A Novel Two-Velocity Method for Elaborate Isokinetic Testing of Knee Extensors

Abstract

Single outcomes of standard isokinetic dynamometry tests do not discern between various muscle mechanical capacities. In this study, we aimed to (1) evaluate the shape and strength of the force-velocity relationship of knee extensors, as observed in isokinetic tests conducted at a wide range of angular velocities, and (2) explore the concurrent validity of a simple 2-velocity method. Thirteen physically active females were tested for both the peak and averaged knee extensor concentric force exerted at the angular velocities of 30 degrees-240 degrees/s recorded in the 90 degrees-170 degrees range of knee extension. The results revealed strong (0.960 lt R lt 0.998) linear force-velocity relationships that depict the maximum muscle force (i.e. the force-intercept), velocity (velocity-intercept), and power (their product). Moreover, the line drawn through only the 60 degrees and 180 degrees/s data (the 2-velocity method') revealed a high level of agreement with the force-velocity relationship obtained (0.76 lt R lt 0.97; all power lt 0.001); while the force-intercept highly correlated (0.68 lt R lt 0.84; all power0.01) with the directly measured isometric force. The 2-velocity method could therefore be developed into a standard method for isokinetic testing of mechanical capacities of knee extensors and, if supported by further research, other muscles. This brief and fatigue-free testing procedure could discern between muscle force, velocity, and power-producing capacities.