The Ramp protocol: Uncovering individual differences in walking to an auditory beat using TeensyStep

Abstract

Intentionally walking to the beat of an auditory stimulus seems effortless for most humans. However, recent studies revealed significant individual differences in the spontaneous tendency to synchronize to the beat. Some individuals tend to adapt their walking pace to the beat while others show little or no adjustment. However, to date, there is no protocol sensitive to individual differences in adapting to rhythmic stimuli while walking that can experimentally validate this phenomenon. To fill this gap, we introduce the Ramp protocol assessing spontaneous adaptation to a change in an auditory rhythmic stimulus in a gait task. First, participants start to walk at their preferred cadence without stimulation. After several steps, a metronome is presented, timed to match the rhythm of the participant's heel strike. Then, the metronome tempo progressively departs from the participant's cadence by either accelerating or decelerating. The implementation of the Ramp protocol required real-time detection of heel strike and auditory stimuli aligned with participants' preferred cadence. To achieve this, we developed the TeensyStep device, which we validated compared to a gold standard for step detection. We also demonstrated the sensitivity of the Ramp protocol to individual differences in the spontaneous response to a tempo changing rhythmic stimulus by introducing a new measure: the Response Score. In sum, this new method and quantification of spontaneous response to rhythmic stimuli holds promise for highlighting and distinguishing different profiles of adaptation to an external rhythmic stimulus in a gait task.