The influence of wearing a wallet in your sitting posture - A quantitative study using an intelligent chair

Leonardo Martins, Inês Marques, Rui Almeida, Jessica Costa, Claudia Quaresma, Pedro Vieira

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Citation (Scopus)


Wearing an object in the rear pocket alters the interface between the body and the chair, leading to the compression of the sciatic nerve. Prolonged sitting behaviors with such objects can lead to a health disorder called Piriformis Syndrome. In this paper, we use an intelligent office chair in order to detect the wallet usage as a 'bad sitting posture', as sitting on a wallet can create an uneven sitting surface, subsequently tilting the pelvis in the frontal plane. The system is comprised of a pneumatic circuit and is able to detect and classify, based on Artificial Neural Network, 12 standardized sitting postures, with an accuracy of 80.9%. In this test, we asked 36 subjects (24 males-M and 12 females-F) to wear a wallet in the back pocket in 12 testing levels, based on 3 wallets sizes (small, medium and large) and 4 levels of wallet heights (no paper cards, 8 cards, 16 cards and 24 cards). We detected the usage of wallets as an incorrect posture in 58.8% for all levels (61.1% for Male and 54.2% for Female). We observed that the size of the wallet did not alter results significantly (60.4% for smaller area versus 57.6% in the larger area), while the wallet height had a large influence (46.2% for no cards versus 71.3% for 24 cards). We also tested wallet usage in the front pocket with an average of 16.7%, showing that this usage doesn't alter significantly the sitting posture. This work shows that the creation of an alert protocol for the wallet usage is possible to be implemented in our intelligent chair system.

Original languageEnglish
Title of host publicationENBENG 2017 - 5th Portuguese Meeting on Bioengineering, Proceedings
EditorsP. M. Afonso, M. Amador, M. Morgado, R. Bernardes
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)978-150904801-4
Publication statusPublished - 29 Mar 2017
Event5th Portuguese Meeting on Bioengineering, ENBENG 2017 - Coimbra, Portugal
Duration: 16 Feb 201718 Feb 2017


Conference5th Portuguese Meeting on Bioengineering, ENBENG 2017


  • Neural networks

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