ANNALS OF APPLIED SPORT SCIENCE–Special Issue
First National Congress of
"New Scientific Consequence for Iran’s Sport Development" Lahijan Branch, Islamic Azad University, 2014, 10-11 December
w w w . aas s j our nal. c om
ISSN (Online): 2322 – 4479
Roundhouse Kick’s Variability in Kinematic
Coupling Assessed by Continuous Relative Phase and Vector Coding in Elite Taekwondo Players
1Kamran Azma, 2Hamid Reza Barnamei∗
1. Department of Medicine and rehibiliation, AJA University, Tehran, Iran.
2. Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran. University, Tehran, Iran.
Taekwondo techniques are inherently variable. A traditional perspective from Shannon’s
information theory (Shannon, 1948) argues that variability is synonymous with ‘‘noise’’ arising from errors, either in the performance of the movement or in the recording and treatment of the data (Fitts, 1954; Schmidt et al., 1979). Alternatively, dynamical systems theory argues that variability is not inherently good or bad, but reflects the variety of coordination patterns used to complete the task (Haken et al., 1985; Scho ̈ner and Kelso, 1988).
Researchers have used different techniques of nonlinear dynamics to study the structure of variability in sports movement. The two most popular techniques for quantifying variability in human movement appear to be vector coding (Heiderscheit et al., 2002; Ferber et al., 2005; Wilson et al., 2008) and continuous relative phase (CRP) (Hamill et al., 1999; Irwin and Kerwin,
2007; Miller et al., 2008). Although both techniques involve the assessment of coordination by the quantification of phase plane trajectories, the phase planes constructed with these two techniques are fundamentally different. The vector coding phase plane contains only spatial information derived from positional signals, while the CRP phase plane contains both position and velocity signals, and provides spatiotemporal information. In light of these differences, there is no assurance that vector coding and CRP convey similar information on the structure of variability when they are used to study a particular movement. In addition, a direct comparison between variability quantified by vector coding and by CRP has not been widely demonstrated in the biomechanics and motor control literature. Consequently, it is difficult to make comparisons between studies that use vector coding and those that use CRP. These comparisons are important if both techniques are to be used as measures of variability. Therefore, the purposes of the study
Hamid Reza Barnamei