Gait phase proportions in different locomotion tasks: The pivot role of golden ratio.

Walking is a repeatable and cyclic locomotor act, presenting standardized biomechanical patterns within the gait cycle in healthy humans. Specifically, both stance and swing durations exhibit high reliability at comfortable speed, maintaining the same proportion between the twos with respect to different contextual features in forward walking. Recently, it was found that this proportion is close to the "golden ratio" (a well-known irrational number equal to 1.618…). While few studies analysed how this ratio is modified due to different contextual factors, no studies are available about different locomotor acts. Thus, aim of the study is to verify whether and how the stance-to-swing ratio is modified during the execution of different locomotor tasks. Twenty healthy young subjects were asked to perform different tasks: forward walking, backward walking, lateral walking, stepping in place, stair ascending and descending, while wearing baropodometric shoe insoles. All tests were performed at comfortable speed, while forward walking was also tested at slow and fast speed. The stance-to-swing ratio did not differ significantly from the golden ratio in forward comfortable walking, backward walking and stair descending. A cluster analysis identified the most frequent cluster centered at 1.63, a value close to the golden ratio. These results supported the idea that golden ratio is the preferred stance-to-swing ratio modality, but at the same time this ratio could be adapted in response to particular contextual requests.