Effect of reserve actuator for muscle force estimation using OpenSim

The reserve actuators used in the optimization calculation of the musculoskeletal software OpenSim apply reserve torques to the rotational movement of each joint. In this study, we verify range of reserve actuator settings that can appropriately estimate muscle forces. Seven healthy adult men walk during the experiment. The results of the estimated lower limb muscle forces during walking and the reserve torques indicate that the biarticular muscles, including rectus femoris and biceps femoris long head, and the monoarticular muscles which have many muscle attachment points, including gluteus maximus and psoas muscles, are not affected by the reserve actuators. While soleus muscle, gastrocnemius muscle, tibialis anterior muscle, and biceps femoris short head, which have few muscle attachment points are easily affected by the reserve actuators.