RESEARCH ARTICLE Jeffrey M Hausdorff Æ Galit Yogev Æ Shmuel Springer Ely S. Simon Æ Nir Giladi Walking is more like catching than tapping: gait in the elderly as a complex cognitive task Received: 19 October 2004 / Accepted: 11 January 2005 / Published online: 28 April 2005 Ó Springer-Verlag 2005 Abstract Walking is generally viewed as an automated, over-learned, rhythmic motor task and may even be considered the lower-limb analog of rhythmic finger tapping, another automated motor task. Thus, one might hypothesize that walking would be associated with a simple rhythmic task like tapping rather than with a complex motor task like catching. Surprisingly, however, we find that among older adults, routine walking has more in common with complex motor tasks, like catching a moving object, than it does with tapping. Tapping performance, including both the average tapping interval and the variability of tapping interval, was not significantly associated with any gait parameter (gait speed, average stride time and stride time variability). In contrast, catch game performance was significantly associated with measures of walking, suggesting that walking is more like catching than it is like tapping. For example, participants with a higher gait speed tended to have lower times to first move when catching, better catching accuracy, and less catching errors. Stride time variability was significantly associated with each of the measures of catching. Par- ticipants with a lower stride time variability (a more steady gait) had better catching accuracy, lower time to first move, fewer direction changes when moving the cursor to catch the falling object, and less catching er- rors. To understand this association, we compared walking performance to performance on the Stroop test, a classic measure of executive function, and tests of memory. Walking was associated with higher-level cognitive resources, specifically, executive function, but not with memory or cognitive function in general. For example, a lower (better) stride time variability was significantly associated with higher (better) scores on the Stroop test, but not with tests of memory. Similarly, when participants were stratified based on their per- formance on the Stroop test and tests of memory, stride time variability was dependent on the former, but not the latter. These findings underscore the interconnec- tedness of gait and cognitive function, indicate that even routine walking is a complex cognitive task that is associated with higher-level cognitive function, and suggest an alternative approach to the treatment of gait and fall risk in the elderly. Keywords Gait Æ Cognitive function Æ Aging Æ Rhythmicity Æ Variability Background As suggested by the title of one of the classic texts on gait, ‘‘Muscles, Reflexes and Locomotion’’ (McMahon 1984), the general dogma is that walking is a ballistic, automatic motor task. Decerebrate cats walk (Burke et al. 2001; Shefchyk and Jordan 1985), supported newborns move their legs in a normal walking pattern (Lamb and Yang 2000), and adults ambulate with ease even as they juggle cognitively demanding tasks. Apparently, central pattern generators (Burke et al. 2001; Lamb and Yang 2000; Shefchyk and Jordan 1985), or their equivalents, create the rhythm and gait proceeds J. M Hausdorff (&) Æ G. Yogev Æ S. Springer Æ N. Giladi Movement Disorders Unit, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel E-mail: jhausdor@bidmc.harvard.edu Fax: +1-972-36974911 J. M Hausdorff Division on Aging, Harvard Medical School, 643 Longwood Ave., Boston, MA, USA J. M Hausdorff Æ G. Yogev Æ S. Springer Æ N. Giladi Department of Physical Therapy, Sackler School of Medicine, Tel Aviv, Israel E. S. Simon Department of Clinical Science, Neurotrax Corporation, New York, NY, USA N. Giladi Department of Neurology, Sackler School of Medicine, Tel Aviv, Israel Exp Brain Res (2005) 164: 541–548 DOI 10.1007/s00221-005-2280-3