## 1 Introduction
In general, body movement can be monitored using several different technologies, with the optoelectronic ones being considered as the gold standard, which are mainly based on infrared cameras. However, because of drawbacks such as high costs, dedicated rooms, and the necessity of experienced personnel, other technologies have been emerging. Therefore, depending on the particular body movement to be measured, different solutions have been proposed: photoplethysmogram (PPG), ballistocardiogram (BCG), seismocardiogram (SCG) for measuring respiratory rate [4]; WiFi and radio detection and ranging (RADAR) for activity recognition [5]; and wearable technology--based on inertial measurement units (IMUs) [6], flexible sensors [7], insole pressure sensors, or electromyography sensors--for gait analysis [8, 9]. Within the frame of clinical or general performance evaluations [10, 11, 12, 13, 14, 15], temporal gait analyses are nowadays used to complement the classical gait analyses that involve motion analysis, dynamic electromyography, force plate recordings, energy cost measurements, and measurement of the stride characteristics [16, 17, 18]. Indeed, four time intervals--namely, the ones associated with the durations of the gait cycle, swing, stance, and double support phases--temporally characterize symmetric and recursive human walking [16]. An innovative research direction, promoted by [19], has emerged from most of the literature agreeing that the foot off reliably occurs at 60% to 62% of a physiological gait when the subject is (symmetrically and recursively) walking at a comfortable speed: the analysis of the ratio between the swing and double support phase durations has experimentally recognized it as close--in healthy subjects symmetrically and recursively walking at about 4 km/h [20], but not in patients affected by neurological disorders--to the golden ratio \(\phi=(1+\sqrt{5})/2\approx 1.618\), i.e., the positive solution to the equation \(x^{2}=1+x\) (see [21]). Such an irrational number, which is related to [PERSON]'s problem of cutting in a self-proportional way a given straight segment, thus captures:  
* Self-similarity features in symmetric walking of healthy subjects; and
* A reduction of the smooth, graceful and melodic flow of movement in the altered gait of patients (e.g., patients with Parkinson's Disease, known to be characterized by a tremor at rest, rigidity,kinesia or bradykinesia, and postural instability [22]; patients with cerebellar ataxia [13] (for patients with cerebellar ataxia and healthy subjects, energy consumption during walking is shown to be minimized when they walk with a gait ratio close to the golden ratio [13]), or patients with stroke [23]). Now, symmetry and harmony are strictly intertwined in walking. Two comprehensive indices in ref. [24,25] have been, accordingly, recently suggested to simultaneously characterize these two important features. In particular, ref. [25] has provided original mathematically founded arguments to a fractal approach to the question (the generic idea that walking can have a fractal structure can be found in [26], while the existence of significant alterations from such a structure in patients with Parkinson's Disease has been suggested in [27]): the larger scale structure resembles the subunit structure through the generation of a self-referential loop (see Refs. [28,29] for relevant applications to swimming). Human walking is, then, innovatively described in terms of generalized finite length Fibonacci sequences [30] and dynamics on graph concepts, with the new mathematical concept of a _composite gait cycle_--involving two specific couples of overlapping gait cycles, namely, the left and right gait cycles and the _adjoint_ right and left gait cycles--to extend the idea of stride to stride intervals [31] and step-by-step intervals [32]. The aim of this paper is to present the reliability of a technologically assisted methodology--performed with an easy to use wearable motion capture system--in assessing motion abilities in AT.