Expertise in sport results from the adaptation of behavoirbehavoir to interacting constraints, individually per-ceived and encountered. With this emphasis on intentionality, perception and action to constrain behavoirbehavoir, the role of movement pattern stability, functional intra-individual and inter-individual performance variability is paramount. Here we illustrate these ideas with reference to two individual performance environments: ice climbing and breaststroke swimming. In ice climbing, compared to beginners, expert climbers exhibited greater levels of variability in upper- and lower-limb coordination patterns, exploring a larger range of limb positions and movement types (ice tool swinging, ice hole hooking). Ice fall properties contain affordances that induced variable motor coordination patterns in expert climbers, whereas learners used a basic and functionally stable motor organization to achieve their main goal of maintaining body equilibrium with respect to gravity. In swimming, while learners organized their limbs to advance in the water, their main intention was to balance, float, breathe, and perceive information. For these reasons they typically adopted one stable (in-phase) mode of arm-leg coordination whatever the swim speed. In contrast, experts harnessed available environmental and organismic constraints (strength, flexibility relative to aquatic resistance and the Archimedes principle) to satisfy a key performance constraint (swim fast). To achieve this aim, they varied the arm-leg coordination mode within a stroke cycle and swim speed. Together these data illustrate how functional performance in sport is predicated on the intertwined rela-tionship between intentions, actions and perceptions of each individual, requiring a blend of stable and variable movement patterns to satisfy changing task constraints.