Attentional demands and postural recovery: The effects of aging

Background. Cognitivedemandsassociatedwithbalanceand locomotionmay contributeto the incidenceof fallingamong older adults.'This studyaddressedissues relatedto the effectsof aging on the attentional demandsof recoveringfrom an exter-nal disturbanceto balance.'Thisresearchalso investigated whetherperforminga secondarycognitivetask differentially affects posturalrecovery in youngversusolderadults. Method. Fifteenyoung and 10healthy older adultswere exposed to a seriesof balance disturbances.Attentionaldemands were assessedusing a dual task paradigm whereposturalrecoveryserved as the primarytask, and countingbackwardsserved as a concurrentsecondarycognitive task.The effectof the countingtask was assessedby comparingkinematicvariables related to feet-in-place and steppingrecoverystrategies. Results. Recovering uprightstancewas foundto be attentionally demandingin both age groups.The type of recoverystrat-egy did not influence attentionaldemands in youngadults;however, a hierarchyof increasingattentionaldemandsbetweenthe ankle strategyand compensatory steppingwasapparentamongolder adults.In addition, steppingappearsto be moreattention-ally demandingfor older adults than for youngeradults.Countingbackwardsdid not affectthe type of strategyused;however, it did affectthe kinematicsof stepping.For both age groups,stepsoccurredwhen thecenterof masswas locatedin a morecen-trallocation withinthe base of supportwhen the secondary task was added. Conclusions. The abilityto recovera stableposturefollowingan externalperturbationis more attentionallydemandingfo