title: The role of interaction torque and muscle torque in the control of downward squatting.
abstract: [Purpose] The purposes of this study were first to analyze the multijoint dynamics of downward squatting, and to examine the contribution of interaction torque and muscle torque to net torque, and second, to examine mechanisms of movement control. [Subjects] The subjects were 31 healthy men with a mean age of 21.0 ± 1.2 years (range, 19-24 years). [Methods] Squatting tasks with the trunk in two positions, an erect and anterior tilt position, were performed by the subjects. Net, interaction, muscle, and gravity torque were calculated according to the Lagrange equation using 3D tracking data. [Results] The contribution ratio of interaction torque to net torque was approximately 90%, irrespective of the joint and task. In contrast, muscle torque showed complicated behavior to compensate for gravity torque. A combined muscle and gravity torque profile showed flexion or dorsiflexion immediately after the initiation of the movement, and it later changed to extension or plantar flexion. [Conclusion] The torque that contributes almost exclusively to the net torque was interaction torque. The combination of muscle and gravity torque at the knee joint and the hip joint is important for movement control, independent of the starting position.
authors.affiliation: Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fujisawa
authors.affiliation: Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Murakami
authors.affiliation: Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kawakami
authors.affiliation: Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
keywords: Interaction torque; Motor control; Squatting