Monitoring the use of chair backrest and forearm support during computer work with and without a workplace butterfly board attachment

In this thesis, a new method is proposed for monitoring the use of backrest and forearm support during computer work on a standard workstation and the same workstation with a Butterfly board attachment. The developed techniques measure the effect of using the Butterfly board on the resting duration and the pressure on the back and forearms while resting. Novel(TM) pressure sensor mats were used to measure pressure applied by resting against the chair back rest and the arm rests. To ensure that the back mat is not moving, a new technique of mapping the back points of contact with the backrest is used. A video camera, synchronized with the pressure measurement system, is used to identify the location where the forearms were resting (work surface or chair arm rests). Peak pressure data were analyzed using Amplitude Probability Density function and visual display comparisons between resting patterns for both workstation setups. The resting duration is evaluated by calculating the number of zero pressure values when the backrest and arm support were not utilized. The center of pressure trajectory length, travel velocity and area of displacement were also calculated and compared between the two setups. Finally, a subjective body map is used to compare the discomfort level in different body parts after testing on each setup. It was found that the Butterfly board significantly improved the usage of back rest (p=0.04) with longer resting duration and no significant difference in the area of contact. Discomfort scale results showed a significant decrease in tension for the upper and lower back. For the forearm, the results were mixed. The Butterfly board eliminated points of excessive pressure in the wrist area and pressure was more evenly distributed on the mat. The peak pressure values were significantly lower while using the Butterfly board (p=0.02) and (p=0.004) for the right and left forearms respectively. This may be due to the effect of the gel pad provided for wrist support. On the other hand, no significant difference in the resting duration or the mat area of contact were found but discomfort scale results showed a significant in lowering of tension on the neck and shoulders.