The objective of this study was to develop a method to estimate thigh-calf contact force during heel-rise squatting posture, which is important for analyzing the kinetics of the lower limb during deep knee flexion; however, the measured forces varied widely among test subjects. We also considered joint angles, rather than only individual anthropometric, such as height, body weight (BW), or body mass index (BMI). We created estimation equations by a linear combination of both physical and posture parameters, and then performed the measurement experiment with 10 healthy males. Test subjects were asked to take a squatting posture, and to bend their upper bodies forward and backward. We measured thigh-calf contact force by placing a pressure distribution sensor sheet between the thigh and calf. At the same time, the joint angles were measured as estimation parameters. Coefficients of the estimating equations were determined to minimize the root mean square error of the estimated and measured values. We compared four estimation equations, using physical and posture parameters, as well as those selected from all parameters, which are easily measurable. As a result, the estimation accuracy improved by using both physical and posture parameters. The average magnitude of the thigh-calf contact force was 0.92±0.24BW, and the average error of estimation was 0.06BW. The error was 0.11BW by using only physical parameters, and was 0.15BW by using only posture parameters. Despite this, even the estimation error using selected parameters was 0.07BW, while the maximum error was 0.25BW. We confirmed that there was little posture change adversely affecting thigh-calf contact force. Individual anthropometric parameters were important for estimation, although we used similar subjects for gender, age, and physical size. In the future, we will be recruiting more test subjects and discussing the effect of physical parameters, not only anthropometric values.
2016 by The Japan Society of Mechanical Engineers