Kinetics of the parallel squat
McLaughlin, T.M.; Lardner, T.J.; Dillman, C.J.
Research Quarterly 49(2): 175-189
1978
ISSN/ISBN: 0034-5377 PMID: 725284 Document Number: 4291
This study investigated the muscular torques and joint forces during the parallel squat, as performed by some of the best national and world-class powerlifters. Cinematographic analysis of 12 competitors in the U.S. Senior National A.A.U. Powerlifting Championships provided continuous measurements of joint and bar centers. These data were used in dynamic equations of motion to obtain vertical and horizontal joint forces and muscular torques for the shank, thigh, and trunk. Prior to analysis, subjects were further classified into three groups according to skill shown in performing the parallel squat. Results indicated that high-skilled subjects minimized trunk torques by maintaining a more erect trunk position and also demonstrated more extensor-dominant thigh torques. It was also found that quasistatic or static treatments of the parallel squat provide results within 10% of the dynamic equations of motion. The following conclusions can be drawn from this study: 1. Although most sources indicate the parallel squat to be primarily a leg-extensor activity, the results of this study show that trunk extensors play a significant role. Across a wide range of trunk-angle positions, the muscular torques for the trunk extensors were substantially greater than the thigh and shank torques. The degree of forward lean during the lift appears to increase the torque for the trunk extensors and reduce those of the thigh extensors. Practitioners and others using the parallel squat primarily for quadriceps development would be well advised to consider the position of the trunk during its execution. Individuals with excessively weak or injured trunk extensors should be similarly cautioned. 2. High-skilled subjects clearly attempt to minimize trunk torques in order to improve performance and do so primarily by maintaining a more erect trunk position. This action results in more extensor-dominant thigh torques during performance of the parallel squat. 3. There was little difference in the results for muscular torques and joint forces when static or quasistatic conditions were used instead of the dynamic equations of motion. Future investigations of the parallel squat can obtain reasonable results with these simpler methods and need not resort to more complex dynamic analyses.
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