| The purpose of the research was to extend the fundamental contributions by Troxell (1982) on the Interactive Variable Resistance Exercise (IVRE) approach to maximizing force output. The testing apparatus was a Smith machine modified for pneumatic resistance and equipped with pressure, position, and velocity transducers. The resistance level varied interactively with the user based on velocity to accommodate for changing biomechanics.; The squat exercise is a multijoint lift that does not have a universal force profile. Mechanical means such as a cam may not be used to match the changing strength capacity throughout the range of motion (ROM). Therefore, this exercise requires another method such as the IVRE approach to vary the resistance for maximizing the force output through the ROM.; A study was conducted in which the isometric strength profile was experimentally determined. The lowest force on the strength curve illustrated the Isometric Sticking Region Force (ISRF). Also, the linear Force-Velocity (F-V) curve for each subject was determined experimentally. The intercept of the force axis at zero velocity is the theoretical maximum force, F0. The F-V curve was used to set the desired velocity, VD, by which the resistance level varied on the IVRE lifts. During IVRE if the participant's instantaneous resultant velocity, VR, exceeded VD, then the resistance was increased. Thus at maximal exertion a higher velocity indicates more strength capacity, and the resistance level increased accordingly.; Contributions are delineated into machine development and human subject testing results. The research accomplished its objective of developing and verifying an IVRE apparatus capable of providing isometric, constant, and variable resistances as well as collecting data for select parameters. Human testing results revealed that the ISRF occurs at the 90° knee angle, and the ISRF corresponds to approximately 50% of F0. Thus the ISRF may be used to predict F0 permitting dynamic strength to be assessed with a single isometric exertion, and future IVRE research can utilize the F-V curve used to select an initial resistance level and the VD. |
