# Trend Forecasting in Swimming World Records and in the Age of World Record Holders
## 1 Introduction  
Success in competitive swimming requires a clearly defined pathway of progression to deliver the best performances in adulthood. In the past, several backscatter strategies have been implemented to help swimmers have a longer and more sustainable career. The implementation of Long-Term Athletic Development models [1, 2] or performance monitoring over swimmers' careers [3, 4, 5] contributed to understanding how swimmers behave over the years and how they may improve in the long-term. Moreover, the determination of normative data and percentile curves [6] and the comparison of age-related performance progression against top athletes [7] have also been used for tracking swimmers headed toward future success. At some point in a swimmer's career, there will be stabilization in their performance near the peak. The age range between 15 and 16 years has been considered a determinant for achieving the best individual performance in long-distance events [8]. Males' peak individual performance seems to occur between 18 and 19 years for short-distance specialists and between 17 and 18 years for long-distance specialists [9]. The analysis of overall trendsand the individual paths of performance over a decade showed deceleration around the age of 16 years [4], with the peak performance being reached around 18-19 years for young adults [10]. World-class performances are also highly dependent on swimmers' sex. [PERSON] et al. [7] concluded that top male swimmers achieved peak performance \(\sim\)2 years later than their female counterparts. This difference in age of peak performance between sexes appears to be explained almost entirely by the \(\sim\)2-year earlier onset of puberty in females compared with males [11]. However, during recent decades, the improved performance of elite female athletes has narrowed the gap by 8 to 12% compared to male athletes [12]. Despite that, some genetic traits related to athletic development and peak performance will always persist [13], not allowing for the complete disappearance of this gender gap. As swimmers grow older, they may become unwilling or physiologically unable to sustain the training loads required to achieve top performances in their events. Although these swimmers may endure the training loads, the continuous training stress may increase their susceptibility to injury [14]. This scenario could result in a premature peak in performance, leading to a career break or a drop-out. As a consequence, most of these decisions are taken to pursue other challenges like parenting, pursuing an academic/professional career, or even just recovering from the emotional or physical exhaustion induced by training [15]. Still, if they return to practice a few years later, they can compete at an elite level (e.g., [PERSON], [PERSON], or [PERSON]). Recent top-level performances in shorter distances (including some in World and Olympic events) were achieved by swimmers who were over 30 years old (e.g., [PERSON], [PERSON], [PERSON], [PERSON], [PERSON]). It seems that some of today's top-ranked swimmers are winning at a more advanced age than their previous counterparts. [PERSON] et al. [16] found that the age of peak performance of World and Olympic champions competing between 1992 and 2013 was \(\sim\)2-3 years older compared with Olympic gold medal winners (aged \(\sim\)21 and \(\sim\)23 years) from 1896 to 1980. [PERSON] et al. [17] also found that the age of peak swimming speed for elite female swimmers increased in the 50 m freestyle from 1994 to 2012. World records in long-course freestyle swimming have constantly improved over the decades, influenced by changes in training practices and/or technology. However, it remains unclear if there is a preference in the age of world record holders across different types of freestyle events (short-distance vs. long-distance). Studying world record dynamics based on historical data can provide insights into world record trends and whether they differ by sex and event type.