Relationship between center of pressure and contact region during gait: implications for shoe wear and slipping risk Joseph Sukinik, Rosh Bharthi, Sarah Hemler, Kurt Beschorner Human Movement and Balance Laboratory, Department of Bioengineering Joseph Sukinik is a senior bioengineering student originally from North Bethesda, Maryland. He is interested in biomechanics and medical device development. He hopes to attend medical school in the future. Joseph Sukinik
Kurt Beschorner is an Associate Professor of Bioengineering at the University of Pittsburgh. He utilizes techniques in tribology, biomechanics and ergonomics to generate understanding and interventions for falling accidents. Kurt Beschorner, Ph.D.
Significance Statement
The shoe contact region is relevant to its friction and the shoe’s response to wear. This study aimed to determine if ground reaction forces could predict this region.
Category: Experimental Research
Keywords: COF, contact region, slip and fall accidents
94 Undergraduate Research at the Swanson School of Engineering
Abstract
One of the leading sources of occupational injuries, and injuries among the elderly, are slip and fall accidents. These accidents are initiated by a low coefficient of friction (COF) between the shoes and floor. Flooring and footwear products that offer good friction can improve safety and yield a competitive advantage for companies. As shoes become worn, the tread blocks degrade, reducing their friction capability and increasing slip risk. However, wear is uneven, and some parts remain completely intact. This study focuses on generating a method to guide shoe tread design and reduce slip risk through prediction of the contact region with ground reaction forces. Using force plates and a frustrated total internal reflection (FTIR) device embedded in the floor, we generated ground reaction force data and shoe contact images to measure center of pressure (COP) and the contact region centroid, respectively. The contact region (from FTIR) and COP (from the force plate) was quantified during the moment of maximum friction requirements. Correlation analysis was performed. Mediolateral COP was shown to have a strong correlation with the mediolateral centroid (r = 0.933, p < 0.001), while the anteroposterior COP showed a weak correlation to the anteroposterior centroid (r = 0.397, p = 0.115). This study provides rationale that the COP can be used to predict the contact region in the mediolateral direction. Results from this study can be used to expand this analysis to consider additional types of shoes and generalize this method of determining wear location on any footwear.
1. Introduction
Slip and fall accidents are a serious problem that plagues both occupational environments and the lives of the elderly. In general, falls (which are commonly caused by slipping) are defined as “an event which results in a person coming to rest unintentionally on the ground or other lower level, not as a result of a major intrinsic event (such as stroke) or overwhelming hazard” [1]. In 2012 alone, the Liberty Mutual Workplace Safety Index showed that the cost of disabling injuries due to falls in the workplace is around $9.19 billion and accounts for approximately 15% of total injury costs in the US [2]. While falls typically yield worse outcomes for elderly patients, falls occur at similar rates regardless of age [3, 4, 5]. One of the leading causes of falls is slip, which can occur as treads begin to wear on the shoes. According to Courtney et al. approximately 40-50% of all fall-related injuries involved slipperiness [6]. Additionally, Berg et al. found that among the elderly, approximately 59% of falls were due to slipping, and approximately 5% resulted in fractures, while an additional 9% caused significant soft tissue damage [7]. Lastly, previous work has shown good linearity between predicted contact pressures from contact mechanics and measured contact pressure from FTIR [8]. Thus, previous research studies show the potential of this technique to measure mechanics and demonstrate the need for increased research into tread design.
