Emergent perception-action couplings regulate postural adjustments during performance of externally-timed dynamic interceptive actions.

Studies of postural coordination during performance of externally-timed interceptive actions, such as catching a ball, have been infrequent, with advanced visual information from a thrower's actions towards a catcher, typically excluded in experimental task constraints. Yet previous research suggests that manipulating participant access to such information alters their hand movements and gaze behaviours when catching. In this study, we manipulated participant access to advanced information of a thrower's actions, and from ball flight, while recording whole body kinematic and kinetic data to investigate effects on postural control during performance of interceptive actions. Twelve participants attempted to make or simulate performance of one-handed catches in three experimental conditions: when facing integrated videos of advanced visual information and ball flight only, videos of a thrower's actions only, and of ball flight only. Findings revealed when integrating advanced visual information and ball flight, and when participants were provided with ball flight information only, lower limb adjustments were primarily used to regulate posture. However, movement was initiated earlier when advanced visual information was available prior to ball flight, resulting in more controlled action and superior catching performance in the integrated condition. When advanced visual information was presented without ball flight, smaller displacements were observed in lower limb joint angles, resulting in upward projection of the centre of mass, compared to a downward trajectory when ball flight information was available, in the integrated video and ball flight, and ball-flight only conditions. Results revealed how postural coordination behaviors are dependent on specific informational constraints designed into experiments, implying that integration of task constraints in studies of human perception and action needs careful consideration.