Practice variability refers to the variety of movements, tasks and context the individual experiences during practice and is important in skill acquisition because of the increase in useful information for the movement system it provides through an enlarged and enriched sensorimotor mix.
An increase in variety is a method to increase stochastic noise through fluctuations. The noise amplifies the signal strength of feedback, which as a result now exceeds the threshold value of the motor system. Through the added noise information about effective movement and solutions can be stored in the system. With this information the movement system now slowly assembles strong configurations of synergies and effective performance. The increase of fluctuations will also affect error sensitivity of existing synergies positively.
Synergies represent an organization of degrees of freedom and are strong, task specific, coordinative structures that result in stable and simultaneously flexible movement. Synergy elements are strongly linked so errors or perturbations in one of the elements are automatically corrected by other elements of the synergy. Through an self-organizing configuration the system can exploit internal and external forces, errors and perturbations more effectively hence efficiency and stability in performance increase.
Practically thought it is important to stress variety itself provides no information about movement effectiveness. For the movement system to learn and grow there must be a strong link between de movement and the desired end result. This observation shows the importance of very clear end points and result-oriented feedback within training and variations.
Brief take home: Application of practice variability in a task-specific, related setting, with clear end points and knowledge of result feedback can be seen as grist on the mill of learning and training motor skills.
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