Summaries of Our Applied Research: Office Ergonomics
Summary: Subjects performed typing tasks on a desktop computer and touch-screen tablet in two chairs for an hour each, and the effects of chair, device, and their interactions on each dependent measure were recorded. Low back and overall postural loading was found to be associated with an interaction between individual, chair, and device. A lack of seat back mobility constrains individuals into an upright seating posture with increased extensor muscle forces and therefore increased compression placed onto the spine. These effects are exacerbated by increased forward flexion upon interaction with a tablet device or by slouching in the chair. It is recommended that reclined postures be assumed to allow for off-loading of the spine via the seat back. However, the extent of recline also plays a role in spinal loading while seated. In highly reclined postures, individuals tend to rotate their hips posteriorly while reclining, decreasing lumbar lordosis and increasing back extensor loading.
Summary: This study evaluated how different workstations may influence physical behavior in office work through motion and how that may affect spinal loads and discomfort. Collectively, this study suggests that a perching workstation environment represents a reasonable tradeoff between the costs and benefits of sitting and standing office workstations. This study has shown that posture supported, moderate dynamic seating or movement during office work may assist in reducing spinal loads and discomfort from standing . It appears that moderate, supported movement may have better effects when induced, particularly in the lateral (frontal) plane because it helps induce a moderate amount of workload while offsetting postural loads. This suggests that dynamic seating designs should incorporate mechanisms that have supported mobility to allow for movement to happen before the postural control system activates movement due to discomfort.
Summary: Repetitive typing may cause cumulative damage to the flexor tendons of the forearm. To address this risk, alternate keyboard designs have been introduced with novel designs such as negative tilt, split keyboard, or cup-shaped depressions for the keys. This study assessed the biomechanical impact of commercially available alternate keyboard designs. Wrist and finger goniometers measured joint motions during a standardized typing task and obtained estimates of tendon travel. The results showed that alternate keyboard designs can affect tendon travel up to about 11%, which, multiplied over time, may mean the difference between a high risk and low risk job. However, the high degree of subject variability in tendon travel may make it difficult to reduce tendon travel solely through the selection of the appropriate keyboard design. Further, these results show that keyboards that increase pitch appear to decrease tendon travel, while negative pitch keyboards increase tendon travel. Males and females responded differently to keyboard pitch angle.