3D analysis system for estimating intersegmental forces and moments exerted on human lower limbs during walking motion

• Evaluating the intersegmental forces/moments without the need for force plates.
• Considering a 3D walking motion in the analytical model.
• Deriving the intersegmental forces/moments based only on the kinematic data.
• Measuring the kinematic data by inertial measurement units.
• Confirming the analytical results by comparing with the experimental data.

The intersegmental forces and moments acting on the human lower limbs during walking are generally estimated by applying an inverse dynamics approach to the ground reaction force (GRF) acting on the feet. The GRF data is obtained either directly using force plates or by means of a curve-fitting technique based on experimental samples. However, force plates are inconvenient and expensive, while curve fitting is unreliable since significant variations may exist in the GRF among different individuals. Accordingly, the present study proposes a method for evaluating the intersegmental forces and moments acting on the lower limbs based solely on the posture information obtained from seven inertial measurement units (IMUs) placed on the lower limbs and trunk and a 3D analytical model of the human walking motion. The results obtained from the analytical model for the forces acting on the phalange and heel are compared with the experimental data obtained using load cells. It is found that a good agreement exists between the two sets of results. Thus, the basic validity of the proposed analysis system is confirmed.