title: An alternative approach to describing agility in sports through establishment of a relationship between velocity and radius of curvature.
abstract: Agility is an essential part of many athletic activities. Currently, agility drill duration is the sole criterion used for evaluation of agility performance. The relationship between drill duration and factors such as acceleration, deceleration and change of direction, however, has not been fully explored. This paper provides a mathematical description of the relationship between velocity and radius of curvatures in an agility drill through implementation of a power law (PL). Two groups of skilled and unskilled participants performed a cyclic forward/backward shuttle agility test. Kinematic data was recorded using motion capture system at a sampling rate of 200 Hz. The logarithmic relationship between tangential velocity and radius of curvature of participant trajectories in both groups was established using the PL. The slope of the regression line was found to be 0.26 and 0.36, for the skilled and unskilled groups, respectively. The magnitudes of regression line slope for both groups were approximately 0.3 which is close to the expected 1/3 value. Results are an indication of how the PL could be implemented in an agility drill thus opening the way for establishment of a more representative measure of agility performance instead of drill duration.
authors.affiliation: a Biomechanics and Sports Engineering Group, Biomedical Engineering Faculty , Amirkabir University of Technology , Tehran , Islamic Republic of Iran.
authors.forename: Ahmed Reza
authors.initials: AR
authors.lastname: Arshi
authors.forename: Hoda
authors.initials: H
authors.lastname: Nabavi
authors.forename: Sina
authors.initials: S
authors.lastname: Mehdizadeh
authors.forename: Keith
authors.initials: K
authors.lastname: Davids
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena; D006801:Humans; D008962:Models, Theoretical; D009048:Motor Skills / Q000502:physiology*; D009068:Movement; D013996:Time and Motion Studies; D055815:Young Adult
keywords: agility; motion analysis; power law; radius of curvature