Three-dimensional surfaces for human muscle kinetics.

Torque, angular velocity and angular position data were collected on six subjects performing maximum knee extensions at 11 speeds. Three-dimensional (3-D) surfaces were drawn for each subject and for the normalised, averaged data. For each subject, the moment arms of knee extensor and patella excursion were determined from radiographs and averaged across subjects. These data were then used to convert the angular data to linear force, velocity and information on muscle length. Surfaces were plotted for these data and evaluated. Results indicate a major difference between the knee positions for production of peak force or torque. Peak linear force was found to occur at an average of 75 degrees of flexion, while peak torque was found at 57 degrees. It was also suggested that 3-D surfaces provide more information than the traditional methods of presenting dynamic strength results.