LAUSR

&NA; There is currently no test to directly and easily measure dynamic balance during walking in old adults. We examined the idea that distance of beam walking with and without cognitive dual‐tasking could detect age differences in dynamic balance. Healthy old (n = 16, 71.2 y) and young (n = 20, 22.0 y) volunteers walked 3 times on 4‐m long beams first without (single‐tasking) then with a calculation task (dual‐tasking) in order of decreasing beam width (12, 8, 4 cm). There was a Group (old, young) by Beam width (4, 8, 12 cm) by Task (single‐, dual‐tasking) interaction (F = 4.0, p = 0.026) for beam walking distance (primary outcome). Beam walking distance decreased similarly with decreasing beam width while single‐tasking (12 cm: 3.88 m, 8 cm: 3.62 m, 4 cm: 2.49 m) and dual‐tasking (12 cm: 3.87 m, 8 cm: 3.76 m, 4 cm: 2.59 m) in young adults. Beam walking distance decreased substantially and most on the narrowest beam while single‐tasking (12 cm: 3.85 m, 8 cm: 3.72 m, 4 cm: 1.46 m) but decreased even more on the two narrowest beams during dual‐tasking (12 cm 3.91 m, 8 cm: 2.63 m, 4 cm: 0.66 m) in old adults. Video analyses revealed that step length decreased in young while both step number and step length decreased in old adults. Beam width but not dual‐tasking affected young adults' beam walking distance whereas both beam width and dual‐tasking affected substantially and interactively old adults' beam walking distance and velocity. The results suggest that, if validated and cognitive performance also quantified, beam walking distance and walking velocity in single‐ and dual‐tasking conditions could be a diagnostic tool of walking balance and cognitive impairment in aging.