PNF and Movement 2021; 19(3): 375-382
https://doi.org/10.21598/JKPNFA.2021.19.3.375
Effects of the Air-Pressure Asymmetry of Wheelchair Tires on Pelvic Height, Gluteal Pressure, and Muscular Recruitment Pattern in Asymptomatic Participants
Sang-Yeong Park, P.T., Ph.D.⋅Se-Yeon Park, P.T., Ph.D.
Department of Physical Therapy, Uiduk University
Correspondence to: Se-Yeon Park (arclain@naver.com)
Received: October 28, 2021; Revised: November 8, 2021; Accepted: November 9, 2021; Published online: December 31, 2021.
© Korea Proprioceptive Neuromuscular Facilitation Association. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose: The objectives of the present study were to investigate the disadvantages of tire pressure asymmetry of a wheelchair tire and recommend the criterion for appropriate tire pressure without generating negative changes in the musculoskeletal system in asymptomatic participants.
Methods: Fourteen asymptomatic participants were asked to sit in pressure-controlled wheelchairs and perform desk work for 20 minutes in each tire condition. The asymmetry of the tire conditions was set as 0% difference, 25% difference, and 50% difference from the recommended pressure. The pelvic alignment and muscular recruitment represented as a flexion-relaxation ratio (FRR) were measured at pre-test, and after each condition of desk work. The displacement of the center of pressure (COP) was measured during the desk work.
Results: The tire air pressure condition significantly affected the FRR and COP (P < 0.05). Both sides of the FRR values were significantly higher under the symmetrical tire conditions (0% difference) and pre-test, compared with the asymmetrical tire condition of 50% difference (P < 0.05). The mediolateral COP displacement of the asymmetrical tire conditions (25% and 50% difference) was significantly higher than that of the symmetrical tire conditions (0%) (P < 0.05).
Conclusion: Asymmetrical tire conditions could cause changes in the muscle recruitment pattern of the erector spine and mediolateral COP displacement. Tire pressure asymmetry higher than 50% could be a risk factor for prevalence of back pain, so this level of asymmetry in tire pressures should be cautioned against for wheelchair users.
Keywords: Center of pressure, Flexion-relaxation ratio, Neuromuscular


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