Numerous motor-perceptual tasks can be observed across the ages, especially if individuals are involved in sport activities. A person facing a novel task has to elaborate new movements to achieve the task goal (skill acquisition period). To become more successful and efficient, that is, to be an expert in a learned task, the subject must adjusts movement parameters depending on many constraints (fine tuning skill period). From a Dynamic System Theory perspective, movement arises from the relative impact of practice and constraints (organismic, task, and environmental). Focusing in the organismic constraints, the a-priory talent is a critical point for understanding motor learning in the skill acquisition period. In addition, the age of the performer must be specially considered in the fine tuning skill period due to the biological maturational and expertise processes taking place with time. The overarching goal of this thesis was to characterize both periods of learning (skill acquisition and fine tuning process) from a dynamical system theory perspective focusing in the longswing as a sport skill. We observed that skill level (a-priori talent) can affect the learning process when a person faces a novel task. While swing amplitude is not impacted by the initial skill level, perceptual and motor learning (performance and coordination) in the downswing have larger improvements when initial skill level is closer to expert values. We proposed that flexion events' placement (P3H, P3S) and time lag between hip flexion and shoulder flexion actions during upswing (P3H-P3S) are critical in biomechanical terms, but coordination mode of the extension actions (P2H, P2S) is critical to increase swing amplitude in coordinative terms. Focusing in the fine tuning skill, our research showed that competition age groups swing amplitude was similar from G3 (12.88±0.50 years) to G5 (19.96±3.37 years). However, events are acquired progressively (from G3 to G5) in agreement with their spatial-temporal performance sequence. In contrast, our results only differentiated coordination modes of the beginners (G1, 8.92±0.85 years) and experts (G5). Interestingly, we observed increased changes in the within subject variability in G4 (14.78±0.57 years) suggesting a transition point. It was suggested that this transition point could be due to increased demands of the sport (learning flight elements, dismounts). These changes in variability mainly occurred in P3 variables (i.e. flexion actions during upswing). We proposed that interventions should be focused in P3 to acquire expert motor strategies. Finally, we proposed a conceptual model to understand the longswing learning process and to improve the intervention of the practitioners. Our results indicated that spatial-temporal sequences of the longswing actions appear to be learned before their dynamic control. In addition, adequate coordination of the previous action conditioned learning of the subsequent action. Decreases in the within subject variability of the coordination variables may indicate that the coordinative mode of the events (P1: flexion actions during downswing, P2: extension actions, and P3: flexion actions during upswing) are acquired. After such achievement, the intervention of the practitioner can be focused in the placement of the subsequent event.
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