# Handgrip Strength Time Profile and Frailty: An Exploratory Study
## 1 Introduction  
Population aging is a global phenomenon caused by a decline in fertility and an increase in life expectancy. As the number of elderly people grows, so does the prevalence of chronic diseases and frailty, challenging health and social services all over the world [1, 2]. Frailty is a state of high vulnerability in which minor stressors may lead to negative outcomes, such as hospitalization, disability, institutionalization or death [3]. It is caused by physiological age-related changes, by comorbidity, and, in some instances, by life-course determinants [4]. Although there is no consensus regarding the clinical presentation of frailty, the vast majority of researchers and clinicians agree that this condition may be prevented, reduced, or reversed [2, 5]. Consequently, the screening of frailty is crucial to ensure the dignity and quality of life of older populations. The present COVID-19 pandemic, with the imposed physical and social isolation, is contributing to an increase in frailty, in particular, among the elderly population, with an impact that will remain even after the pandemic crisis. As referred by [PERSON] [6], \"the irreversible spiral of the Frailty Syndrome\" needs to be prevented, fighting effects such as lack of activity, psychological stress, and physical distancing. Those features disturbing the emotional and affections balance will affect the elderly, who are especially vulnerableto social isolation and loneliness, which is accelerating and rising significantly worldwide during and will remain after the pandemic [7]. Therefore, detecting possible frailty states not only becomes highly important but also for following its evolution in the elderly. The use of an easy and quick screening system can be valuable. Having signaled an elderly person is more likely to enter a frail state, social or health care organizations can plan timely interventions or/and treatments, thus avoiding or slowing down the health deterioration process [8]. A common assessment of frailty is the biological model developed by [PERSON] [9]. It comprises the measurement of five physical components that compose the frailty phenotype: unintentional weight loss, exhaustion, low physical activity (self-report), slow walking speed (timed test), and decreased maximum value of handgrip strength (dynamometer measurement). In this operationalization, a person is considered frail if three or more components are positive. However, this approach is often contested for several reasons. First, the feasibility of measuring the components of the frailty phenotype in a busy daily routine is debatable [10; 11]. Consequently, measurements with fewer variables have been developed, such as the Study of Osteoporotic Fracture Criteria for Frailty (SOF) index [12], or measurements based only on self-report, such as the FRAIL scale [13]. Second, some authors argue that other measurements and adjusted score calculations can present a higher predictive validity considering the main outcomes of frailty (e.g., SHARE-FI [14]). Lastly, the unidimensional (i.e., entirely physical) approach to frailty is criticized for not considering that psychological and social factors can increase one's vulnerability. Consequently, biopsyychosocial measures have been developed, such as the Tilburg Frailty Indicator (TFI) [4; 15]. Maximum value of handgrip strength (HGS) is considered an important biomarker [16]. In fact, it is associated with overall health status, physical function decline, malnutrition and is a relevant predictor of all-cause mortality [17]. Several studies show that low HGS is associated with various indicators of frailty [18; 19] since it is a sign of overall muscle weakness and sarcopenia [20; 21], an age-related decline in muscle mass that leads to the loss of muscle fibers [22].