HUMAN STANCE STABILITY IMPROVES WITH THE REPETITION OF THE TASK - EFFECT OF FOOT POSITION AND VISUAL CONDITION

The effects of repetition of quiet stance trials on body sway, recorde d through a stabilometric platform, were studied in 12 normal subjects . With feet together, both with eyes open (EO) and closed (EC), a prog ressive shift forward of the centre of foot pressure (CFP) occurred wi th repetition. In addition, with EC, but not with EO, a significant pr ogressive reduction in sway area (SA) and sway path (SP) occurred. Wit h feet 10 cm apart, initial SA and SP values were significantly smalle r than with feet together, regardless of the visual condition, but rep etition of trials induced no significant effects on either position of CFP or body sway under either visual condition. Results indicate the occurrence of a learning phenomenon in this simple postural task, wher eby the body shifts towards a 'safer' position with a minimum energy e xpenditure due to reduced corrections of sway. Forward leaning and dec rease in sway are two independently-occurring processes, each possibly due to a better central integration of proprioceptive input with repe tition of trials. (C) 1997 Elsevier Science Ireland Ltd.