Ergonomics: Office Chair Design and the Potential Impact on Heart Rate

According to research presented at the 2009 American Industrial Hygiene Conference and Expo, your office chair can affect more than your posture or comfort – it also might lower your heart rate.

Richard Marklin, Ph.D., of Marquette University in Wisconsin, presented "A General-Purpose Office Chair Reduces Heart Rate During Typical Office Tasks," the master's thesis of Marquette student Stephen Freier. The study set out to examine how a new type of office chair could affect tidal volume (the total amount of air brought in during every breath) and respiratory rate (breaths per minute), but instead showed that heart rate appeared to be most influenced by the design.

A conventional office chair has a wide backrest at the shoulders to provide support, and becomes narrower at the waist and hips. A new general-purpose office chair design, meanwhile, features the opposite shape – it is wide at the bottom and narrow at the top. "We call this an upwardly-tapered backrest," Marklin explained.

An ideal chair allows users to increase ventilatory (breathing) efficiency, reduce breaths per minute, increase tidal volume and also increase cardiovascular efficiency – all while the user maintains productivity. The shape of the new chair, researchers suspected, could help users breathe more efficiently.

"Because the width at the shoulders was more narrow, the hypothesis was that you would be able to expand your chest," Marklin explained.

The Study

Thirty-one participants, 15 men and 16 women with a mean age of 36, were studied in both standard office chairs and the new design. Each subject performed a sitting task for 30 minutes that was divided into 10 minutes of typing, 10 minutes of Internet searching, 5 minutes working in a spreadsheet and a 5-minute break. Next, subjects reclined in the chair and watched a movie for 30 minutes, and then performed sitting tasks for another 30 minutes.

While Marklin hypothesized that the new chair might affect respiratory rate and tidal volume, the results instead indicated a change in heart rate. Thirteen of the 16 women and 11 of the 15 men had a lower heart rate while sitting in the new chair. Men exhibited a reduced heart rate of an average of eight beats per minute; for women, their heart rates decreased an average of four beats per minute. Age and gender did not appear to impact the results.

"We did not expect this at all – for every task, there was a lower heart rate for the new chair," Marklin said. "We still don't know why."

A slower heart rate, Marklin said, often is the sign of a more efficient cardiovascular system and is a goal of many health or exercise regimens. "As resting heart rate decreases, the risk of death from cardiovascular disease decreases, too," he said. Using an office chair that can contribute to a decreased resting heart rate therefore may be considered positive for office employees.

Marklin stressed that it was not clear whether the design caused the lower rate in the new chair or if a different factor played a role, such as the chair's fabric. Marklin said future studies are being developed to segregate people according to the BMI to determine if smaller or larger body types are affected differently by the new chair design.

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