68.3)] min/8-h workday and 5.1 [95% CI (0.2; 9.9)] min, respectively. Comparable effects were seen for standing.
Conclusion: Low-back symptoms may impact on the extent to which office workers change their workplace sitting and standing time. A prudent next step to improve the effectiveness of workplace sitting-reduction initiatives such as Stand Up Victoria may be to assess and address the needs of those who displayed comparatively limited behaviour change, namely those with pre-existing low-back discomfort.

Source: Coenen, P., Healy, G. N., Winkler, E. A., Dunstan, D. W., Owen, N., Moodie, M., ... & Straker, L. M. (2017). International Archives of Occupational and Environmental Health, 1-10.

Reducing Office Workers' Sitting Time at Work Using Sit-Stand Protocols

Results From a Pilot Randomized Controlled Trial
Objective: To examine the effects of different sit-stand protocols on work-time sitting and physical activity (PA) of office workers.
Methods: Participants (n = 26, 77% women, mean age 42) were randomly allocated to usual sitting (control) or one of three sit-stand protocols (intervention) facilitated by height-adjustable workstations for a 4-week period between June and August 2015. Sitting, standing, and stepping time were assessed by inclinometry (activPAL); leisure-time physical activity (LTPA) by self-report. One-way analysis of covariance (ANCOVA) and post-hoc (Bonferroni) tests explored between-group differences.
Results: Compared with baseline, intervention groups reduced work sitting time by 113 minutes/8-hour workday (95% confidence interval [CI] [-147,-79]) and increased work standing time by 96 minutes/8-hour workday (95% CI [67,125]) without significantly impacting LTPA/sleep time.
Conclusions: Sit-stand protocols facilitated by height-adjustable workstations appear to reduce office workers' sitting time without significant adverse effects on LTPA.

Source: Li, I., Mackey, M. G., Foley, B., Pappas, E., Edwards, K., Chau, J. Y., ... & Winkler, E. (2017). Journal of Occupational and Environmental Medicine.

Development and validation of an easy-to-use risk assessment tool for cumulative low back loading

The Lifting Fatigue Failure Tool (LiFFT)
Recent evidence suggests that musculoskeletal disorders (MSDs) may be the result of a fatigue failure process in affected tissues. This paper describes a new low back exposure assessment tool (the Lifting Fatigue Failure Tool [LiFFT]), which estimates a “daily dose” of cumulative loading on the low back using fatigue failure principles. Only three variables are necessary to derive the cumulative load associated with a lifting task: the weight of the load, the maximum horizontal distance from the spine to the load, and the number of repetitions for tasks performed during the workday. The new tool was validated using two existing epidemiological databases: the Lumbar Motion Monitor (LMM) database, and a database from a U.S. automotive manufacturer. The LiFFT cumulative damage metric explained 92% of the deviance in low back disorders (LBDs) in the LMM database and 72–95% of the deviance in low back outcomes in the automotive database (depending on the outcome measure). Thus, LiFFT is practitioner friendly and its cumulative damage metric highly related to low back outcomes.

Source: Gallagher, S., Sesek, R. F., Schall, M. C., & Huangfu, R. (2017). Applied Ergonomics.

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