title: Modelling the joint torques and loadings during squatting at the Smith machine.
abstract: An analytical biomechanical model was developed to establish the relevant properties of the Smith squat exercise, and the main differences from the free barbell squat. The Smith squat may be largely patterned to modulate the distributions of muscle activities and joint loadings. For a given value of the included knee angle (θ(knee)), bending the trunk forward, moving the feet forward in front of the knees, and displacing the weight distribution towards the forefoot emphasizes hip and lumbosacral torques, while also reducing knee torque and compressive tibiofemoral and patellofemoral forces (and vice versa). The tibiofemoral shear force φ(t) displays more complex trends that strongly depend on θ(knee). Notably, for 180° ≥ θ(knee) ≥ 130°, φ(t) and cruciate ligament strain forces can be suppressed by selecting proper pairs of ankle and hip angles. Loading of the posterior cruciate ligament increases (decreases) in the range 180° ≥ θ(knee) ≥ 150° (θ(knee) ≤ 130°) with knee extension, bending the trunk forward, and moving the feet forward in front of the knees. In the range 150° > θ(knee) > 130°, the behaviour changes depending on the foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are explained. This work enables careful use of the Smith squat in strengthening and rehabilitation programmes.
authors.affiliation: Department of Surgical, Radiological and Odontostomatologic Sciences, Medical Physics Section, University of Perugia, Perugia, Italy. biscarini@fisica.unipg.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Biscarini
authors.forename: Paolo
authors.initials: P
authors.lastname: Benvenuti
authors.forename: Fabio
authors.initials: F
authors.lastname: Botti
authors.forename: Francesco
authors.initials: F
authors.lastname: Mastrandrea
authors.forename: Silvano
authors.initials: S
authors.lastname: Zanuso
mesh_terms: D016118:Anterior Cruciate Ligament; D015444:Exercise; D006801:Humans; D007717:Knee; D007719:Knee Joint; D035002:Lower Extremity; D008954:Models, Biological; D016119:Posterior Cruciate Ligament; D011187:Posture; D019876:Sports Equipment; D013314:Stress, Mechanical; D019415:Torque; D014891:Weight Lifting; D016474:Weight-Bearing