## 4 Discussion  
This study aimed to test an example of active aging by evaluating all age categories of runners over a period of 13 years in the 2007-2019 editions of the Venice Marathon (VM). In the VM, most participants were from Italy [19], and the total number of participants was lower than that of other marathons, such as those of New York (USA) and Berlin (Germany) [10; 11]. Despite this, analyzing a time span of 13 years of VM editions, the gender distribution and the increased participation of females were consistent with those shown in the Marathon Statistics 2019 worldwide report [20], which assessed the distribution of participants and marathon performances in 30 countries around the world by examining over 30,000 races held between 2008 and 2018 [20]. The increased participation in marathons resulted from a raised awareness of the importance of physical activity in adults, since it has been shown that regular physical activity at medium-high intensity improves health and facilitates bone remodeling [2]. Running is a relatively simple and easy physical activity to perform, either alone or in a group. Over time, the most important event in athletics--the marathon--has also become popular among amateurs, leading to the organization of recreational races that are open to professionals as well as to amateur or passionate athletes. In line with the findings of other authors [10], our analyses showed that the age categories of 40 and 45 years old were the most numerous among the participants, and the largest increases in participation were among women over 45 and men aged 65-70 years. As expected and previously reported, the analyses of performance showed a decline with increasing age [14; 21]. The best performances were always observed for both men and women in the 30-year age category, while the worst were observed in the oldest age categories--80 years old for men and 75 years old for women. The females generally performed worse in each age category, but the differences between genders were very small considering the mean speeds of AD13. Since the analyses in each age category included the running speeds of both winners and the last classified participants (who kept a walking pace), these results are more of social and cultural relevance than of sporting interest, as reported by [PERSON] and collaborators [22]. The details of the analysis of AD during the 13 VM editions showed a trend towards a decline in men's performance almost in every age category, from 30 years old onwards, while in women this decline was limited to the 30-35-year age category. The high number of recreational marathons in Italy and around the world has probably led to a greater selection of events in which to participate over time, and the VM could be less attractive for the younger amateurs. However, the analysis of the TOP performers showed a speed improvement in several categories, which was significant for the 35-40-year-old males and 40-year-old females. This may suggest that the marathon attracts mature men and women who continue to see improvements in their performance. The trends by gender observed in the AD13 and TOP13 analyses confirm that the age factor is a determinant in the performance decline. As reported in other studies [2; 23], eliminating all confounding characteristics--such as lifestyles that negatively affect running performance--our analysis shows that performance decline in trained athletes could be due to physiological changes that occur with aging. Even considering the interindividual variability, a heterogeneity of muscle size and strength responses was observed in trained individuals, with similarities between men and women in the same age groups [24]. This could suggest a homogeneous decrease in performance with age, until other factors such as the influence of hormones in women and different training regimens take over. Estrogens ensure the maintenance of trained muscles, fluid balance [25], nutrition, and energy intake [26]--all factors that change with age, especially in women [27; 28; 29].