Training implications of maximal forces on a computer-controlled and motor-driven leg press by age group, sex, footplate direction, and speed

Abstract

Strength training that overloads lengthening muscle fibers may result in greater strength gains with less effort and perceived exertion than conventional training modalities. This study evaluates a device capable of this overloading (a motor-driven and computer-controlled leg press) to develop recommendations for future training interventions. Unimpaired younger and older men and women (7/group, total n=28) performed three maximal-effort trials for both directions of footplate motion (IN and OUT) at three speed profiles (knee rotation speeds of 15, 25, and 35°/s) on a motor-driven and computer-controlled leg press. Normalized forces were tested for effects of age group, sex, direction of footplate motion, and knee rotation speed. Peak forces were 57% greater for younger and 20% greater for IN. Trends of greater IN relative to OUT forces (IN overloading) were present in women, but this was due to an inverse correlation between strength and IN overloading that was independent of age group and sex. Leg press strength training on a device that is capable of overloading lengthening muscle fibers is a promising new training method that appears to have the greatest potential benefits for the weakest participants. Training target profiles on the device tested and others similar to it should be set based on participant-specific maximums across the ROM in both IN and OUT directions at a speed in the middle of the range to be trained.

Resistance Exercise Machine within Lower Body Negative Pressure for Counteracting Effects of Microgravity

“…The human strength curve for the leg-press exercise shows that the maximum force a user can produce at each point in the outward cycle gradually increases. Not surprisingly, we are able to generate far more force at the extreme position (when the knee joint is at full extension) than when the knee is sharply bent (Schulz et al, 2012). Mechanical work and effort in the muscles will be nearly optimized in relation to the muscle mechanics when the resistance provided by a machine most nearly matches this trend (Zwart et al, 2007).…”