Variability in neurobiological systems and training

In this brief review of functional movement variability in sport, it has been demonstrated that both inter- and intra-individual variability is an inherent feature of performance across the broad continuum of expertise. The enhanced focus on variability in movement at an individual level has resulted from changes in theoretical influences in the literature on motor control and from advances in data collection and analysis techniques. The existence of inter-individual variability implies that there is no optimal movement pattern for a given activity and that movement expertise is a reflection of the performer’s ability to adapt to dynamic constraints. Intra-individual variability shows us that an individual must recipro­cally link their actions with relevant environmental information to consistently achieve performance outcomes. Characterizing learners as complex, biological systems promotes awareness by practitioners that a learner’s coordination solutions are the products of self-organization and that periods of movement variability (or instability) should be valued as part of the learning process (Chow et al. 2007). To encourage acquisition of functionally relevant coordination solutions performer-environment interactions should be manipulated through altering relevant task, environmental and performer constraints. Thereby, constraints operate on different timescales, which has important implications for the practitioner’s judgment of the learner’s rate of progress. When learning a new coordination pattern, more permanent behavioural changes take longer to appear than immedi­ate adaptations to task constraints during practice. Practitioners should understand that some behaviours might represent transient adaptations to immediate task constraints imposed during practice, which interact with organismic constraints related to developmental status (Seifert et al. 2013). A struggling learner can be viewed as a system that is temporarily trapped in a stable attractor state that does not correspond well with a behavioural solution satisfying task demands. As Davids et al. (2008) suggest to practitioners, a strategy of perturbing the movement system may be necessary to help the learner to let go of previous movement experiences. Techniques such as altering task constraints like rules, space, equipment and number of opponents are useful ways to induce variability in movement and encourage exploration for alternative information sources and movement solutions. Note that the learner may need additional encouragement and reassurance at this important stage, as performance could fluctuate as a consequence of the perceptual-motor reorganization. In this chapter, we have demonstrated the value of employing individualized analyses in research on movement to gain a clearer picture of how performers exploit variability. As more studies employ methods such as coordination profiling and cluster analysis, researchers are becoming increasingly convinced that varied movement trajectories emerge from the interplay among the specific task, environmental and organismic constraints unique to each situation. This is particularly apparent within sport, where such factors change frequently and unexpectedly. As we have demonstrated, expert performers are increasingly recognized as having an ability to continually adapt their techniques as perceptual demands change. The mechanisms by which humans progress to this level of control as a function of learning or relearning provide a fruitful focus for future research.