## 4 Discussion  
The objective of this study was to investigate and measure the alterations in physical fitness among urban Catalan adolescents spanning a 20-year period (2002-2022). The primary outcome revealed a notable decline in the performance of the 8 \(\times\) 10 m shuttle run test over the past two decades, observed in both male and female participants. This decline suggests a deterioration in the physical agility of adolescents during this timeframe. The observed decline in the 8 \(\times\) 10 m test performance over the past two decades aligns with findings from various studies indicating a gradual deterioration in the overall physical condition of adolescents compared to previous generations [40; 41; 42; 43; 44; 45]. Although no single factor can fully account for the downward trend in agility performance observed in this study, it is likely influenced by a combination of environmental, social, behavioral, physical, psychosocial, and physiological factors [11; 40; 46]. Among these factors, the rise in obesity rates among the youth population stands out as a significant contributor to declining physical fitness [47]. Changes in body composition have often coincided with alterations in physical fitness levels in many countries [48; 49]. Globally, the prevalence of overweight and obesity among children and adolescents has surged, particularly in industrialized nations, posing a significant public health challenge [50]. Southern European countries have witnessed a concrete and notable increase in rates of overweight children [51]. This obesity epidemic has become a pressing concern in the twenty-first century due to its substantial healthcare costs [52; 53]. Obesity, characterized by an imbalance between caloric intake and expenditure, leads to the accumulation of body fat, resulting in various physiological disorders such as dyslipidemia, diabetes, and certain types of cancer [54]. Additionally, it can contribute to psychological and social issues such as low self-esteem, depression, and antisocial behavior [55]. While there is no singular factor responsible for obesity development, physical inactivity is closely associated with poor physical fitness [56]. In terms of agility performance, [PERSON] et al. [57] observed that overweight adolescents tended to fare worse in tests requiring the propulsion or elevation of body mass, such as the 8 \(\times\) 10 m test. Another factor potentially contributing to the decline in adolescents' agility could be the widespread use of technology. While technology offers significant educational and communicative benefits, its inappropriate or excessive usage can have detrimental effects on adolescents. In recent years, the prevalence of technology use, including social networks, the internet, smartphones, video games, and television, has skyrocketed. According to the National Institute of Statistics (Spain), 91.8% of children aged 10 to 15 are regular internet users, with a substantial proportion spending more than 4 h per day in front of screens, doubling the recommended limit [58]. Nationally, data from the Pfizer Foundation indicate that 98% of Spaniards aged 11 to 20 use the internet, with 70% spending over 1.5 h online daily [59]. The extensive time spent on technology by children and adolescents is concerning as it is considered a sedentary behavior that competes with physical activity for leisure time [60]. This sedentary lifestyle resulting from excessive technology use may lead to a decline in physical activity performance [61]. In contrast to evidence suggesting a general decline in physical fitness, some countries have reported positive trends in specific components of physical fitness. For instance, in Finland, an increase in muscular fitness has been observed among adolescents aged 13 to 16 over a 25-year period from 1976 to 2001 [62]. Similarly, in Canada, there has been a notable increase in cardiorespiratory fitness and strength [63], which may be attributed to the country's additional exercise programs at schools.