## 1 Introduction
The elderly also show a reduction in foot sensitivity and plantar pressure, affecting both standing and walking performance [30]. Posture and balance control become impaired during aging; the amplitude and frequency of body sway increase as compared to young adults, probably due to an impaired activation of agonist-antagonist muscles [29,31]. More generally, a reduction in the integration of recruited systems controlling posture characterizes the aging process [32]: among these, a visual-dependent behaviour while standing was associated with an elevated falling risk in the elderly, even if this dependency may vary among subjects and posture can be modulated through many other variables [33,34]. Gait disturbance prevalence increases about 10% among subjects aged 60-69 and is more than 60% in community-dwelling people in their eighties [35]. Both neurological and musculoskeletal alterations could negatively affect gait performance (i.e., ataxia due to polyneuropathy, vascular parkinsonism and encephalopathy with frontal gait disorders, dementia, schizophrenia, and hip and knee osteoarthritis) [36,37]. Gait parameters are indeed predictive of the health status of the elderly, and that is also influenced by age, behaviour, and state of mind [38]. The elderly that frequently fall have a reduced reaction time in response to the unexpected (unforeseen obstacles, environmental barriers, etc.) [7,39] and this could reduce their autonomy in the ADL, with a subsequent risk of hospitalization, disability and/or mortality. If impaired, gait and balance control mechanisms are predisposing factors to fall events [24,40]. Aging is thought to be characterized by increased postural instability in walking performance and altered gait cycle parameters: shorter stride and step length, an opposite trend between stance and swing phases (longer stance/shorter swing phase) [41], and reduced height from the floor during the swing phase [42]. Gait speed (m/s) has been shown to decrease by 1% per year, due to a reduced step length without any change in gait cadence (steps/minute). The reason could be attributed to proprioceptive along with visual signals, and musculoskeletal disorders. Differently to younger people, the elderly have a reduced ankle range of movement (ROM) and strength, for which they exhibit more proximal--mainly hip--compensatory mechanisms, due to the decreased distal limbs proprioception [35; 43]. Performing posture and gait analyses for the early screening of fall risk is well established in literature. However, recent research stated that a single test could not discriminate between fallers and non-fallers, but a comprehensive evaluation of physical performances could be predictive of fall risk [44]. Among these functional tests, the timed up and go (TUG) is frequently administered to assess the ability to stand from a chair in combination with 3 m walking and returning to sit again. Nevertheless, the supporting evidence for TUG's ability to predict falls still seems inconsistent [44; 45]. Gait parameters, as gait speed, can be examined with the six-minute walking test (6 MWT) and the 10 m walking test (10 MWT) that verify the walking performance of the elderly. The completed distance and time of both tests respectively show the degree of functional disability, especially related to the lower extremities; of note, the detected walking speed, if reduced, is associated with increased mortality [45]. There are several evidence-based protocols aimed at preventing the risk of falling [46], by contrast, frailty is more difficult to diagnose [23; 47]. Screening interventions mainly consist of self-reported questionnaires [48] by which lifestyles, the amount of physical activity, nutrition, psychological and social attitudes [49] are assessed and evaluated for early recognition of falling risk and/or frailty conditions. Exercise programmes improving balance and strength are also available as home-based interventions or in a clinical setting [50; 51] as prevention protocols.