Implicit advance knowledge effects on the interplay between arm movements and postural adjustments in catching

This study examined if, and how, implicit advance knowledge of upcoming ball speed influences the interplay between arm movements and concomitant postural adjustments in one-handed catching. While standing, subjects were asked to catch balls that were presented with or without implicit advance knowledge of four different ball speeds. Full body kinematics and ground reaction forces were measured, which allowed the assessment of arm movements and postural adjustments through the momentum of the arm, rest of the body and whole body. Providing implicit advance knowledge induced a forward arm raising movement scaled to ball speed in the initial transport phase. However, the accompanying backward postural adjustments were unaffected, which is suggestive of a passive control mechanism. In the subsequent grasping phase, the scaling of arm raising movement exhibited in the presence of implicit advance knowledge resulted in a reduced need for postural adjustments, particularly at the highest ball speed. Together, these findings suggest that cortical involvement based on previous experience not only shapes the arm movements but also the subsequent interplaying postural responses.