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

Abstract

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.

Modelling the joint torques and loadings during squatting at the Smith machine

“…If the latter is an opportunity or a limitation is unclear, since different elements interacting with each other should be taken into account: external load, foot positions, degree of forward/backward trunk tilt relative to the vertical, hip and knee angles. Although previous studies in which the Smith squat was used focused on testing issues (Cotterman, Darby, & Skelly, 2005;Harris, Cronin, & Hopkins, 2007;Paulus, Reiser, & Troxell, 2008;Thomas et al, 2007) and various training aspects (Harris, Cronin, Hopkins, & Hansen, 2008;McGuigan, Chiagiarelli, & Tod, 2005;Minahan & Wood, 2008;Vingren et al, 2008), no study, to our knowledge, has specifically examined the joint torques and joint loads (shear and compressive joint reaction forces) that occur during the execution of this exercise. Moreover, in the fields of athletic training, fitness, and rehabilitation, the debate continues between those who believe the Smith machine exercise could be dangerous because the path is unnatural and the machine prevents the body from determining its natural movement, and those who consider this exercise even safer and more effective than the standard barbell squat (Griffing, 2010).…”

Joint Torques and Joint Reaction Forces During Squatting With a Forward or Backward Inclined Smith Machine

“…Typically, the joint torques and loadings are increased (decreased) at the beginning (end) of the concentric phase and at the end (beginning) of the eccentric phase of the exercise. 37,38 However, these effects can be quantified only on a case-by-case basis, and do not affect the general trends set by the equipment inclination (Figures 3-8), which are the subject of this article.…”

Measurement of Power in Selectorized Strength-Training Equipment

“…This latter setting, typically implemented in commercial equipment, can return unreliable data in explosive movements with low resistances. In fact, during these kinds of exercises, the selected weight stack typically reaches high velocity and, consequently, the cable could lose its tension during the joint deceleration phase, and the weight stack could continue to rise along the vertical even before the end of the concentric phase (  u = 0) of the joint movement (see, for example, Paulus et al, 2008). This effect is progressively minimized by designing the pulley system with more and more advantageous lever efficiency (2:1, 4:1, and so on).…”