Development of Techniques for Measuring Lower Limb Flexibility in the Elderly
Authors: Feng Bingbing , Zhao Yulin 
Published: January 2025

Flexibility as one of the influencing factors of physical fitness, is an essential component of overall health and can be regulated through muscle control and joint range of motion.However, the range of motion of many joints tends to decrease with age.The research suggests that, irrespective of gender, shoulder flexibility decreases by approximately 10% per decade from the age of 65. While some individuals maintain their flexibility as they age, their joint function range remains significantly less than that of younger individuals. The decline in joint flexibility directly contributes to reduced physical and functional capabilities, potentially impacting the independence and quality of life for older adults. Therefore, maintaining flexibility is crucial for the elderly population.However, the presence of the body's compensatory mechanism often complicates the detection of a decline in flexibility, leading to limitations in regular individual measurements. Mainstream methods for assessing flexibility primarily involve conventional physical fitness testing techniques and relevant range-of-motion evaluation tools. Common techniques for measuring flexibility mainly encompass the use of contact and non-contact measurement tools such as rulers, goniometers, inclinometers, etc., which quantify range of motion numerically. These methods are well-established in terms of technical principles and offer relatively low costs. Non-contact measurement includes two-dimensional image-based body measurement technology, three-dimensional body measurement technology, and 4D scanning technology. Two-dimensional body measurement relies solely on subject image information but has drawbacks such as difficulty verifying measurement errors. Three-dimensional human body measurement technology is widely used in fields like fashion industry, industrial design, medicine, and gaming due to its relatively accurate data; however high venue requirements and equipment costs hinder its widespread application in daily scenarios.Therefore, this study takes the flexibility of the lower limbs of the elderly as an example, and will develop a new flexibility measurement technique through the construction of a flexibility measurement unit, the determination of the measurement base, and the establishment of the measurement method.To develop a flexible measurement technique, this study centers around four processes: concept definition, method creation, technology selection, and tool design. In terms of conceptual definition, it is proposed to use the ratio method to establish a mathematical formula for flexibility measurement by taking into account the internal factors affecting flexibility in the elderly, and to improve the concept of flexibility measurement, redefine the time and frequency of measurement, and redefine a scientific unit of flexibility measurement. In terms of method creation, it is hoped that the location of key skeletal points in the human body can be deduced from the characteristics of the human body surface, to build a personalized human skeletal structure and accurately measure external joint activity. In terms of technology selection, we comprehensively compare the application of non-contact measurement technology and contact measurement technology, explore the new direction of traditional technology development, and look for breakthroughs in the application of technological innovation; in terms of tool design, we utilize the mirror theory to turn complaints into wishes, explore creative solutions, and design a new type of measurement tool to be used with the mobile phone application of data logging and data display, to measure human body's flexibility in all dimensions, Through the design of new measurement tools, together with data recording and data display mobile applications, we can measure human flexibility in all directions and multiple dimensions, build a visualization platform for flexibility data, accumulate and count the flexibility data in the long term, and help improve the construction of the flexibility database.This study will fill the gap of human factors engineering in the methodological dimension of flexibility measurement, and develop a new lower limb flexibility measurement technology for the elderly, which will not only provide data support for the development of the elderly health industry, but also open up business opportunities for the industry, and innovate the technology system and commercial service model.