Interactive variable resistance exercise system concept and preliminary results.

In order to maximize loading during resistance exercise, muscles should be heavily taxed throughout the entire range of motion for that exercise. Traditional constant resistance squats only tax the lower-extremity muscles to their limits at the "sticking region" or a critical joint configuration of the exercise cycle. Therefore, a Smith machine was modified for pneumatic resistance with appropriate computer control so that it is capable of adjusting force within a repetition of the squat exercise. The control program was designed to increase the loading after accelerating to a specified lifting velocity which indicates increased strength capacity from being past the sticking region. Human subject testing showed the percent increase from initial to final resistance level normalized by body and barbell weight was an average of 14% (+/-5%) for men and 29% (+/-14%) for women with both separately showing a significant increase in resistance level (p>0.00005 each). The men had significantly higher initial (p=0.007) and final (p=0.04) normalized resistance levels than the women. This investigation indicates that interactive variable resistance exercise is capable of significantly increasing the loading after a desired instantaneous velocity is reached; however, further performance testing is required to determine its efficacy.

Peak lifting velocities of men and women for the reduced inertia squat exercise using force control.

The purpose of the research was to determine peak velocities for the reduced inertia squat exercise at various resistance levels based on an isometric strength assessment for both men and women. On a Smith machine modified for pneumatic resistance, 12 males and 12 females previously trained college-age participants performed a maximal isometric strength assessment with knee angles of 90 degrees , 110 degrees , 130 degrees , 150 degrees and 170 degrees (180 degrees = full extension) followed by dynamic maximal effort squats with resistance maintained at 40, 50, 60, 70, and 80% of their lowest maximum isometric strength. No interaction existed between the men and women during isometric strength tests with the men stronger in every joint position (P < 0.05). The lowest isometric strength occurred at 90 degrees without variation. There was an interaction between men and women for peak lifting velocity during the dynamic lifts (P = 0.021) with the men producing higher velocities at all levels of resistance (P < 0.05). The difference in peak velocity between the sexes was greatest at the lowest resistance level and that difference was less significant at the higher resistance levels. The relationship between resistance force and peak lifting velocity is applicable to increasing the efficiency of the squat by maximizing force output per repetition by varying the resistance as the lifter approaches peak velocity similar to isokinetics with preloading and active instead of reactive resistance.

Pneumatic strength assessment device: design and isometric measurement.

In order to load a muscle optimally during resistance exercise, it should be heavily taxed throughout the entire range of motion for that exercise. However, traditional constant resistance squats only tax the lower-extremity muscles to their limits at the "sticking region" or a critical joint configuration of the exercise cycle. Therefore, a linear motion (Smith) exercise machine was modified with pneumatics and appropriate computer control so that it could be capable of adjusting force to control velocity within a repetition of the squat exercise or other exercise performed with the device. Prior to application of this device in a dynamic squat setting, the maximum voluntary isometric force (MVIF) produced over a spectrum of knee angles is needed. This would reveal the sticking region and overall variation in strength capacity. Five incremental knee angles (90, 110, 130, 150, and 170 degrees, where 180 degrees defined full extension) were examined. After obtaining university-approved informed consent, 12 men and 12 women participated in the study. The knee angle was set, and the pneumatic cylinder was pressurized such that the subject could move the barbell slightly but no more than two-centimeters. The peak pressure exerted over a five-second maximum effort interval was recorded at each knee angle in random order and then repeated. The average of both efforts was then utilized for further analysis. The sticking region occurred consistently at a 90 degrees knee angle, however, the maximum force produced varied between 110 degrees and 170 degrees with the greatest frequency at 150 degrees for both men and women. The percent difference between the maximum and minimum MVIF was 46% for men and 57% for women.