Evaluation of RH Logic 400 office chair Influence on comfort, physical loads and performance during computer work

Rapport, 2013

Today there is a large amount of knowledge about ergonomics and working sitting postures during long hours of office computer work. There is also a large selection of office chairs available on the market with numerous possibilities of individual adjustments for optimal and varied sitting postures. For the manufacturers it is of great interest to show advantages such as increased productivity, decreased discomfort and reduced physical disorders as well as improved health and well-being when their ergonomic chairs are used at work. For optimal usage it is important that the users take advantage of all the ergonomic features offered. However, often problems arise when a chair has a large amount of settings with various design and functionality. It is difficult without instructions and training to understand how the various settings work and how they should be handled and adjusted optimally for a specific individual. The purpose of this study was to examine if the possibilities that the RH Logic 400 office chair offers to create an ergonomic, individual and varied working posture were employed optimally by the users and also what effects the features had on comfort and work performance. The goal was to determine if positive effects regarding comfort, health and performance arise during 5 weeks of office computer work. Furthermore the goal was to find out how the RH chair and its adjustments were perceived and handled by the users when they were informed in different ways during introduction of the chair in their company. 84 office computer workers at two companies participated in the study during a period of five weeks. 48 of workers got the RH Logic 400 office chair, while the others kept their ordinary office chairs. These functioned as a control group. Among the RH chair users, 28 received an verbal introduction/training session of the chair’s functions from a manufacturer sales person together with a physiotherapist. The others only got access to a small written information brochure from the manufacturer hanging under the chair. Before the study all participants filled in a comprehensive questionnaire about their personal data, working situation and health status. Then they answered a questionnaire each week during a five weeks period about their health and well-being status as well as if the had adjusted their chair and used its features. Finally another comprehensive questionnaire was filled out when the test period was finished. In total 18000 data points were collected from 7 questionnaires (together including 82 questions with sub-questions). The data was statistically analysed using Wilcoxons signed-rank test and Student’s t-test. The significant level was set to 5%. The concluding results from the study showed that the RH Logic 400 chair significantly decreased the physical strain in the neck, shoulder and lumbar regions, and for the shoulders on the right hand side. People with previous long-term physical problems in the upper part of their body perceived decreased distress after five weeks work in the RH chair. The sitting posture and the comfort were perceived better for the RH chair than in the test subjects’ previous chair. They also felt more relaxed in the RH chair. However the chair and back cushions of the RH chair were perceived stiffer than in their previous chair. The RH office chair had a positive impact on the working situation as a whole, but did not affect the stress level at work. When discussing work performance and stress all parts in the working environment have an effect on well-being and it is therefore difficult to separate effects from the chair. The understanding about how the adjustments of the RH chair should be performed, as well as usage of the rocking function, increased significantly when verbal presentation and training were given, as well as how often the adjustments were used. However, when the users had found suitable settings, they did seldom adjust their chairs again during the test period. Sitting height was the measure that most often was adjusted while the positions of the neck rest and arm rests seldom were changed. The recommendation from this study is that when delivering office chairs to customers it is very important to introduce the users on how to adjust and handle the chair to accomplish optimal individual settings. Also point out that the chair should be adjusted several times a day and the rocking function should be used frequently to achieve necessary posture changes. Furthermore, explicit written information material need to be developed, explaining how good individual ergonomic working postures can be found by adjusting the chair’s different settings properly and also in which order the settings should be performed.