Effective force application in guided leg extensions

In guided movements, limb kinematics is determined by the object on which a force is applied (as in cycling). Consequently, the force direction may deviate from the effective direction. It is examined how effective force application is related to maximal power output. A recent study, where subjects performed guided leg tasks on a special dynamometer, showed that maximal power output can be achieved with a low force effectiveness. To reveal the background of this phenomenon, the kinematics of one of these tasks is used in a simulation model. The stimulation level of six leg muscles was optimized towards a maximal effective force component with and without a constraint on the direction of the total force. Additionally, experiments were done to validate the simulation results. Both simulation and experiments showed that the muscle pattern with the highest effective force coincided with a low force effectiveness. Apparently, this is a prerequisite for maximal power transfer from the muscles to the plate in these guided movements.