EFFECT INITIAL FOOT POSITION HAS ON WEIGHT DISTRIBUTION SYMMETRY AND FORCE PRODUCTION DURING A SIT-TO-STAND TASK IN OLDER ADULTS

Abstract

INTRODUCTION AND AIMS Transitioning from a seated position to standing is an important component to everyday living which can be affected by age-related muscle strength loss. Changing foot position has been found to affect a sit-to-stand transition in healthy younger populations however the effect it has on healthy older populations is unknown. The aim of this study was to provide clinicians with greater insight into the effect asymmetrical initial foot positions have on weight distribution symmetry and force production during a sit-to-stand transition in adults over 60 years of age. METHODS Three symmetrical and six asymmetrical initial foot positions were investigated on two separate testing sessions. The maximum vertical ground reaction forces collected from each foot placed on individual Kistler force platforms were used to calculate body weight symmetry percentage. RESULTS Body weight symmetry reduced when the dominant foot was moved posteriorly 1/3 and 2/3 participant’s foot length compared to the symmetrical positions (102-107%). When the non-dominant foot was moved posteriorly by 1/3 and 2/3 the participant’s foot length, body weight symmetry increased (99-102%) above the symmetrical positions. Maximum vertical ground reaction forces occurred (5.6-6.2N/kg) in the asymmetrical positions with the anterior foot positioned in neutral. CONCLUSIONS Asymmetrical foot positions which involved shifting one extremity posteriorly by 1/3 or 2/3 the participant’s foot length reduced transitional stability but increased force production. These results will help guide clinicians to scaffold progressions when prescribing sit-to-stand exercises to rehabilitate unilateral strength deficiencies within an older population.