Relationship between force and velocity in isotonic knee extension exercise: A preliminary study for the selection of the maximum and minimum load

[Purpose] To demonstrate the relationship between force and velocity in isotonic contraction of knee extension, and with estimation of isometric peak torque, investigate the appropriate load for physical safety in human measurements. [Subjects] Six healthy males in their 20s and 30s. [Methods] Images captured by a high-speed video camera were converted to sequential frames using video editing software. Using the angle measurement tools of image measurement software, angular velocities, and knee angles were determined, and the angular velocities were compared among minimum loads of 20, 30, and 40% 1RM, and maximum loads of 100, 130, 150 and 160% 1RM. [Results] There were no significant differences among the three minimum loads, but there was a significant difference between the maximum loads of 150 and 160% 1RM. [Conclusion] We consider that a minimum load of 40% 1RM and a maximum load of 150% 1RM are appropriate loads.