Contents I. Introduction
Weakened muscle strength of lower extremity in elderly individuals increases the risk of falling, reduces walking ability, and may lead to lower quality of life. Therefore, early assessment and prevention of muscle weakness are important. Currently, in clinical practice, measurements are performed by specialists using dynamotors and other devices. However, these devices are large and expensive, thus it is difficult to use in daily life. Therefore, in some previous studies relation between standing and gait movement and lower extremity strength was analyzed to create simpler methods for evaluating lower extremity strength. For example, some previous studies have used the five-times sit-to-stand test to determine balance ability, risk of falling, and lower extremity strength [1]-[3] and examined the correlation between maximum walking speed and lower extremity strength [4]. Other studies have also shown relation between gait movement on a path with obstacles at maximum velocity and lower extremity strength [5],[6]. However, these methods require the participants to move at maximum speed, which can be burden for elderly individuals and leads to safety issues. Further, in these studies, the correlation coefficient between gait movement and lower extremity strength were approximately 0.4–0.6, which may be not enough for estimating lower extremity strength. In addition, models for estimating lower extremity strength using multiple parameters have not been constructed.
