Let “play” and “practice” represent 2 different modes of engagement with a given physical task. Where practice points at a pursuit of improvement, play becomes both a testing grounds for that improvement as well as the cathartic moment into which practice empties itself (the teleology of the practice; a non-verbal “why” for the “what” of practice).
This makes both critical in full development, but also extremely distinct. As such, they should be approached with awareness of the characteristics of each – both the characteristics they share, and those they do not (an awareness that comes from exposure to both). For example, they do not share the same kind of parameters: in practice, we can adjust the level of challenge (do this faster, or with more constraints) to just beyond the levels of comfort, in order to achieve adaptation. Not so in play. Play doesn’t force adaptation on the same level; it causes it one level beyond – in the ability to play, in the ability to reveal those practiced skills in the moment (but it requires a sufficiently evenness between “players”). It would be a mistake to play with the practice ethic, and vice versa to practice with a play ethic.
In addition to where there is no overlap, we can see areas where they do- for example, that the “full-on” attitude, approaching the work with intensity, can (should) be present in both. That is, it is not intensity which differentiates play from practice. Full-on practice is deliberate practice (instant feedback, substantial mental strain), and full-on play is the dog on a bone. As such, dicking around would not be looked upon as a high level of physical activity, whether as play or practice (though as play it can serve a fulfilling contribution to social needs, which we may be apt to neglect).
This kind of dichotomization may represent the worst of hierarchical thinking, but hey… if you don’t have windows to break, what you gonna do with them bricks?