Development of a Prototype Device for Guiding Accurate 7-Count Quadriceps Strengthening Exercises Using Visual Feedback

Abstract

Quadriceps strengthening exercise plays an important role in maintaining physical fitness and preventing knee joint injury, particularly in elderly. However, inadequate control of movement angle and exercise tempo may increase the risk of injury. This study therefore aimed to (1) design and develop a prototype device, "QUAD-Guide," to assist users in performing the seven-count quadriceps strengthening exercise with improved accuracy through visual guidance, (2) apply principles of physics and mathematics to determine the optimal movement angle, and (3) conduct a preliminary functional test of the prototype in terms of angle and tempo control. This study employed a preliminary experimental design using two sample groups. Group 1 consisted of 25 participants aged 40–50 years, selected by purposive sampling, for physical data collection to inform device design. Group 2 consisted of 4 volunteers, selected by convenience sampling, for preliminary device testing. Research instruments included the QUAD-Guide prototype, a goniometer for measuring leg-raise angle, and a stopwatch for recording movement time. Data were analyzed using descriptive statistics including mean, minimum, maximum, and standard deviation, and the Wilcoxon Signed-Rank Test was used to compare differences between device-assisted and unassisted conditions at a significance level of 0.05. Results indicated that the use of QUAD-Guide significantly improved users' ability to control leg-raise angle accuracy. The mean angular deviation decreased from 11.6 degrees to 3.7 degrees, representing a statistically significant reduction of approximately 68.1%. The mean time required to raise the leg to the target height also decreased from 1.8 seconds to 0.6 seconds, reflecting a statistically significant improvement of approximately 66.7%. These findings suggest that the QUAD-Guide prototype has potential for promoting exercise, and may serve as a foundation for future development of community-based health-supportive devices. However, future research should expand the sample size, conduct testing in older adult populations, and perform systematic instrument quality verification to confirm the device's effectiveness prior to practical implementation.