Abstract
The harmonic structure of walking relies on an irrational number called the golden ratio (ϕ): in healthy subjects, it coincides with the stride-to-stance ratio, and it is associated with a smooth gait modality. This smoothness is lost in people with Parkinson’s disease (PD), due to deficiencies in the execution of movements. However, external auditory cues seem to facilitate movement, by enabling the timing of muscle activation, and helping in initiating and modulating motor output. Based on a harmonic fractal structure of gait, can the administration of an auditory cue based on individual’s ϕ-rhythm improve, in acute, gait patterns in people with PD? A total of 20 participants (16 males, age 70.9 ± 8.4 years, Hoehn and Yahr stage-II) were assessed through stereophotogrammetry: gait spatio-temporal parameters, and stride-to-stance ratio were computed before, during, and after the ϕ-rhythm administration. Results show improvements in terms of stride length (p = 0.018), walking speed (p = 0.014), and toe clearance (p = 0.013) when comparing gait patterns before and after the stimulus. Furthermore, the stride-to-stance ratio seems to correlate with almost all spatio-temporal parameters, but it shows the main changes in the before–during rhythm comparison. In conclusion, ϕ-rhythm seems an effective cue able to compensate for defective internal rhythm of the basal ganglia in PD.
Highlights
Parkinson’s disease (PD) is a chronic, neurologic disorder which primarily results from the death of dopaminergic neurons in the substantia nigra pars compacta, leading to dopamine deficiency
This deficiency is responsible for the major PD motor symptoms [1], which usually appear as tremor at rest, akinesia or bradykinesia, rigidity, and postural instability [2]
Our results confirm that the use of an auditory cue produces immediate effects on several gait variables: as previously reported in the literature, people with PD display particular difficulty with the internal stride length regulation, showing an increase in step cadence to compensate for the reduced step size and gait speed [13]
Summary
Parkinson’s disease (PD) is a chronic, neurologic disorder which primarily results from the death of dopaminergic neurons in the substantia nigra pars compacta, leading to dopamine deficiency. This deficiency is responsible for the major PD motor symptoms [1], which usually appear as tremor at rest, akinesia or bradykinesia, rigidity, and postural instability [2]. These features are known to affect gait of people with PD, which is usually characterized by decreased foot clearance, reduced stride length and gait velocity, increased stance phase, and greater forward inclination of the trunk, compared to age-matched controls [3,4]. Harmonic properties of locomotor patterns facilitate the gait rhythm control, that can be activated and regulated by serotonergic neurons projections of the brain stem [6]
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