Knee and elbow 3D strength surfaces: peak torque-angle-velocity relationships.

Recognizing the importance of both the torque-angle and torque-velocity relations, three-dimensional (3D) human strength capabilities (i.e., peak torque as a function of both joint angle and movement velocity) have been increasingly reported. It is not clear, however, the degree to which these surfaces vary between joints, particularly between joints with similar biomechanical configurations. Thus, our goal was to compare 3D strength surfaces between the muscles about the elbow and knee hinge joints in men and women. Peak isometric and isokinetic strength was assessed in 54 participants (30 men) using the Biodex System 3 isokinetic dynamometer. Normalized peak torque surfaces varied significantly between flexion and extension (within each joint) and between joints; however, the normalized 3D torque surfaces did not differ between men and women. These findings suggest the underlying joint biomechanics are the primary influences on these strength surface profiles. Therefore, in applications such as digital human modeling, torque-velocity-angle relationships for each joint and torque direction must be uniquely represented to most accurately estimate human strength capability.