title: Rotated balance in humans due to repetitive rotational movement.
abstract: We show how asymmetries in the movement patterns during the process of regaining balance after perturbation from quiet stance can be modeled by a set of coupled vector fields for the derivative with respect to time of the angles between the resultant ground reaction forces and the vertical in the anteroposterior and mediolateral directions. In our model, which is an adaption of the model of Stirling and Zakynthinaki (2004), the critical curve, defining the set of maximum angles one can lean to and still correct to regain balance, can be rotated and skewed so as to model the effects of a repetitive training of a rotational movement pattern. For the purposes of our study a rotation and a skew matrix is applied to the critical curve of the model. We present here a linear stability analysis of the modified model, as well as a fit of the model to experimental data of two characteristic "asymmetric" elite athletes and to a "symmetric" elite athlete for comparison. The new adapted model has many uses not just in sport but also in rehabilitation, as many work place injuries are caused by excessive repetition of unaligned and rotational movement patterns.
authors.affiliation: Instituto de Ciencias Matemáticas, CSIC-UAM-UC3M-UCM, c/ Serrano 121, 28006 Madrid, Spain.
authors.forename: M S
authors.initials: MS
authors.lastname: Zakynthinaki
authors.forename: J Madera
authors.initials: JM
authors.lastname: Milla
authors.forename: A López Diaz
authors.initials: AL
authors.lastname: De Durana
authors.forename: C A Cordente
authors.initials: CA
authors.lastname: Martínez
authors.forename: G Rodríguez
authors.initials: GR
authors.lastname: Romo
authors.forename: M Sillero
authors.initials: MS
authors.lastname: Quintana
authors.forename: J Sampedro
authors.initials: JS
authors.lastname: Molinuevo
mesh_terms: D000465:Algorithms; D056352:Athletes; D006801:Humans; D016014:Linear Models; D016139:Martial Arts; D008953:Models, Anatomic; D015233:Models, Statistical; D009068:Movement; D017711:Nonlinear Dynamics; D004856:Postural Balance; D012399:Rotation