## 1 Introduction  
Fall events in the elderly challenge public healthcare due to the high social and economic impact. The prevalence of fall events is increasing among the elderly (from 16.3 to 21.3% around the world) [1], leading to hospitalization, disability, and mortality [2]. The World Health Organization (WHO) estimates that globally around 660,000 falls among adults result in fatal events. Age is considered to be the major risk factor inducing falls in people aged 60-65 years old. Older adults often show age-related chronic conditions and comorbidities [3] that further affect their physical fitness in activities of daily life (ADL), making them more vulnerable to the risk of falling. Moreover, fall history generates fear of a second fall, reducing progressively all the ADL resulting in social isolation, anxiety, and depression. This brings a substantial weakening of physical fitness that increases the fall risk, disability and hospitalization or institutionalization [4]. Fall events are also involved in driving up medical costs worldwide. The economic impact on medical services in managing the consequences of falls run into billions, including hospitalization time, medical treatment, and long-term care services [5]. Due to the increase in fall events, healthcare stakeholders should increase prevention strategies directed at the elderly, with the aim of identifyingfall-associated risk factors [6]. Population-based studies have shown that more than 30% of community-dwelling people over 65 years, and up to 50% of people who live in long-term care institutions fall at least one time during their life [7,8]. The fall risk further increases in people, women especially, over 75 years old [9]. Among all falls, 5% lead to fractures, lacerations, or hospitalization [10]. Fall events occur more frequently in clinical settings rather among the community-dwelling elderly [8,11]; however, although independent, the community-dwelling elderly are more susceptible to environment and home barriers and, thus, to fall [11]. The risk factors associated with fall events are (i) muscular and mobility alterations (especially with health equipment, such as walking aids and wheelchairs) [12], (ii) knee and/or hip osteoarthritis [13], (iii) sarcopenia [14], (iv) dementia, (v) comorbidity and poli-therapeutic treatment [15], (vi) fall events history. In addition, fall events in the elderly are associated with many variables and predisposing factors [2,16]: some clinical age-related conditions (i.e., vestibular, proprioceptive and visual disorders, cognition and musculoskeletal alterations, also at molecular level, etc.) and environment-related factors, such as home barriers, unsuitable shoes, etc. [10,17-10]. The aging process is also associated with frailty, a geriatric condition that further increases the vulnerability of elderly especially during ADL--such as dressing, feeding, personal hygiene, telephone use, home maintenance, etc. [21]. Frailty has already been linked with a higher prevalence of falling risk in old people [22]; however, there is no consensus in diagnosing the condition of frailty [23]. Fall events and frailty often impact the independent daily routine, generating fear of a second fall event and, consequently, a general mobility reduction, depression, anxiety, and social isolation. Quality of life in general is negatively affected; thus, prevention strategies should be planned as much as possible [24]. The elderly show gait alterations, a physiological deterioration in postural control mechanisms (interaction of musculoskeletal, sensory, and neuromuscular systems) and body orientation [25], reduced strength, and muscle tone [26,27]. Studies evaluating the proprioception and vestibular activity in response to external stimuli reported a reduction in the abilities of the elderly (people aged over 60) while coping with some destabilizing perturbations of posture (both visual stimuli such as shutter goggles, and mechanical vibrations applied to various parts of the body) [28,29].