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This paper discusses the major assumptions of influential ecological approaches on the human movement variability in sports and how it can be analyzed by benefiting from well-known measures of entropy. These measures are exploited so as to further understand the performance of athletes from a dynamical and chaotic perspective. Based on the presented evidences, entropy-based techniques will be considered to measure, analyze and evaluate the human performance variability under three different case studies: i) golf; ii) tennis; and iii) soccer. At a first stage, the athletes' performance will be analyzed at the individual level by considering the golf putting (pendulum movement) and the tennis serve (ballistic movement). Under these gestures, the approximate entropy is considered to extract the variability inherent to the process variables. Afterwards, the athletes' performance will be analyzed at the collective level by considering the soccer case (team sport). To that end, OPEN ACCESS 2 both approximate entropy and Shannon's entropy are mutually considered to assess the variability of football players' trajectory. To outline the applicability of entropy-based measures to analyze sports, this article ends with an overall reflection about the potential of such measures towards an increased understanding on the overall human performance. This methodology proves to be useful to provide decisive information and feedback for coaches, sports analysts and even for the athletes.

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This study analysed the extrinsic constraint of induced aerodynamic flow (IAF) on the first serve by expert tennis players with temporal organization of the movement, as well as the velocity and amplitude of the racket motion analyzed. Twelve expert right-handed tennis players voluntarily participated in this study. Each player performed 20 trials without IAF and another 20 trials for each different speed configuration of induced cross-wind: 2.4 m/s; 4.3 m/s; 5.8 m/s; and random speed. The coefficient of variation, r-pearson test and the inferential test one-way ANOVA were used to compare movement data. The results suggest spatio-temporal adjustments depending on the wind speed. Moreover, statistical differences were identified on both the temporal organization of the serve and on the racket's motion amplitude and velocity. The intra- and inter-individual variability of the motor behavior shows the uniqueness of the serve movement of each player.