Journal of Martial Arts Anthropology

Abstract - Autocorrelation in the analysis of a stochastic process of athletes and students

Background. It was assumed that an indirect evaluation of motor control processes could be conducted on the basis of autocorrelation function computed from time series. The time series were computed from the values of changes of the ground reaction force during maintaining balance in the upright standing position. The researchers deliberately selected a process of standing in the upright position since it is a permanent act of movement.
Aim. This research aimed to determine correlations occurring between the right and left limb in balancing ground reaction forces while maintaining an upright body position. The correlations were computed on the basis of the autocorrelation function (zero of a function). The study was conducted on track and field athletes, football players and students.
Methods. The study comprised of taking measurements and recording ground reaction forces while maintaining balance in the upright standing position. The measurement process lasted 15 seconds and was repeated three times. Changes of ground reaction forces attained from two independent Kistler plates were recorded as time series. The recordings were synchronized in time. Values of force components recorded during the testing were used to draw autocorrelation function. The function was adopted to determine time needed by the autocorrelation function to reach 0.
Results. Differences observed in the examined groups showed statistical significant differences in the lateral force direction. There were also statistically significant differences in the values of horizontal force components of pressure exerted by the left and right foot. Analysis of mean values of time needed by the function to reach 0 for the lateral force component indicated that time needed by the track and field athletes was the longest for both feet. Statistically significant differences in values of the football players were observed between the right and left foot but only in the lateral force.
Conclusions. The study revealed that the students displayed the least control over balancing ground reaction force in a vertical position. All groups attained statistically significant differences in balancing force pressure on a surface exerted by the right and left foot for vertical force components. Values computed for the group of students were random. There were no statistically significant differences observed between the right and left foot in the athletes. While, statistically significant differences in the football players’ values were observed between the right and left foot, this applied only for the lateral force.