Lower extremity forces and torques during systematic variation of non-weight bearing motion.

Component and resultant external forces and torques at ankle, knee, and hip joints of unrestrained lower extremity motion were computed as resultant limb velocities were systematically changed. Cinematographic and modeling techniques were used to analyze 45 trials of five skilled soccer players who performed slow, medium and fast velocity kicks. A model of the lower extremity was incorporated, with kinematic data and segment mass estimates, into computer programs to quantify the mechanical variables. Monotonic increases in magnitudes of all kinetic elements occurred as the velocity of kicking was increased. Significant differences were also observed in the maximum values of the net parallel and perpendicular external force actions, and resultant torques at the joints with changes in limb velocity.