Date of Award

Fall 2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Richard W. Marklin

Second Advisor

Paula E. Papanek

Third Advisor

Vikram Cariapa

Abstract

Most office chairs have a backrest that is wider at the shoulders than at the hips. Recently, a new office chair was developed that has a backrest that is narrower at the shoulders and wider at the hips (upwardly tapered backrest). The upwardly tapered backrest should allow users to increase their ventilatory efficiency, compared to a conventional, wide backrest. This new backrest design will hypothetically allow a user to retract their scapulae, increase expansion of the chest cavity, thus allowing the lungs more space to expand. Specific measures of improved ventilatory efficiency are an increase in tidal volume (Vt - liters/breath) and a decrease in respiratory rate (RR - breaths/min).

Ventilatory and cardiovascular metabolic variables were measured from 31 office workers sitting in 2 chairs (conventional and upwardly tapered). The Cortex Metamax 3B system (Leipzig, Germany) was used to measure VO2 , RR, Vt and heart rate (HR - beats per min). Each participant performed 8 tasks in each chair. The tasks included typing, searching the internet, creating a spreadsheet, and watching a movie. Physiologic data were collected throughout testing. The subjects were blinded to which chair the test chair was. Results indicated no significant differences in users' RR and Vt between the two chairs, but the users did have a significantly lower HR when they sat in the chair with the upwardly tapered backrest (3 to 7 bpm less). Heart rate has been shown to be a risk factor of heart disease, and thus the test chair could reduce the impact of a risk factor of heart disease in office workers. Analysis of subjective assessment data did not show any overall preference for either chair.