BIOMECHANIC OF BALANCE:PARADIGMS AND PROCEDURES

Balance, like coordination, is understood by virtually everyone to be a critical component of skillful movement. Yet there exists very little biomechanical research into how balance is employed and improved by performers of disparate abilities in different sports. The purpose of this symposium is to open a dialogue on the biomechanics of balance. The first part of the symposium will be an exposition of definitions and conceptions of balance from the literature. While most of the traditional approaches provide clarity on some aspect of balance, not one is broad enough to encompass the diversity of contexts and proficiencies in sport. By combining features of many approaches and elaborating on the false dichotomies (e.g., static vs. dynamic), we propose a more contemporary conception of balance which deals with the interplay of stability and mobility of the body with respect to its base of support. Depending on the sporting context, more stability than mobility may be desired, and depending on the skill level of the performer, more instability than stability may be apparent. There are many ways to operationalize stability and mobility: for example, using video, we can measure the position and movement of the line of gravity with respect to the base of support, and using a force plate, we can assess the A/P and M/L forces and the center of pressure. The second part of the symposium will be an exploration of balance using the stability/mobility paradigm and procedures. Specifically we will compare intermediate and advanced performers in four sports skills: In the basketball jump shot, which requires great A/P stability over a small base of support, higher skill was associated with less in stability. In the volleyball spike, which requires arrested mobility as the horizontal approach is transformed into the vertical jump, higher skill was associated with greater reduction in mobility. In the golf pitch shot, which requires little mobility in either the A/P or M/L directions, higher skill was associated with less mobility. In the weight lifting snatch, which requires an early horizontal movement of the bar followed by relative stability, lower skill was associated with greater stability. Given that the snatch also has a perceptible risk of injury, this finding is not surprising. Following a summary, the audience will be invited to participate in a discussion on the biomechanics of balance